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Jorge Pullin: Okay, so I think we can start today we have a panel on the future or Luke quantum gravity bianca Dietrich Simone, especially from a seaman an end Wilson Ewing it's going to be chaired by by str so a bike could you take over from here.

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Abhay Vasant Ashtekar: Right so.

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Abhay Vasant Ashtekar: This panel is a little bit different from the last one that we had two weeks ago, this is about future directions, the last one had a single team, this is what has several teams and it was inspired from the.

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Abhay Vasant Ashtekar: The panel that was organized by dog by.

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Abhay Vasant Ashtekar: veteran in the your summer school and it was very successful so we thought we would repeat it here.

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Abhay Vasant Ashtekar: So it's going to be in two parts, the first part is on spin forms and the that will be given by someone and bianca and the second will be on canonical gravity and the talks will be given mythos and add.

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Abhay Vasant Ashtekar: Each speaker has 10 minutes, and then, after two talks will have 10 minutes discussion and after the second two talks will again have 10 minutes discussion, so please similarly go ahead.

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simone: Thank you very much, thank you very much for the invitation to the panel and to everyone for tuning in.

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simone: I would like to as a by said suggest some thoughts tomorrow over the winter break concerning the.

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simone: situation with people's with a quick sketch of the state of the art and some ideas for directions which are building on my own experience, but also on trying to understand what the researcher actually developing in this field.

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simone: And because the time is short, this catch will be very rapid but it's just to remind us that there's been plenty of improvements to the dynamics of spin forms, we now have a vertex that.

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simone: can be used to give up into towards networks it exists in a quantum group version which is related to the cosmological constant.

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simone: there's been an impressive development of numerical methods and these aren't the droids are not just the Games to play with the.

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simone: constructions of the theory that actually been used in a number of applications problem they got to be done propagate or to the study of big rotation.

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simone: occlusion intervention in black also so they are being used as a tool and there's a merging.

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simone: Of the Community with different peoples in devalues nodes that actually contributed and working this, which is also quite important.

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simone: yeah, this is far from being enough to make the formulation really successful, not enough is he had known about the sun me refining and continually meet issues.

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simone: We are still not able to compute the explicitly with many vertices.

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simone: there's the issue of coupling matter form of definitions existence so something that has been investigated by the practical consequences of the company has not been really worked out.

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simone: And also, very importantly, the connection mechanical composition is to be done, more especially, we have the opportunity of doing sort of mini super space models for instance we do something every comment again at the end.

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simone: But the three thoughts I would like to suggest for for mulling over are related we're also we're here about the medical mentors and curvature, and this is the first one and i'm going to comment on.

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simone: So then American progress has been really impressive, as I was pointing out, thanks to the involvement of many, many people.

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simone: From these all the calculations, they were based on degree to propagate or four up the number of green model to what we are able to do today it's really impressive the improvement that there's happened in terms of technique accuracy ideas.

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simone: From the outside, it may look a little bit disappointed, because this was in 2007, and this was one for simplex and existing one for synchronous in 2001 21, and these are three four simply says.

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simone: So, from that point of view, the city lots of work to do, of course, but they will like to point out that the.

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simone: Movement they increasing complexity from going from the Berkeley model today era model is actually very high.

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simone: And so the fact that the medics has been able to catch up with this increasing complexity here, you can see an example.

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simone: From a simple elementary functions to or complicated some of the other functions here so that's very important, and so there has to be can be kept in mind.

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simone: And the extension store values for simplicity is something that is going to these developments.

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simone: More importantly, there's no medical methods have been very useful in that in helping out clarifying one big question that has been around the field for various years, which has to do with the dynamics and I fixed form.

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simone: The probably most known result of bias people more than just the fact that in your genius slope speed limit to the single vertical example to the producers exponential so reggie actual, and this is something that has been considered always to be promising promising classical.

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simone: infective properties extend the consistently to a large form, then we can expect the diagram like this, where it's been four months to do it on a fixed form as a semi classical in the sense of.

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simone: Community me given by some rejection and then they continue the meat of the reggie actually something that is more or less under control and related to general activity so that's how the dynamics could be recovered.

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simone: However, these recent discussions trauma, the situation is a little bit more complicated and that's just it's a large homogeneous well just feeling, thanks in particular to this example of three four simply says is that the three example, but as we started by many people.

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simone: And, at first sight, that in the matrix a simple sure that both flat and current solutions had the critical behavior in these products from the Donna good senior staff on paper.

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simone: But then in fact that these was in contradiction with their fatness arguments of communion ski and bombs on Jonathan angled already there any others.

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simone: And so it was a perplexing for a while, but then better improvement of the medical mantels and pushing the exploration or mega corporation to the limits.

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simone: Especially a suggested by one discussions we had but also many other people participated sure that in the end, actually the curve, the.

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simone: contributions they called the configuration so add the exponentially in agreement with this analytic fatness discussions so effectively there is this discrepancy of of behaviors is a plot also by Francesco would see me but.

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simone: machine and collaborators on one, it also their own version of this product.

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simone: and actually they gave a nice evidence recently another do these exponential suppression is there, it can all you can nonetheless be considered as a critical behavior except that they could even point is complex.

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simone: These analogies allowed them to estimate that the discrepancy between these critical or complex point the end expected reggie behavior the one who have in this situation.

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simone: And what comes out is that the difference grows, both with the messy parameter gamma and with the curvature chosen, so this leads.

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simone: To the suggestion that directed behavior is what approximated he we don't just think that are just feeling it, but we take large PV meet but not infinitely large, we have to still.

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simone: require that the curvature that is generated by the spins, it is not to be.

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simone: So delta here is that the fec dangle in the righteous answer to something that is determined by the spins themselves.

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simone: So not that busy in some sense and sort of normal genius is believing because even though you're thinking, this means large, you may still want to have some of them scaling Melissa saying the same way, so that you can play around with the delta that you produce from these variables here.

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simone: To be fair, arguments like these that you need this morning gamma or small curvature were already made by machine and maybe 2013 and also by Elena Yar incompatibility so.

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simone: it's it's an interesting stronger results are some ideas that have been floating around and, interestingly, more recently, the very same bounder a very similar one has also been attending this effective stream of one model approach.

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simone: presented by a santi bianca an algorithm, so there is growing consensus on the status of flatness, which is quite impressive.

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simone: And we all agree that the core of the reggie geometries don't appear with three ourselves, but this may be sufficient in nearby so that the continuities not spoiling the.

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simone: And not is that qualitative is limited, this behavior here this boundary boundary that behavior here is not too bad because any way for a legal term limit already jumped interesting one, where it's more deputy tangled.

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simone: So, the key question here is whether this qualitative behavior is also quantitatively accurate enough.

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simone: So if you want to, we need more evidence to make sure that these different angle is compatible with Richard when he gets around to dynamics both mentioning collaborators and bianca I have some results in these directions, we need more.

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simone: And then we need to understand whether there are facts or such skating's here in this standard way they continually meet from reggie generativity school.

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simone: Whether the same proof comes through or not, this is something else I would like to see.

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simone: More importantly, the second thought I would like to suggest to mull over over the Christmas break is how do we compete quantum connections, if there are effects like needs to be taken into account because.

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simone: The issue with quantum correction is very complicated, a priori, in asking for more than you have various sources of quantum correction is that will enter.

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simone: Top of the senior classically there's the descriptions of the spectrum, there are standard but integral.

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simone: Like corrections that come from their education and there are also corrections they come from the fact that their behavior is only obtain that the critical point of the alarm integration, then there are also corrections to that.

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simone: And then, our corrections from different forms, so this is a.

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simone: principle, it can be a very complicated structure it's important to have some organizing principle or some quantitative results to know what happens.

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simone: My own experience, take it for what it is because it's just my own experience, it is that in some simple, more than one can do explicit calculations and get these.

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simone: get these organizing principles, for instance in the 3D to be more than one you can compute collection to the garbage on propagator and it turned out.

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simone: That the stream from corrections, namely the departure from the edge of behavior only enter that the next to next to be important.

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simone: So you see, was a quantitative results and is the type of thing that it will be great to have some four dimensions.

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simone: And if there is no disease shown the curvature that can be an important role in this bound on the curvature campaign important or in organizing the.

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simone: Corrections same with the contribution of different forms, my own experiences that in simple systems, it is possible to to see that.

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simone: Increasing the complexity of the form of the contribution to the large spindly meter of a given me to decreases, for instance, you can see in these people cosmology there's a need to decrease in the.

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simone: In the power law in the ingenious last name it and if interesting correlations you can see where the start.

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simone: So very simple model ballistic give you some organization that is completed again if we don't need to dig into account that finance beans North Carolina for curvature it's important to understand how these effects this type of analysis here.

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simone: final thought they wanted to lower which is maybe not a little sense anachronistic because it's a result of from one year ago, when I was more worried about the flatness then now, thanks to these nice result of bianca machine and the collaborators that i've already mentioned.

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simone: Most of these sick question at some point where around the D sharp the specific constraints or whether they were being posed in the maybe not with it was too strong.

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simone: And there's some things that I would like any way to throw out there for thinking is that working at actually emotional simplicity in the semi classic interpretation, even without the simplicity constraint, so that we work this intuitively, let me just catch it so in the repo and modern.

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Abhay Vasant Ashtekar: era little bit over time so maybe.

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simone: Already, so they started okay Oh well, then no worse than the disease in case there are discussions.

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simone: So to summarize, I think we need to continue developing these no medical tools they've been useful already to reach consensus among various researchers and that's something that we need to continue doing.

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simone: any particular these calculations of fixing boundary configurations to look for the semi classical behavior and compare it with a calculus on the one hand.

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simone: But also, on the other hand, computer number two, what do we do quantum gravity affects like the tunneling.

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simone: They can use a search group or after that's also very important, because it offers a comparison know we're educators, in this case, necessarily, but also with the composition of.

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simone: canonical methods of mini super space, so I think these are trying to reproduce the results that can be obtained with other approaches, is a key future direction, now that explicit populations, or at least to some extent possible sorry for going over time.

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Abhay Vasant Ashtekar: No, no you're not over time that's fine.

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simone: Okay, then they can have the time to read my last slide, which is the fact that is effective.

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simone: able to capture key features of the EPL model and provide justifications of the compensation scheme use that they're faster to analyze the medically, so I think there are worthwhile.

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simone: The tool investigated so it's a good moment to leave the table to the anchor to present some of the future views, and these are.

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Abhay Vasant Ashtekar: Great Thank you very much, if there's a very quick clarification that question, we can ask now, if not we'll have 10 minutes after the anchor stop So if you have any questions, please.

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Abhay Vasant Ashtekar: speak up or maybe raise your hands, I can check here if anybody's hand is raised.

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Abhay Vasant Ashtekar: No so bianca you can start sharing.

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Bianca Dittrich: Thanks to.

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Bianca Dittrich: My two GS committee for inviting me and thanks to is mono for this nice introduction.

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Bianca Dittrich: I want to make two points.

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Bianca Dittrich: If I if I manage and that will be to concentrate on universal features and so first is kind of universal features of certain forms.

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Bianca Dittrich: So what we have in lukewarm levity and it's informed, I said areas emergence more fundamental degrees of freedom and have a discrete spectrum.

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Bianca Dittrich: And that's quite different for matrix a purchase but it's also converting this many other coaches community based on on some dynamics entanglement Obama degrees of freedom.

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Bianca Dittrich: So an interesting consequence of that.

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Bianca Dittrich: is actually which which discovered this actually that, since they are to be much more alias and links, you do not only have matrix degrees of freedom but additional torsion degrees of freedom.

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Bianca Dittrich: And also, you said needs to be unnecessarily an anomaly in the hall from primary simplicity constraint or equivalent D inside of of secondary simplicity constraints and actually that's parameters, what about using quantum.

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Bianca Dittrich: So actually there's a big opportunity because that means that these additional degrees of freedom which.

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Bianca Dittrich: Due to the anomaly cannot be suppressed exactly or funny quote have phenomenal logical implications and fact one of these implications is actually the flatness problem.

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Bianca Dittrich: So one control that applies to all methods, they are you have areas of independent variables and you have enough approximately equal distance spectrum, so if he believes that these are the right fundamental degrees of freedom, we need to indeed figure out how to solve the flatness problem.

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Bianca Dittrich: And, as someone mentioned and get the most explicit America poof now, so this force and the.

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Bianca Dittrich: EPA and mana, but you can also consider simpler model which captures is key effects and then i'm not going to explain it affect us and for models.

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Bianca Dittrich: But just to advertise it basically you need just seconds on the laptop instead of weeks on high performance computers and an Office also more transparent and pulling off the dynamics in particular of office constraints.

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Bianca Dittrich: And so, actually in the district case.

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Bianca Dittrich: This head of these models he provided the first two sets of education of motions are equals point examples in the edge.

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Bianca Dittrich: And their display computing really the full number two which partition function and expectation millions of ultimate so that hasn't been done any other.

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Bianca Dittrich: context, so it requires a smaller but the only music parameter, but it actually allows for large deficit england's fossil.

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Bianca Dittrich: spins report will consist it's completely consistent with academics and the stitching it's also completely consistent with semi classical resides on you get the same bound and you get also complex data points, and in fact I believe that you could compute.

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Bianca Dittrich: Something like an effective than four models by starting on vpn by integrating our just a seamless.

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Bianca Dittrich: way so much about the discrete Simone also mentioned this issue, what happens in the continuum limit actually in the continuum limit there's a very surprising design.

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Bianca Dittrich: We chose that we actually never needed to really worry about the FLEX constrained, and so the flatness problem is particular doesn't if you just take the every rejection.

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Bianca Dittrich: And so, if you take the area of education and expanded on a hyper to read the letters and integrate out all these additional music, which are not submitted to them what you get is actually.

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Bianca Dittrich: The interesting here, but action.

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Bianca Dittrich: We do data collection, which is of force on and the lattice constant so in the continuum limit a good kind of vanished very fastly and forward into a chance on.

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Bianca Dittrich: So even if you do not impose upon Spain so dynamics of the resurrection.

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Bianca Dittrich: suppress SES SES degrees of freedom, and that is also flexible.

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Bianca Dittrich: And so the actually is a mechanism here is that all these non metric is a feed them are getting very massive and the continuum limit.

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Bianca Dittrich: And so that's a mechanism which is likely to extend and to also help and higher order evolutions and if you do add constraints, the only change is to add to the mass, which is already there basically a DEMO dependent.

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Bianca Dittrich: Come.

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Bianca Dittrich: So I see different spin for mothers basically asked just different versions of how these normative discipline muscle test all these some physical things on post.

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Bianca Dittrich: But in this continuum limit these degrees of freedoms, our enemy success, so this, we have an emergence of universality again into continuum limit of getting to the ancient inhibit action that's connections.

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Bianca Dittrich: So what would be nice to have is in fact an effective continuing action for certain forms which comes from including distortion degrees of freedom and this, this would give us one day of physically dharma induced production to the permutation of dynamics.

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Bianca Dittrich: In the continuum limit.

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Bianca Dittrich: So that finishes my first universe university point, the other is to actually concentrate on universal features for quantum energy and particular to emphasize that informs on one of the few approaches, based on the new invention or here time possible.

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Bianca Dittrich: However, it's actually we haven't really reached, at least in America and visit visit you can edit key.

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Bianca Dittrich: Models the problems, maybe populism events and passengers and issues which are difficult to test this is causing delays and that's basically if you encounter integrations of what infinite loop.

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Bianca Dittrich: So it is a question, how do we actually compute pass into this file oscillating on people's and practically unbounded integration age.

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Bianca Dittrich: What happens with a conforming factor program of kidding quantum gravity, which actually kid almost all letters a purchase and which comes from this unbounded integration range.

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Bianca Dittrich: cleaning and these issues will be key to understand the amount of it from kingdom limit.

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Bianca Dittrich: and related to the length and content IGLOO is actually what constellations to some over should we allow for causally irregular configurations are not as these are related to topology change and time should we, what should we do this or team configurations of Uzi appeal the marketing.

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Bianca Dittrich: arm so here are some answers to these questions, there is the first one actually in the recent years there have been some methods.

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Bianca Dittrich: developed which are related to pick our lifshitz methods basically it's a prescription how to deform you integration domain and the complex plane, and it has been used and various examples already.

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Bianca Dittrich: And effect where we have thought it already is something cosmology examples, and that makes integrates quickly convergent.

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Bianca Dittrich: And also you do get in, for instance arcadian or contributions, even if you start forms inventing site.

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Bianca Dittrich: But it also shows that you can allow for causally configurations, but these will be likely suppressed, that is the kind of to convergence with other.

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Bianca Dittrich: reporters you live is closer than any final decisions in the sense that causes unlimited simulations explicitly forbid is positive, either configurations.

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Bianca Dittrich: That might not be the case and that might not be needed in our case, but they ultimately suppressed by the dynamics and so we again have something similar in common, this call to the negative emotions.

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Bianca Dittrich: Also very few designs and cosmology based on the collections methods, and so we also can vouch.

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Bianca Dittrich: For.

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Bianca Dittrich: Similar resides this is continuing integrations.

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Bianca Dittrich: And there's actually a lot left to explore for events in passing dividends.

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Bianca Dittrich: And for that we need in fact of number allocation models and methods and actually.

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Bianca Dittrich: they're the easiest context and to cope see since I actually cosmology example switch will lead to poor people.

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Bianca Dittrich: So to summarize.

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Bianca Dittrich: We should concentrate on university features of smartphones and also my view of it's best to use kind of the simplest or the model which is most amenable to numerical methods.

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Bianca Dittrich: And, in particular since sampling foods of any model change i'm opposed training flow and the universal features, with a wife.

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Bianca Dittrich: And on the other hand, we should also put more effort into.

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Bianca Dittrich: investigating universal features of quantum gravity.

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Bianca Dittrich: For instance, actually making really use or is it via one of the few reporters the East on the lenten possible Thank you.

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Abhay Vasant Ashtekar: Thank you very much bianca and thank you both of you for such nice and succinct summary so where time for discussion, and I think he had raised some question before, and then there are there are some other questions Lee.

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Lee Smolin: Go ahead, yes, thank you, that was a beautiful summer again.

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Lee Smolin: This is going to be simple mind interactive just for fun, if we go back a long time to the thinking people who first started about three miles upon various times.

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Lee Smolin: They were relying on intuition from ordering cornfield series coming from how they called me Dr Wilson, and so forth now intuition.

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Lee Smolin: said that master's degrees of freedom dominating the infrared and if you can accidentally make other degrees of freedom by losing symmetries.

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Lee Smolin: You, they will be very massive another another class now, so the idea that we have viral origin like degrees of freedom hanging around the planet scale we go below that we see masters in two fields it generally.

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Lee Smolin: is not surprising describe it it's a wonderful thing to have is confirm these methods pituitary is what we really expected on.

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Bianca Dittrich: Your.

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Bianca Dittrich: passion, without surprising or not.

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Bianca Dittrich: yeah I mean, I do think it would be good to connect to this literature and.

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Bianca Dittrich: have an.

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Bianca Dittrich: associate.

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Bianca Dittrich: kind of the continuum version of suspend form effective action.

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Lee Smolin: I think that will be useful to know I mean you're seeing and very good careful calculations effects that we expect to be there and I think that's because enough immensely important news.

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Bianca Dittrich: So you mean that.

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Lee Smolin: These have been reason why there's.

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newer.

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Lee Smolin: newer calculations is better.

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Bianca Dittrich: So.

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Lee Smolin: The reason why the newer calculations better, but the intuition that you're confirming is this very old.

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Bianca Dittrich: yeah so i'm assuming visit.

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Bianca Dittrich: yeah Lee i'm confronting this intuition, nevertheless, you had also took place in one of the pitch which.

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Bianca Dittrich: Was the running water, simplicity things.

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simone: So i'm into but even Steve with this don't don't we need further evidence before we can, because you said that these degree of freedom dicaprio but you were looking at the free action, the quadratic action.

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simone: No don't We further evidence that they don't spoil the interaction of the law and so.

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simone: I think.

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Bianca Dittrich: yeah see effects, as I said that.

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Bianca Dittrich: The degrees of freedom are getting very methods so it's basically as a mechanism indeed set as you mentioned, you will have.

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Bianca Dittrich: below a certain cutoff given wise as mass these degrees of freedom they're not be excited.

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Lee Smolin: Right.

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Bianca Dittrich: So, even in the directions so that's what I meant that it provides also mechanism which can help you for for nonlinear order.

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Lee Smolin: Yes, yes, I think.

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Bianca Dittrich: So so.

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Bianca Dittrich: Everyone so of course it's it's important to to to do more calculations and us as we have done, we have done it for an edge and effect where we wanted to come more complex simulations but that the violence, the things I mentioned that the connections message was a moment.

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Lee Smolin: So that eventually but we didn't have that many years ago.

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Bianca Dittrich: And, and you know, and that is actually something that you air force and he but independently of that is kind of you need also to to learn how to compute prevention's.

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Bianca Dittrich: Possibly girls and it's not only our Community, but it's a subject in many areas of physics, how do you compute civil went in passing people it's effective.

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sure.

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Abhay Vasant Ashtekar: Of course, it becomes more serious and called gravity.

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and other gases.

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Bianca Dittrich: For quantum gravity indeed you know if he can explain how, how do we escape I mean, obviously we don't have to confirm effectual comments, but if he can pin down.

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Bianca Dittrich: status sets what happens is to confirm effectual when we could be much schumer about suitable continuum limit.

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Bianca Dittrich: And conformal factor column is basically related to in some sense, in fact, that you UV mixing one format divergences can see to the problem of Spikes and also getting always a problem your face so that's kind of an important issue in general to explore.

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Abhay Vasant Ashtekar: yeah I kind of feel that, although that there was intuition, as he says, I mean.

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Abhay Vasant Ashtekar: When when tried to do it in detail, it appeared that there were also serious problems, but just flatness problem of issues with simplicity.

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Abhay Vasant Ashtekar: And therefore, having these results concrete results is is extremely extremely helpful ID and also, I feel that, having this effect to action, which is a future thing that bianca pointed out, would be very good, because that will tell us you know what are the.

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Abhay Vasant Ashtekar: kind of quintessential corrections coming from quantum geometry right because they will tell us relate to you mercy back, so I think that would be extremely useful Okay, I think we should go to the next question which was Alejandro is an android you're still we are questions.

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Alejandro Perez: yeah yeah I am here I just had a very simple question I wanted to know well, thanks for both presentations were very nice, I have a question for bianca.

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Alejandro Perez: So, when you say these things are this spurious news, they are sports degrees of freedom that are massive that become very massive in the Canadian limit.

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Alejandro Perez: Is this a way of speaking, or I mean is there, what is is the precise definition of what their mass is, how is it that you or is it that the artist suppressed in.

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Bianca Dittrich: In some so in in the calculation on a hypothetical letters.

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Bianca Dittrich: You know what happens is that said it's it's kind of hard so I mean a non trivial thing that you can that you do get terms with the riveters.

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Bianca Dittrich: And, and that in principle requires some fine tuning, that is, I mean it does.

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Bianca Dittrich: It I mean a random action would not have my master's degrees of freedom, but the action we start with typically direct action has his master's degrees of freedom, so the actual problem is actually to define a disposition, so that you really get your master's degrees of freedom and.

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Bianca Dittrich: If you do not get it a little bit of that means you have a mega milestone, and so, in that case, typically the milestone is just living in terms of the lattice constant in that case, but I am since its force Odin the lattice constant.

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Bianca Dittrich: You can figure out what's a master years it was kind of somewhat automatically in the lattice constant automatically in the inverse of the next constant.

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Bianca Dittrich: yeah.

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Bianca Dittrich: I don't know if that helps but it's clearly.

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Abhay Vasant Ashtekar: So basically dancer was that.

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Abhay Vasant Ashtekar: The question was What do you mean my mastermind you're saying that by master human terms, which do not have derivatives is that produce.

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Bianca Dittrich: yeah yeah so yeah.

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Abhay Vasant Ashtekar: Does that answer the question.

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Alejandro Perez: Yes, kind of yeah and they are and they are, they have no derivatives and they are quadratic in some sense because they could be interactions right right.

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Abhay Vasant Ashtekar: And contracts.

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simone: Well they're only looking at the Arctic.

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Alejandro Perez: The only looking.

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Bianca Dittrich: At Lynn is the masa masa point is not part of it.

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Bianca Dittrich: And the latest kwanzaa in those letters constant.

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Alejandro Perez: And one is linear racing around.

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Alejandro Perez: What.

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Bianca Dittrich: plot this case let's face.

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Alejandro Perez: Defining this cubic ludus.

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Bianca Dittrich: This hyper cubic meters.

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Okay.

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Alejandro Perez: Okay, thank you.

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Abhay Vasant Ashtekar: Okay, any other question.

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Lee Smolin: Can I just quickly go back to the point that's the whole point of hola Nielsen institution good is it random theories, to have mass this mode.

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Bianca Dittrich: Okay.

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Abhay Vasant Ashtekar: Okay, so I got a couple quick questions I hope the first is that.

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Abhay Vasant Ashtekar: The result that you had with the.

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Abhay Vasant Ashtekar: With the.

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Abhay Vasant Ashtekar: That you needed this gamma to be you just said that gamma is to be less than point 0.1 so what happens if I just met gamma to be what we believe it to be with respect to you know black hole or cosmology calculation and make it just Point two 4.25 what happens.

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Bianca Dittrich: That depends.

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Bianca Dittrich: It depends on on what kind of curvature scale and what kind of.

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Bianca Dittrich: Practice, so they will recover that case, but it does have coverage is much smaller or what is the state.

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Bianca Dittrich: That here, you see here, you see an example what's the population which be done for range of comma.

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Bianca Dittrich: Zero point from from zero to the roughly 7.7 or something and and So you see, you see it's a bit hard to predict, because what happens for larger gamma you see that instabilities occur.

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Bianca Dittrich: and

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Bianca Dittrich: This comes from highly kind of.

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Bianca Dittrich: unknown parameters effects and, since that.

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Abhay Vasant Ashtekar: That is that gamma is like.

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Abhay Vasant Ashtekar: 1.5 or something like that point 4.5.

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Bianca Dittrich: yeah yeah.

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Bianca Dittrich: yeah.

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Abhay Vasant Ashtekar: yeah so what I was, I was talking about what you know just as a or coherence which has.

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Abhay Vasant Ashtekar: To do with just just bigger than point 2.24 or something, are you there, yes.

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Bianca Dittrich: Yes, these are extremely small Indeed, these are extremely small fluctuations so, and here it happens said, this is indeed still goes to 0.4 as a deficit being English is quite large actually.

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Bianca Dittrich: So, in general, you will be it works, the better as small as a difference in English and, in fact, if you look at smoother examples which you have for just a few if you just use one tyner.

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Bianca Dittrich: The pictures I don't have this picture to picture will be a bit smoother, but the question is, do you us having just one time and see six months we mentioned the skis increases in that case you get quite small to the flat limit, indeed, a few, if you do make them bigger and bigger.

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Bianca Dittrich: You go back to the to the to the flat.

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simone: You need to stop a smaller speeds in order to suppress the curvature is.

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simone: A stationary.

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Abhay Vasant Ashtekar: Mostly okay.

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Bianca Dittrich: yeah so, but at least a report of the expectation of schools.

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simone: And then the question is whether such as motorists beans, with the flat good the deficit angle still be governed by the reggie solution is that relevant and bianca linear models has shown, yes, so far, but I think we need more evidence for that.

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Abhay Vasant Ashtekar: Okay, the second thing was that we also some you know, we do expect that.

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Abhay Vasant Ashtekar: There was some higher curvature corrections to the effect to action.

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Abhay Vasant Ashtekar: At the moment, you're saying that these are all supposed to you know, but for GA lattice fake spacing.

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Abhay Vasant Ashtekar: So what what is that telling us in terms of the curve, you know, in terms of curvature is it is, it is it telling us that.

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Bianca Dittrich: hey this these connections are only coming from the effect of having additional degrees of freedom.

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Abhay Vasant Ashtekar: Okay, yes, but maybe related to higher coverage in terms of the action.

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Bianca Dittrich: yeah so and you get something for the Arctic and the curvature.

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Bianca Dittrich: But what I mean so linear term seems not up yet.

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Abhay Vasant Ashtekar: that's what you're saying.

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Abhay Vasant Ashtekar: Because its fourth order, as opposed to second order.

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Bianca Dittrich: Something.

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Abhay Vasant Ashtekar: Up to do, which is linear in curvature like like like the.

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Abhay Vasant Ashtekar: Does the scale of curvature, for example, like.

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Abhay Vasant Ashtekar: started minsky model.

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Abhay Vasant Ashtekar: Is not appearing is that what you're saying.

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Bianca Dittrich: you're not in this not in this calculation.

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Abhay Vasant Ashtekar: I think is an important point is conceptually.

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Abhay Vasant Ashtekar: Do don't like urbanski action is not.

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Abhay Vasant Ashtekar: appear in this calculation.

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Abhay Vasant Ashtekar: up, yes, it seems to be quadratic encourage.

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Bianca Dittrich: What what what I want to emphasize and in a similar mentoring different kinds of production, so this comes only from these additional degrees of freedom.

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Bianca Dittrich: But it's not taking into account the descriptions of the spectrum.

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Bianca Dittrich: yeah.

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simone: Well, this seems to be though Maybe she can comment further, but the in depth analysis.

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simone: If I understood it correctly, they have a correction that is squared in the deficit angle, which one we think it's like stravinsky like, of course, the problem is that you can you don't know if it's fake which is killer square or which tends to square because of the disk utilization.

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simone: But it looked like the day started at.

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simone: A quadratic or not.

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Abhay Vasant Ashtekar: At least know what i'm talking about richie scale versus it just kill a square.

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simone: Exactly yes.

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Bianca Dittrich: Yes, yeah.

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Bianca Dittrich: So this is, I think we will.

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Abhay Vasant Ashtekar: Continue again at the end of the whole discussion period because we should go to the second part, which is get on the calendar, a little bit behind schedule.

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Abhay Vasant Ashtekar: as well.

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Alejandro Perez: Can I say something very shortly about it.

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Alejandro Perez: So, so this mass I mean, I agree with the comments of me and it's very interesting that younger you find this thing so so it wouldn't be strange to imagine that this I mean the masses here in your model they blow up in the limit a go into zero I suppose.

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Bianca Dittrich: it's not going to you know know who is an artist once in a.

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Alejandro Perez: While yeah sorry response, but in the physical theory that they will be naturally blank mass.

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Bianca Dittrich: I see us going out so indeed you can assume that this is kind of 100 plant managers and, depending on what you consider.

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Alejandro Perez: What i'm saying is that this could have important phenomenal logical consequences, I mean it's.

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Alejandro Perez: Natural to expect having plant massive stuff in in theory.

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Bianca Dittrich: yeah so so.

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Alejandro Perez: Our Center seems I mean we are people everybody's looking for dark matter in you know, in the standard model and.

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Abhay Vasant Ashtekar: I think we are going a little bit too too much now just point here, which is a lot is the last question, which has to do with the you just asked that can speak us.

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Abhay Vasant Ashtekar: say clearly, if there is a consensus on the flatness problem and if there's consensus, what is it, this is the last thing and then we should go to the next part.

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Bianca Dittrich: Right, it simply says consensus that we make big progress and resolving this and there's a bit of this agreement to which degree with results.

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Abhay Vasant Ashtekar: Okay.

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Laurent Freidel: let's go to the mixtape will be the what was the problem and the resolution because finance specialist I think it's not I.

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simone: Thought i'd done these during my talk.

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yeah.

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simone: page seven and eight.

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simone: Well, the growing consensus, even though it's not universal is that there is evidence that one we get a behavior that is.

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simone: Complex critical and close enough to the reggie behavior event for curb the solutions and maybe this is enough to recover the continuum.

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simone: There are mechanisms that are being produced so there's agreement that the results are those don't exist for current solutions, but there may be some things that are close enough so close that they don't spoil in the continually me where does he seem to be.

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Bianca Dittrich: Because.

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Abhay Vasant Ashtekar: i'm not the one should go back, I mean, because then we can come back and ask questions to all the speakers so let's go to the second part, which is through the canonical one and Thomas can you start sharing screen your yeah.

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Thomas Thiemann: Just a second now.

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simone: he's trying to finish the slides probably.

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Not.

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Thomas Thiemann: Can you see this.

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Abhay Vasant Ashtekar: Yes, thank you, excellent okay.

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Thomas Thiemann: So thank you for first of all to the organizers for the invitation to speak here um, so I will be focusing on the canonical approach, and more specifically.

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Thomas Thiemann: The foundations of the canonical approach, more to the applications will be covered in talk by ED and even more specific, I will focus on what I think is are the key questions.

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Thomas Thiemann: um.

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Thomas Thiemann: So.

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Thomas Thiemann: Yes, my one slide of the definition, what we want.

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Thomas Thiemann: fury of quantum gravity to quantum gravity to be so for me quantum gravity is quantum few methods apply to general relativity that includes geometry and matter.

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Thomas Thiemann: um it's a quantum field theory of a new kind in the sense that it's defined on the differential manifold and not on the background space time because the space time itself as being contrast it's a continuous up and not the descriptors theory and it's for physical or instant signature.

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Thomas Thiemann: it's a fundamental theory and not some effective quantum v3 and, therefore, necessary and non productive and technically what are.

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Thomas Thiemann: What is the task, the task is to find an representation of the canonical computation want to computation relations, such that the operators that drive the dynamics are densely represented in this space.

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Thomas Thiemann: i'm.

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Thomas Thiemann: The few we should reduce to quantify three enclosed space time, which is very established when the fluctuations about the metric that you want to approximate are very small, and it should repair the inconsistencies of classical relativity so prepare the classical singularities.

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Thomas Thiemann: What is look quantum gravity is an attempt at the concrete and mathematically rigorous implementation of that program the tools are very conservative is just aren't engaged three variables that are familiar from let's.

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Thomas Thiemann: CD to define the commutation or anti commutation relations and then just represent representation to you, we have operators.

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Thomas Thiemann: In contrast to let's quantum quantum lettuce curiosity you're working here with a continuum theory units to back on independent representation harder than the more familiar fork representations.

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Thomas Thiemann: So what is the status of the new quantum gravity or quantum gravity, in more general terms.

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Thomas Thiemann: Or, more specifically what us, what are the differences between porter with an alternative approaches.

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Thomas Thiemann: Let us remind us, what is the basic problem of one of the most serious problems of the photographer portions that leads to three problems.

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Thomas Thiemann: First of all, they are an infinite number of ultra violet divergences um and the two processes it's a photography theory there's a total today's interview series to be sent over which is likely to have zero radius of convergence.

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Thomas Thiemann: And there are, as far as we can tell them, we are no miracles cancellations infinitum of contact Tom says mute therefore The theory is not predictive.

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Thomas Thiemann: In energy, you have the hamiltonian constraint, as the as the as the thing that drives the dynamics and here you see that are there are there's a lack of the verses.

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Thomas Thiemann: there's no serious to be some over because it's a non productive approach, however, there quantization ambiguity, so there are.

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Thomas Thiemann: As teams an infinite number of mathematically consistent solutions, and therefore the theory is also not predict this at this point so that's the main message they are promising improvements, but the dynamics is not yet and final shape.

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Thomas Thiemann: And let me go a little bit into more details, what is the problem, and what are the current solution status strategies to solve this problem, the technical problem is that.

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Thomas Thiemann: The quantum algebra of constraints hamiltonian constraints and special different makan can sense it closes However it closes with the wrong structure Constance.

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Thomas Thiemann: So classical classical you have structure Constance which are labeled as a few in the quantum case you have.

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Thomas Thiemann: quantum structure Constance which are labeled G here, and you find that F is not equal to God that's the first problem The second problem is that are.

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Thomas Thiemann: Unfortunately, this.

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Thomas Thiemann: As as usual in quantum theory when you when you want is non trivial operators, you have to realize them this has to be done here in a different.

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Thomas Thiemann: way and, unfortunately, the regulation scheme remember something about the way you did this, even after you move the regulator.

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Thomas Thiemann: So what are the current solution tracks are the two main branches and one of them I phrase as avoiding the quantum constraints whatsoever, by going by a reduced face face quantization path using much you're referencing systems.

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Thomas Thiemann: So you solve the constraints classically and then you don't have to worry about them in the quantum theory anymore.

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Thomas Thiemann: The second branch is to correct the structure Constance and here we have mainly two branches, one I called, and this was initiated by Milan lata and tomlin and it goes, I would say it.

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Thomas Thiemann: Or let me phrase it as this on it, it shows it this relation between the hamiltonian constraint.

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Thomas Thiemann: And the different often constraint, when you admit that, on the vector field of the different offices constraint itself becomes on tight, so I call this a quantum backfield quantization.

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Thomas Thiemann: Of the hamiltonian constraint gets much more to say about this, but let me in this brief talk, let me just put it like this.

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Thomas Thiemann: And the second approach is to use also Roman very normalization techniques in the hamiltonian language.

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Thomas Thiemann: And, since this is a talk about future directions, so the here, if you look for something to do it, and this one my mind one slide that list the main major problems in these three approaches.

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Thomas Thiemann: In the reduced face face quantization there are some principles.

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Thomas Thiemann: That this works with scale a reference fields, more specifically address fields, but the question is, of course, whether these foods are in immunology realistic, and so we have to probably go to a more realistic matter and for him to medical fields.

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Thomas Thiemann: In the quantum battlefield approach, and they are very promising on vacations and results that show that it works quite well in in models, such as.

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Thomas Thiemann: parameters few three and the you want to truncation of Euclidean welcome to our, but of course there's the main question is whether this can be extended to Meta cosmological constant and learns and signature.

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Thomas Thiemann: And then the.

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Thomas Thiemann: Sorry, in the.

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Thomas Thiemann: randomization track so by by design this tries to avoid the.

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Thomas Thiemann: ambiguity, but of course there's no guarantee that it also avoids anomalies, so this all of this has to be studied much more and it's already my my last slides or me just summarize and our want to some recent results.

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Thomas Thiemann: So to turn to quantum Gardena come into a common the accepted and predict, if you really.

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Thomas Thiemann: need to settle the quantum dynamics and here are four examples, why this is a highly highly topical for the whole Community.

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Thomas Thiemann: So, first of all is the details, how the analysis implemented may have phenomenal logical relevance, as has been shown in the connection between Luke quantum data into quantum cosmology and recent works.

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Thomas Thiemann: And then there's the outstanding are not yet settled connection between canonical and co variant approaches as informed approach that was.

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Thomas Thiemann: The topic of the first two talks um so our spin format towards really the rigging map in our products between solutions of the quantum Einstein equations, and this may go beyond just implementing the correct version of the simplicity concerns it goes even deeper in some sense.

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Thomas Thiemann: into the question whether we are actually quantization to the correct measure.

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Thomas Thiemann: has been pointed out in our work for a long time ago by moving to La and others.

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Thomas Thiemann: that's a few results and disrespects that are promising for example doesn't just work that has access to quantum cosmology and, more recently, they are recent current state techniques that.

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Thomas Thiemann: were already mentioned before um.

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Thomas Thiemann: and ask the question.

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Thomas Thiemann: How do we make, how do we take the semi classical limit and can we make contact with concretely in groups based on also wish there would be more precise, but so forth, many works in the context of quantum cosmology and perturbations around it.

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Thomas Thiemann: And last but not least, i'm mentioning this work that just came out last week ago, so let me just explain this result for and in this Nice that listen listening today.

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Thomas Thiemann: You raise the questions whether it is not a generic feature of all these hamiltonian constraints that they are not know our long range correlations in the solutions of quantum Einstein equations due to the action of the hamiltonian consent being much to local.

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Thomas Thiemann: And in this recent work we short that our at least he gave strong indications and that can talk.

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Thomas Thiemann: More about what are these indications restrictions that i'm mentioning here that there is existence of an infinite infinite dimensional corner of.

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Thomas Thiemann: The constraint that even the existence was not clear, so far, which are not normalized but with respect to the different offers an inner investment in our product which is a good thing, because.

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Thomas Thiemann: You do not expect solutions to the are hamiltonian constrained to live in the hilbert space of solutions to their special different dolphins, content and this dude display propagation.

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Thomas Thiemann: and

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Thomas Thiemann: As was mentioned before, it is important to go into details, all of this works involve tedious and complex calculations and encourage much more the use of modern computational techniques such as machine learning and quantum computation techniques, thank you very much for your attention.

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Abhay Vasant Ashtekar: Thank you very much, Thomas there is there is a quick clarification question let's ask Thomas if not we'll go to the last stop.

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Abhay Vasant Ashtekar: The Please go ahead.

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Lee Smolin: Yes, I wanted to mention why I am hopeful about these issues, and this is because of the future that is often mentioned in the covariance inform approach, but not so much.

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Lee Smolin: And if an analytical approach, which is that we have the theory which is cubic where the action is cubic in the basic fields.

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Lee Smolin: Which means the final questions emotional quadratic and we should have an easier time bringing arising and normalizing them and with respect, and this is connected to your last comment about machine learning and so forth.

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Lee Smolin: is very interesting work, I hope I can talk about soon connecting these ideas to cubic general cubic models of thinking.

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Lee Smolin: If you morphing.

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Abhay Vasant Ashtekar: Alright, so thank you Lee let's go to the next talk and then we'll come back to discussion on both Thomas and edge ED can you share your.

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Abhay Vasant Ashtekar: screen and slide please.

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Edward Wilson-Ewing: Okay, can you see that yeah alright, so thank you very much for giving me the opportunity to present a few thoughts about some directions that I think could be interesting for future work.

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Edward Wilson-Ewing: um so just to give a starting point to make sure, on the same page, I think we all agree that the ultimate goal of any physical theory is to describe nature, or at least some part of it.

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Edward Wilson-Ewing: And from the perspective of quantum gravity, this means, I think that we'd like to understand the role of quantum mechanics of space time physics.

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Edward Wilson-Ewing: also understand the microscopic structure of space time and some specific applications so understand the physics, of the early universe and physics and black holes.

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Edward Wilson-Ewing: And, of course, within the context of El que je there are many important problems and we've heard about several those nearly are talks so here, I want to focus on those that are related to applications and cosmology and black holes.

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Edward Wilson-Ewing: So of course we want to study cosmology and black holes both to make contact with observations and to see if the theory that we have is correct and whether we can use it to describe nature and also.

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Edward Wilson-Ewing: Because it can offer some partial guidance for theory development so as Thomas was explaining there are lots of ambiguities in conical framework.

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Edward Wilson-Ewing: and also in sinful models and greenfield theory and by looking at these simpler.

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Edward Wilson-Ewing: physically motivated applications often it's easier to check to see whether we've been able to capture the correct physics or not.

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Edward Wilson-Ewing: And there's been a lot of work both on cosmology and black holes that's been very fruitful.

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Edward Wilson-Ewing: Here I don't really want to go into that so much, so I want to focus on future directions, so what i'll do is i'll just point out some directions, I think, are especially important promising.

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Edward Wilson-Ewing: These are often directions, where there has been some research, but I think there is still a lot more to be done to really be able to answer all of these questions.

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Edward Wilson-Ewing: So one of the important next steps, I think, is to really better understand the relation between Luke quantum cosmology and one gravity so.

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Edward Wilson-Ewing: In my opinion, quantum cosmology has been extremely successful.

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Edward Wilson-Ewing: But it is somewhat limited by the fact that its construction is motivated by one gravity.

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Edward Wilson-Ewing: But it hasn't been derived from one gravity so even though we're trying to mimic quantum gravity when constructing on cosmology it's not clear if we can derive from it.

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Edward Wilson-Ewing: And so, this naturally gives us the question of can we extract the cosmological sector of the punk gravity, so we start from full on gravity, can we figure out what states in that delivery space correspond to cosmology and is this give loop on cosmology at least approximately.

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Edward Wilson-Ewing: And then there are some technical questions so is this perhaps easier to do in a particular framework, whether its political upon gravity or spin phones or group field theory so there's been worth exploring all these possibilities.

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Edward Wilson-Ewing: And I think the real Nice, we could do it in all of them, but perhaps it's easiest in one and, finally, if you think in terms of spin networks.

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Edward Wilson-Ewing: Do cosmological states and full of gravity still correspond to a graph with many small volume nodes with the dynamical number of nodes or dynamical graph or do we have a fixed graph but only a few nodes and the volume of each of these nodes is dynamical.

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Edward Wilson-Ewing: Or is it some mix.

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Edward Wilson-Ewing: Or maybe this question is misleading and perhaps we should use a different representation, so I think these are questions that would be nice to be able to to answer in detail.

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Edward Wilson-Ewing: Another point that I think is important to to think about is a translation problem and cosmology so if we have an expanding universe like when we live in, you have your perturbations.

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Edward Wilson-Ewing: cosmological perturbations which are being read shifted by the expansion of the universe.

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Edward Wilson-Ewing: And so, if you look at a long way, like boat today who's wavelength as much greater than the Planck length, if you track it back now usually.

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Edward Wilson-Ewing: back in time to when the universe was much smaller you'll find that had a shorter wavelength, and some of these modes that appear to be long wavelength today would have initiative in translation.

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Edward Wilson-Ewing: So they would have had the wavelength shorter than the Planck length again, this is just if you track it natively backwards in time so.

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Edward Wilson-Ewing: The question that we should answer and on gravitas whether these translating those exist or not.

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Edward Wilson-Ewing: If they do exist, presumably these very short wavelength modes will have some modifications their dynamics due to quantum gravity affects.

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Edward Wilson-Ewing: And is there no playing still cut off whatsoever can we really go down to arbitrarily shortly once or.

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Edward Wilson-Ewing: Is there some cough somewhere and then, if there is where and how does that happen so if there is a cut off then presumably as universe expands, we have some new modes that are created an expanding universe, and then this can raise all kinds of problems with unitary so again, this is.

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Edward Wilson-Ewing: A problem in cosmology I think we have to address.

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Edward Wilson-Ewing: and try to understand what the quantum gravity has to say about these points.

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Edward Wilson-Ewing: Okay, so those were two topics and cosmology Of course there are many others just due to lack of time I just picked a few that I personally wanted to focus on.

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Edward Wilson-Ewing: So let me move on to talk about black holes.

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Edward Wilson-Ewing: I think you know it's well known that the lifetime of black hole is complex enough fully understood and we often talk about problems about the late stages of the life of a black hole.

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Edward Wilson-Ewing: So talking about hawking evaporation information last problem, but I think it's also worth keeping in mind that quantum gravity is presumably important very early also because.

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Edward Wilson-Ewing: The singularity forums very soon after collapse, so, if you look at any sort of collapse model.

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Edward Wilson-Ewing: you'll find that the singularity forum is very, very rapidly and so presumably quantum gravity affects will be important quite rapidly also it's not only.

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Edward Wilson-Ewing: about the late stages, it is that, but also about the early stages of the lifetime of black hole so can we track the evolution of a quantum black hole from its formation to its eventual disappearance.

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Edward Wilson-Ewing: And there are a few key points here, the first is that I think it's very important to include matter, so I think.

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Edward Wilson-Ewing: there's some intuition from classical GR that's a little bit misleading for us, because of course in classical GR if you have some matter inside the horizon.

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Edward Wilson-Ewing: Then that matter will eventually land on the singularity and then we don't have to worry about it, or we can just worry about the vacuum solution.

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Edward Wilson-Ewing: But if quantum gravity removes the singularity then that matter is not going to go away and we should be able to include it in our description understand what happens to it.

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Edward Wilson-Ewing: Since we're talking about quantum gravity, we would expect that the singularity will be avoided.

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Edward Wilson-Ewing: and probably the space time will be extended beyond where the singularity was so how exactly is the sealer avoided.

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Edward Wilson-Ewing: Is this space time extended If yes, how is extended, these are all questions that we should try to answer and another point is that there have been some arguments in the literature recently that young and black start, young and old black holes are different.

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Edward Wilson-Ewing: So I say you say you take a map of life of a certain massive so young Black Forest old black hole it'd be very different.

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Edward Wilson-Ewing: in part due dates entanglement with hawking radiation, but is there anything beyond that, so if you have a young and old black hole just how different are they.

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Edward Wilson-Ewing: And finally, of course, say I to attack the information last problem we have to be able to track where the information goes there'll be some transfer from geometry to matter, perhaps back again and perhaps this information will.

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Edward Wilson-Ewing: will be transferred between geometry matter in different ways at different times and we would expect that it won't be lost, but it would be nice to be able to see exactly how it's preserved and how it could, at least in principle, be recovered afterwards.

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Edward Wilson-Ewing: Okay um and, finally, this from my last slide I want to just mention something that's very ambitious.

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Edward Wilson-Ewing: So far, most of the work on black holes has been looking spherical symmetry, of course, this makes calculations, a lot simpler.

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Edward Wilson-Ewing: But ultimately we'd like to make contact with nature and the black holes that we've observed and know of are rotating.

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Edward Wilson-Ewing: And so, if we want to make contact with these black holes that we've we've observed, will have to go beyond strictly symmetric black holes and include angular momentum.

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Edward Wilson-Ewing: And, of course, this will make everything much more complicated, but eventually, I think we are you'll have to go in that direction so just to end, let me give a very ambitious wish list of things that.

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Edward Wilson-Ewing: would be nice to be able to handle going forward, of course, this is not something that will be able to address and just you know up a few papers, but hopefully it gives an idea of.

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Edward Wilson-Ewing: build the the road ahead in the distance so first if we could have a farm description of rotating black holes, be able to follow their dynamics through their entire lifetime from collapse to their eventual disappearance.

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Edward Wilson-Ewing: i'd be able to address information last problem detail so really be able to track.

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Edward Wilson-Ewing: What happens.

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Edward Wilson-Ewing: We nice to be able to include the effective accretion So if you have an accretion desk or in a black hole How does that modify the picture, presumably, there are some fun corrections to qualify normal modes.

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Edward Wilson-Ewing: Can we calculate what those would be and then finally.

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Edward Wilson-Ewing: Can we look calculate the INSPIRE merger and rundown of binary quantum black holes, so of course this is very ambitious, but hopefully this is something that we can aim for in the years to come, so thank you for your attention.

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Abhay Vasant Ashtekar: Thank you very much ED so now, the floor is open for questions to both ED and to Thomas.

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Abhay Vasant Ashtekar: Comments questions.

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Abhay Vasant Ashtekar: Okay, so why people are thinking.

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simone: Every session a list of.

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simone: A lot, please.

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Okay.

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Laurent Freidel: Thank you for these presentations equation to Tomas in fact.

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Laurent Freidel: there's a strategy for the organization constraints that you haven't been.

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Laurent Freidel: That you haven't mentioned in your talk, which in fact has been very fruitful in the past in the recent years, so what we have been doing the best recent years is.

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Laurent Freidel: Using the property, because when, which is that even if the constraint is satisfied in the park, if you would say cut your spin forming a half or cultural space in.

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Laurent Freidel: Then the constraints, you know under boundary needs to implement symmetry algebra transformation and then.

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Laurent Freidel: Which means that even if you have a proposal for the constraints is then you can look at.

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Laurent Freidel: This imagery transformations on demand tree that your quantum constraints generates and then check whether the symmetry is anomalous form and after brides at the hotel so using the strategy, in fact.

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Laurent Freidel: Back end it like you know, starting from what what is the classical symmetry and cut.

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Laurent Freidel: We were you know, we have been able to to quantifies, for instance, properly the different offers and constraints in the book Nadia melton, but I think this is a very important strategy, which has led to another.

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Laurent Freidel: Recent progress on our understanding of quantum constraints, and in fact connects with a lot of literature vs metrics, so I think this is an important point that wasn't mentioned there.

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Abhay Vasant Ashtekar: Okay, Thomas do you want to respond oh.

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Thomas Thiemann: yeah sorry I did not have time to go into all these details, but in fact this is what I meant by.

468
01:08:28,560 --> 01:08:41,340
Thomas Thiemann: stating the question is the spin form amplitude really defining the rigging map in a product between solutions of the quantum Einstein equations, which of course includes the spatial different offers and constraint.

469
01:08:44,010 --> 01:08:46,290
Abhay Vasant Ashtekar: Okay, so basically you agree, but just that.

470
01:08:46,320 --> 01:08:46,530
I.

471
01:08:48,240 --> 01:08:53,220
Abhay Vasant Ashtekar: didn't have time to elaborate next question is from by old gang.

472
01:08:57,780 --> 01:08:58,230
Abhay Vasant Ashtekar: again.

473
01:08:58,920 --> 01:09:04,710
Wolfgang Wieland: Hello everybody hello, thank you for for this nice opportunity and this Nice.

474
01:09:05,790 --> 01:09:07,260
Wolfgang Wieland: Talks so I have.

475
01:09:08,760 --> 01:09:13,410
Wolfgang Wieland: More like perhaps a suggestion, but also a common so.

476
01:09:14,460 --> 01:09:20,130
Wolfgang Wieland: The first two talks they mentioned the flatness problem is one of the.

477
01:09:22,650 --> 01:09:36,690
Wolfgang Wieland: main issues in folk hawaiian to quantum gravity and this seems to be no consensus so different opinions and on the other hand, if we look at economic loop on gravity or.

478
01:09:37,890 --> 01:09:49,440
Wolfgang Wieland: Even more so look on cosmology days, no such problem known So what do we learn from these approaches from from the other side, and is there any.

479
01:09:52,020 --> 01:09:53,490
Wolfgang Wieland: Could we imagine any.

480
01:09:54,720 --> 01:10:05,310
Wolfgang Wieland: kind of cross fertilization and understanding one program from the other side, and why doesn't appear, so this is kind of a suggestion and a comment thanks.

481
01:10:05,850 --> 01:10:20,850
Abhay Vasant Ashtekar: yeah that's very nice question that I think Thomas mentioned that there are these political spin forms, where one can go back and forth between canonical theory and quantum theory, but the problem is that in that case, one is really using the matter you know very, very.

482
01:10:22,020 --> 01:10:28,800
Abhay Vasant Ashtekar: strongly, whereas in spin forms people don't use matter and so that that makes it difficult to go back and forth.

483
01:10:28,860 --> 01:10:29,760
Jerzy Lewandowski: Between the two things.

484
01:10:30,030 --> 01:10:37,680
Abhay Vasant Ashtekar: But I agree with you that this is a good thing to talk about right exactly okay The next question is by Jonathan.

485
01:10:41,520 --> 01:10:56,490
Jonathan Engle: hi um I just had a couple of questions for Thomas so when you i'm not so familiar with them with this result, about the anomalous structure functions, but so my first confusion there's usually.

486
01:10:57,540 --> 01:11:09,540
Jonathan Engle: I mean the the usual way we define different more physics and quantum gravity is not generated by anything there's no the the generators don't exist in the hilbert space so i'm confused with what's being used in that.

487
01:11:11,250 --> 01:11:16,530
Jonathan Engle: In that commentator there for that, for the different more physical constraints and um and the other question was.

488
01:11:18,720 --> 01:11:28,740
Jonathan Engle: Even if the the structure functions are not equal to the classical structure functions are they at least equal in the H bar goes to zero limit appropriately defined.

489
01:11:31,380 --> 01:11:35,760
Thomas Thiemann: to the first question i'm indeed you are correct, on one has to formulate.

490
01:11:37,050 --> 01:11:44,340
Thomas Thiemann: The algebra of constraints using exponential weighted different systems so there's an equivalent way of.

491
01:11:45,300 --> 01:11:53,430
Thomas Thiemann: Finding the also include in the classical view if you use the hamiltonian vector fields of different ways, you can also phrase.

492
01:11:54,030 --> 01:12:02,160
Thomas Thiemann: The algebra in terms of exponential different models and the second question is the answer to the sacrifice and let us know.

493
01:12:02,820 --> 01:12:15,840
Thomas Thiemann: So, even in the age part zero limit the researchers are constants and do not coincide, they have they have there's some fans relation between them, but it's not certainly the classical the Nice classical limit of the quantum.

494
01:12:17,820 --> 01:12:21,060
Thomas Thiemann: The quantum structure Constance is not the one that we expect.

495
01:12:22,110 --> 01:12:22,500
Jonathan Engle: Okay.

496
01:12:23,640 --> 01:12:29,940
Jonathan Engle: And the hamiltonian constraint is a graph preserving or the not the original non graph preserving one.

497
01:12:30,840 --> 01:12:35,250
Thomas Thiemann: So i'm talking to you about the original quantum dynamics version.

498
01:12:38,490 --> 01:12:46,650
Abhay Vasant Ashtekar: Just to continue this question though isn't it true that the various work that mother one has been doing he's actually giving meaning to do.

499
01:12:47,730 --> 01:12:50,070
Abhay Vasant Ashtekar: not explain initiated if you Marxism constraint.

500
01:12:51,690 --> 01:12:59,760
Thomas Thiemann: Well, this is this is possible Okay, now we go really into technical details, this is possible if you if you change the density wait.

501
01:13:00,360 --> 01:13:12,810
Thomas Thiemann: right if you go to a space of distributions and so you have to we're talking here really about different versions of the of the operator on different spaces and different country different versions.

502
01:13:13,590 --> 01:13:18,750
Abhay Vasant Ashtekar: Right, so I just wanted to just make people aware that there is actually way of looking at it from.

503
01:13:19,950 --> 01:13:24,180
Abhay Vasant Ashtekar: Just this changing the density wait to give meaning to.

504
01:13:26,490 --> 01:13:35,760
Abhay Vasant Ashtekar: Not the explanation it, but just a few more some constraint itself and some of the work which relates, the hamiltonian constraint writing it as a defeat some constraints.

505
01:13:36,060 --> 01:13:36,870
Abhay Vasant Ashtekar: has to do with.

506
01:13:37,140 --> 01:13:37,920
Abhay Vasant Ashtekar: writing the.

507
01:13:39,180 --> 01:13:48,210
Abhay Vasant Ashtekar: Different moves and the constraint correspondent we just infinitive will defeat modernism not find it Okay, so my next question.

508
01:13:48,570 --> 01:13:51,300
Thomas Thiemann: This is exactly the second part with I was mentioning.

509
01:13:52,620 --> 01:13:52,980
Abhay Vasant Ashtekar: But.

510
01:13:53,550 --> 01:14:03,690
simone: Thanks listen is for the people working on the reduced face please quantization that was mentioned the by Thomas is one of the approaches, I hear them sometimes.

511
01:14:05,400 --> 01:14:13,470
simone: Seeing that the model used is not very phenomenal logical, so they should be improved, but fine I mean i'm happy with a.

512
01:14:14,160 --> 01:14:21,840
simone: With a non very phenomenology galley duster the questions really interesting are maybe even just validity once.

513
01:14:22,110 --> 01:14:26,490
simone: Like are they singularities resolved what happens at the end of the operation of a black hole.

514
01:14:26,790 --> 01:14:40,050
simone: So use whatever that you have, but is it possible to try to answer these questions, just at a qualitative level in these models, or if not, what are the difficulties there, I mean it's been bombs, we have some.

515
01:14:41,130 --> 01:14:47,940
simone: technical difficulties, of course, and i'm wondering if there are also technical difficulties there, or if it's more contextual Thank you.

516
01:14:52,050 --> 01:15:02,850
Thomas Thiemann: i'm not sure who's supposed to answer, but I can try um so there's there's work in this direction that tries to use a semi classical techniques.

517
01:15:03,930 --> 01:15:09,000
Thomas Thiemann: To somehow monitor the evolution of the singularity when you follow.

518
01:15:10,020 --> 01:15:17,130
Thomas Thiemann: The expectation value inside a coherent state, yes, yes, some work along those lines, but.

519
01:15:18,390 --> 01:15:24,510
Thomas Thiemann: Coming back to the phenomenon electrical relevance, I mean, I think this is a serious problem, I mean.

520
01:15:26,520 --> 01:15:33,540
Thomas Thiemann: Because when you when you add this doesn't new changing the degrees of freedom of the of the theory, and this has a serious impact.

521
01:15:35,250 --> 01:15:42,570
simone: But let me just call it okay so you're changing the dynamics, but he's the singularity resolved or not is the is there a remnant suppose.

522
01:15:42,930 --> 01:15:55,800
simone: OK, we might see that will result is not back up because it's using the summer DAS, which is non physical bearskin like getting all the way to the result at the end I think you'll be very valuable, even if there is discovery of course.

523
01:15:56,940 --> 01:16:04,950
Thomas Thiemann: Okay, this this is this cannot be answered at the moment because the metaphor theory these calculations are much more complex and.

524
01:16:07,560 --> 01:16:16,380
simone: So there are technical challenges to be overcome in order to be able to use these parameters and models for answering these questions they go to someday.

525
01:16:17,700 --> 01:16:23,760
Thomas Thiemann: I would say, you can try to follow the same steps as an advocacy, but of course the calculations are going much more complex.

526
01:16:26,250 --> 01:16:26,520
Abhay Vasant Ashtekar: Okay.

527
01:16:26,670 --> 01:16:27,840
Abhay Vasant Ashtekar: So I think it next is.

528
01:16:28,170 --> 01:16:29,130
Abhay Vasant Ashtekar: One again.

529
01:16:32,280 --> 01:16:34,770
Ivan Agullo: hey, this is a question for ED.

530
01:16:35,940 --> 01:16:39,180
Ivan Agullo: And is somehow related with with Simone is common.

531
01:16:40,530 --> 01:16:52,740
Ivan Agullo: amazing I just would like to you to expand a little bit in one of the things that you mentioned in in the part of ltc a you mentioned that one of the desire.

532
01:16:53,820 --> 01:17:06,090
Ivan Agullo: avenues is to relate LPG without QC in a more concrete manner, but somehow What you said is that desire is a bit of her intention with what Thomas said.

533
01:17:06,630 --> 01:17:10,290
Ivan Agullo: Thomas explained to us that there is no well gee that we all agree with.

534
01:17:10,890 --> 01:17:30,930
Ivan Agullo: That is no hamiltonian constraint that we all agree with that is a huge amount of ambiguity and we don't know what, which is the day they prefer one so so if, therefore, if there is no such uncle G, you could do they'll ask you to view about these relation between mtg and okay.

535
01:17:32,280 --> 01:17:39,630
Edward Wilson-Ewing: Right, so I think there are two statements there, so the first one, I agree, I think there's a lot of quantization ambiguity and we're not quite sure.

536
01:17:40,110 --> 01:17:51,540
Edward Wilson-Ewing: You know which choices are the physically appropriate ones, but there are choices that have been made right, so you hit some monetization ambiguous and you can just say okay well let's just choose this and see what happens.

537
01:17:52,350 --> 01:17:59,400
Edward Wilson-Ewing: And so it is possible to come up with some you know hamiltonian constraint operator and just see what happens on a certain type of state.

538
01:18:00,960 --> 01:18:03,000
Edward Wilson-Ewing: And then the question is, can we somehow.

539
01:18:04,170 --> 01:18:07,890
Edward Wilson-Ewing: map that to El que si at least approximately.

540
01:18:09,120 --> 01:18:18,090
Edward Wilson-Ewing: And I mean of course that there's there's a lot to be done here, but my hope would be that this could give some insight into.

541
01:18:18,750 --> 01:18:30,660
Edward Wilson-Ewing: what works and what doesn't work so probably you know, the first time you'll try something and it won't quite work, but it may give you some hints as to what steps along the way, might have to be changed, and what way.

542
01:18:32,010 --> 01:18:46,440
Edward Wilson-Ewing: So I don't think it's just a question of taking you know Luke quantum gravity and you know just say Okay, this is the right state, and then we get ltc it's more saying what are we have all these ambiguities let's try and make some choices and see what we get.

543
01:18:47,670 --> 01:18:48,420
Edward Wilson-Ewing: and

544
01:18:49,470 --> 01:18:56,190
Edward Wilson-Ewing: You know, maybe we'll be lucky and we'll get something that it's close to ltc maybe we won't be but hopefully by going through that process we get some insight.

545
01:18:56,640 --> 01:19:08,940
Edward Wilson-Ewing: into what choices seem to be working what steps along the way we more or less understand which ones we don't and also give some hints as to which ambiguities, or which.

546
01:19:09,990 --> 01:19:13,590
Edward Wilson-Ewing: choices for some of these ambiguity is maybe more physically appropriate.

547
01:19:15,780 --> 01:19:17,370
Abhay Vasant Ashtekar: Exactly what is being done right.

548
01:19:17,970 --> 01:19:19,350
Edward Wilson-Ewing: Now absolutely yeah.

549
01:19:19,530 --> 01:19:20,460
Edward Wilson-Ewing: i'm just saying like.

550
01:19:20,520 --> 01:19:21,510
Edward Wilson-Ewing: I think we're.

551
01:19:22,410 --> 01:19:23,400
Edward Wilson-Ewing: very nice work there.

552
01:19:23,550 --> 01:19:25,530
Edward Wilson-Ewing: But there's a lot more to be done, still right.

553
01:19:25,770 --> 01:19:31,170
Abhay Vasant Ashtekar: So this, so this is a divine died, I mean, in particular, work that you want himself as.

554
01:19:33,150 --> 01:19:37,350
Abhay Vasant Ashtekar: is really along the same lines right, I mean, namely that choose some.

555
01:19:38,760 --> 01:19:47,730
Abhay Vasant Ashtekar: ideas of coin states or you know and then choose a certain hamiltonian and then see if, in fact, the if you take the expertise and values.

556
01:19:48,120 --> 01:19:57,240
Abhay Vasant Ashtekar: The questions we get asked the same similar to the equations of effective questions about you see and do art extend they are two artists and they're not.

557
01:19:57,780 --> 01:20:01,860
Abhay Vasant Ashtekar: And I think that that is providing some guidance, because they do give different answers.

558
01:20:02,640 --> 01:20:09,690
Abhay Vasant Ashtekar: Before the big bang they seemed all agree with with standard QC after the big bang bang, so I think this is food for.

559
01:20:10,050 --> 01:20:22,380
Abhay Vasant Ashtekar: Thought and I kind of felt that this is along the lines of ED was saying, which is true, which is to say that there are two motivations to look at this models one was contacted observations, but second was partial guidance for the full.

560
01:20:23,520 --> 01:20:27,600
Abhay Vasant Ashtekar: The development of the full day, so I think this is that spirit is that right.

561
01:20:28,320 --> 01:20:29,130
Edward Wilson-Ewing: yeah absolutely.

562
01:20:29,670 --> 01:20:33,630
Ivan Agullo: I agree, but I just thought that this is is good for everybody to save explicitly.

563
01:20:36,150 --> 01:20:36,480
Abhay Vasant Ashtekar: Okay.

564
01:20:36,600 --> 01:20:37,200
The anchor.

565
01:20:38,670 --> 01:20:39,720
Bianca Dittrich: Is that's an.

566
01:20:39,810 --> 01:20:40,950
Edward Wilson-Ewing: answer to.

567
01:20:41,010 --> 01:20:57,780
Bianca Dittrich: Work on this question so First let me actually really see that is large agreement on the flatness constraints, so there are two different and completely independent mechanisms that the flatness constraint, this is all in the continuum limit.

568
01:20:58,920 --> 01:21:10,260
Bianca Dittrich: And of course it would be nicer to see more calculations of non productive spin from petition functions and that, indeed, is about calculation methods, but otherwise this would be.

569
01:21:11,700 --> 01:21:13,110
Bianca Dittrich: To completely independent.

570
01:21:14,310 --> 01:21:30,570
Bianca Dittrich: mechanisms which which we had was all about the question this as a pm, etc, and I could see that the ceiling interesting point so ABC I do think that many also deductions, because you also might not capture this issue.

571
01:21:31,620 --> 01:21:41,280
Bianca Dittrich: Because it had also happens if you consider spin form cosmology to some degree, if you, for instance, have just one scale factor, you do not see these additional degrees of freedom.

572
01:21:42,150 --> 01:21:52,560
Bianca Dittrich: And, but these additional degrees of freedom are in the energy, space and you have the same kind of anomaly in the also simplicity constraints.

573
01:21:53,100 --> 01:22:09,960
Bianca Dittrich: So, indeed, that would be interesting to see what happens if you consider a function, for instance, which you know, cannot be suppressed strongly in these discrete degrees of freedom, how does this play function evolve, so the gaussian Peters, for instance.

574
01:22:11,160 --> 01:22:23,880
Bianca Dittrich: preserved and actually Simone ahead a bit of related investigation, but in that case it was kind of on flat base times and need to actually consider this issue and.

575
01:22:24,810 --> 01:22:44,430
Bianca Dittrich: And can only get a G at some point, so it, it does exist, and I do I do saying we haven't really identified get or seen this problem my you know under hamiltonian dynamics and and, indeed, it will be religious question to consider how do these degrees of freedom propagate.

576
01:22:47,070 --> 01:22:49,770
Abhay Vasant Ashtekar: Okay, thank you bianca Christina.

577
01:22:50,820 --> 01:22:55,290
Kristina Giesel: yeah Thank you i'm wanting to move them to a similar question without.

578
01:22:56,400 --> 01:23:08,820
Kristina Giesel: Knowledge of the dust and so we tried to move in this direction to the farm and wants to move to an agency executive at a reduced price quantization, including the dust.

579
01:23:09,330 --> 01:23:18,810
Kristina Giesel: And then, what happens is that of course you would like to inflict on so in the end up with two systems and set up one thing IT systems, you have any other models.

580
01:23:19,470 --> 01:23:25,290
Kristina Giesel: And then you can basically write down the quantum dynamics and the coaching so far removed for the models.

581
01:23:25,890 --> 01:23:31,080
Kristina Giesel: Without the dust need to be extended, but I think this is still possible, but hasn't been done.

582
01:23:31,800 --> 01:23:40,620
Kristina Giesel: And at the effective level, you can ask the question are the initial conditions for the dust such that, for instance, we get information or that the singularity will be resolved.

583
01:23:41,430 --> 01:23:54,660
Kristina Giesel: and district can analyze and very simple model, but of course as Thomas mentioned, you need to extend all the templates that are ready for the agency model so far, because you have this additional degrees of freedom and also fulfill the variations.

584
01:23:54,930 --> 01:24:12,750
simone: could be we're going to do, but are you been seeing that the usual whether the singularity is resolved or not may depend on the initial conditions on the desk because if so, then I understand why you guys are limited in the approach, because that seems very artificial then.

585
01:24:12,960 --> 01:24:13,920
simone: I thought that.

586
01:24:14,160 --> 01:24:16,020
simone: We might be not stronger result.

587
01:24:16,680 --> 01:24:25,770
Kristina Giesel: Well, this I wouldn't say I would say, for inflation will consider us for the other question you really have to analyze the quantum dynamics which hasn't been done so far.

588
01:24:26,250 --> 01:24:39,600
Kristina Giesel: For these two fluid system, and then you can answer the question, but this initial conditions we looked at in the problem factor dynamics and then you can see whether inflation inflation of course unlocks might depend, it will depend on the mistreatment.

589
01:24:42,990 --> 01:24:47,310
Abhay Vasant Ashtekar: Right, but what about singularity retribution Does that also depend on the initial conditions or you.

590
01:24:48,210 --> 01:24:57,150
Kristina Giesel: know as as far as if you if you look at the effective level, but I would say to really answer the question for quantum dynamics.

591
01:24:57,360 --> 01:25:02,940
Abhay Vasant Ashtekar: Right, but for effective dynamics this statement isn't singularities result, but you don't know what happens in the corner.

592
01:25:03,900 --> 01:25:16,290
Kristina Giesel: yeah, and I mean usually you derive effective dynamics from the equations we haven't looked at, so far, so therefore I would say to really make a strong statement, we should look at the quantum mechanics first.

593
01:25:19,500 --> 01:25:19,920
Abhay Vasant Ashtekar: All right.

594
01:25:20,220 --> 01:25:21,600
Abhay Vasant Ashtekar: Daniel has a question.

595
01:25:25,170 --> 01:25:29,070
Daniele Oriti: yeah hello, so I have a question for both the.

596
01:25:30,120 --> 01:25:43,350
Daniele Oriti: canonical quantum gravity in the US Department tries framework and for a loop on to cosmology and it has to do with the fact that in principle we can never as also see Mona was.

597
01:25:44,580 --> 01:26:01,260
Daniele Oriti: Mentioning different material physical reference frames, in which we express our our theory and our physics and I was wondering how much is no not in both contexts about transformations across such a physical reference frames and.

598
01:26:03,660 --> 01:26:08,790
Daniele Oriti: Indeed, what we know about the environment properties across such.

599
01:26:10,170 --> 01:26:10,740
Daniele Oriti: Thanks.

600
01:26:15,300 --> 01:26:16,980
Thomas Thiemann: I can say something about.

601
01:26:17,220 --> 01:26:18,690
Thomas Thiemann: So you're asking the question.

602
01:26:19,770 --> 01:26:23,190
Thomas Thiemann: um when I change my mature reference system.

603
01:26:24,480 --> 01:26:28,380
Thomas Thiemann: What does change physically right, this is your question.

604
01:26:29,340 --> 01:26:42,960
Daniele Oriti: Yes, that you perform the quantization at the best possible level of rigor and success with both that does the monkey will frame and I don't know for scale of fields, or some other.

605
01:26:43,740 --> 01:26:56,580
Daniele Oriti: Physical frame there's no issue with different biases, but we still ask what is, if there is the set of transformations in field space that will not perform one description, to the other.

606
01:26:57,870 --> 01:27:06,570
Daniele Oriti: And what is environment on the structure transformation, of course, the simplified the question applies in cosmology hospital changes in.

607
01:27:09,360 --> 01:27:12,780
Daniele Oriti: The dynamic, so we have two different material clocks.

608
01:27:14,370 --> 01:27:25,740
Thomas Thiemann: Right, so this is that of course at the classical level on me in so let me say one more sentence and made it becomes clearer.

609
01:27:26,640 --> 01:27:33,420
Thomas Thiemann: is reduced faceplates quantization can be also seen as a as an agent version of gauge fixing.

610
01:27:34,230 --> 01:27:41,610
Thomas Thiemann: And as long as you are engaged fixing conditions are related by against on information and then the.

611
01:27:42,330 --> 01:27:48,510
Thomas Thiemann: Descriptions in terms of the tools choices of reference frames are classically absolutely equivalent.

612
01:27:49,320 --> 01:28:02,190
Thomas Thiemann: And then, of course, when you want is there will be differences, for example, when you consider the physical hamiltonian because of ordering issues and so on, was so that is something it's an interesting question which I think has not been.

613
01:28:03,750 --> 01:28:13,230
Thomas Thiemann: Looked at in full data, I mean I think in in in models, with only a finite number of degrees of freedom, you can see much more.

614
01:28:15,180 --> 01:28:16,950
Thomas Thiemann: So that would be in question to add.

615
01:28:19,050 --> 01:28:28,080
Edward Wilson-Ewing: yeah, so I think this is a question that maybe can be answered a little bit more in El que si but I actually am not aware of a whole lot of work that's been done along those lines.

616
01:28:28,440 --> 01:28:37,260
Abhay Vasant Ashtekar: So there's some work that was done long time ago that was, I think, with Google and when you date we look, this is in the context of cosmology only so.

617
01:28:37,740 --> 01:28:38,460
Abhay Vasant Ashtekar: So the.

618
01:28:38,700 --> 01:28:43,530
Abhay Vasant Ashtekar: The exactly the question that then he was asking this really restricted framework.

619
01:28:45,360 --> 01:28:55,380
Abhay Vasant Ashtekar: Namely, what we did was to have two different notions of flux and see, in fact, if you know, is a physics invariant and and it is notional clock different.

620
01:28:56,160 --> 01:29:04,590
Abhay Vasant Ashtekar: So what happens is that if you do use one notion of plot, then you get some setup observers if you get another notion of clocks you get another set of opposite of those because.

621
01:29:05,070 --> 01:29:12,120
Abhay Vasant Ashtekar: The observers of algebra depends on the the the parameter ization that you are you actually done.

622
01:29:12,990 --> 01:29:20,820
Abhay Vasant Ashtekar: And then, in that case, however, we were able to find astutely observable and show that in fact there is there is equivalence between.

623
01:29:21,300 --> 01:29:26,040
Abhay Vasant Ashtekar: The parameters in one way or the parameters in another way, so this was done very.

624
01:29:26,820 --> 01:29:33,810
Abhay Vasant Ashtekar: uncommon cosmology in a very simple one example and that's also that, but there is such an example in which back to the one has been able to compare.

625
01:29:34,590 --> 01:29:41,790
Abhay Vasant Ashtekar: But I think in the final you probably noticed any later Philip Horn has been doing a lot of work in the finance automation systems.

626
01:29:42,510 --> 01:29:49,440
Abhay Vasant Ashtekar: And so there one understands reasonably well, and you have to be careful about talking about relational observable so.

627
01:29:50,250 --> 01:29:58,710
Abhay Vasant Ashtekar: Many shades of meaning of our various observers that one gives and then this has been analyzed in some in quite some detail, but I guess.

628
01:29:59,670 --> 01:30:07,140
Abhay Vasant Ashtekar: I think that Philip himself had done something in cosmology but maybe not i'm wrong, but I think what maybe somebody has did something, because what are you using the inside.

629
01:30:07,740 --> 01:30:10,380
Bianca Dittrich: That actually you should definitely an ankle.

630
01:30:10,380 --> 01:30:12,210
Abhay Vasant Ashtekar: yeah exactly Stefan exactly Thank you.

631
01:30:12,600 --> 01:30:20,910
Bianca Dittrich: Have interesting peoples and it shows that there are differences, if you choose different clocks in particular that also relates to some.

632
01:30:21,960 --> 01:30:34,080
Bianca Dittrich: rocket timely, because what you get depends on how your clock a purchase singularity and so you can actually make very general statements, whether you singularity is resolved.

633
01:30:34,590 --> 01:30:52,110
Bianca Dittrich: or not, depending on how the clock be like, is it the wellness materia portraying it or not, and that is if you insist on a unitary time evolution with respect to this clock, so I recommend these people's brains definitely yeah.

634
01:30:52,140 --> 01:30:56,910
Abhay Vasant Ashtekar: I did a very nice paper, but I did have the schedule is different on that, and there are certain limitations of their.

635
01:30:58,470 --> 01:31:06,450
Abhay Vasant Ashtekar: Their their work they do not take into account certain subtleties which I like to reconnect again, which are important conceptual stuff, it is important.

636
01:31:06,840 --> 01:31:14,490
Abhay Vasant Ashtekar: If anybody's interested I can think about it, and you know reply to an email about it, but I did have a ministry fundamental may be able to.

637
01:31:15,510 --> 01:31:15,810
Abhay Vasant Ashtekar: me.

638
01:31:16,680 --> 01:31:26,280
Thomas Thiemann: I also recall some just all I remember that the uncle me bro the water paper um I think in 2007 will be sure that for.

639
01:31:27,390 --> 01:31:28,170
Thomas Thiemann: You can have.

640
01:31:29,460 --> 01:31:34,380
Thomas Thiemann: You can cook up final dimensional models which have the property that.

641
01:31:34,950 --> 01:31:42,240
Thomas Thiemann: Whether you when you need when you choose one clock or the other, you can have observed the chef discreet or continue spectrum, you can have.

642
01:31:42,570 --> 01:31:54,390
Thomas Thiemann: Two or even just continuous discrete spectrum and so on, so all possible combinations of possible and I think this is going to read, because you cannot say anything structurally independent.

643
01:31:55,740 --> 01:32:00,810
Abhay Vasant Ashtekar: If you compare the tillage one would need to have a common observers between the two theories, otherwise there's no contradiction.

644
01:32:01,950 --> 01:32:03,630
Abhay Vasant Ashtekar: Right or are you saying there's a contradiction.

645
01:32:05,010 --> 01:32:10,170
Abhay Vasant Ashtekar: In contradiction right, so the statement is that you just get two different descriptions right, I mean.

646
01:32:10,410 --> 01:32:19,710
Abhay Vasant Ashtekar: This, this is a setup officer Was this a hilbert space and these a prediction for this observers and then, here is another set of observers here is the input space here is a prediction for themselves time a regional observers.

647
01:32:20,400 --> 01:32:26,130
Abhay Vasant Ashtekar: But that is not satisfactory one would like to have the relation between the two, and that is often very, very difficult.

648
01:32:26,490 --> 01:32:28,290
Thomas Thiemann: yeah the wallpaper, that is what when.

649
01:32:28,740 --> 01:32:40,110
Thomas Thiemann: You assess the little bit similar to the question what What is so special body and national friends, most of us are saying singled out by you know by the old property that.

650
01:32:41,970 --> 01:32:48,120
Thomas Thiemann: force list particles are moving on straight lines, and if you go to an accelerated friend and things change and.

651
01:32:49,650 --> 01:32:51,060
Thomas Thiemann: So I think this is very soon.

652
01:32:52,200 --> 01:33:03,510
Bianca Dittrich: yeah No two, three, I buy your rights civil different observers, but see they kind of the same partial job it's, but this is different clocks.

653
01:33:04,650 --> 01:33:16,770
Bianca Dittrich: So that was a point that you can change the clock and have kind of the same consider the same field, for instance, and then you have different spectrum.

654
01:33:17,850 --> 01:33:19,200
Bianca Dittrich: But then there are different.

655
01:33:20,430 --> 01:33:22,290
Bianca Dittrich: Environment observers fully.

656
01:33:23,850 --> 01:33:27,150
Bianca Dittrich: In the different technical service, of course, which you consider when.

657
01:33:29,490 --> 01:33:32,880
Abhay Vasant Ashtekar: I think Daniela you're still want to ask something and then we can close.

658
01:33:33,600 --> 01:33:42,990
Daniele Oriti: Just a couple of comments or, if I understand correctly, from your answer, so the point is that we should expect the physical notion of general covariance.

659
01:33:43,470 --> 01:33:58,230
Daniele Oriti: That not necessarily an imbalance in the description, so we should be able to translate it from a physical frame when other one with some vegetables map and so on, so that we can always communicate what we observe in different frames.

660
01:33:59,250 --> 01:34:06,330
Daniele Oriti: Different choice of pubs and clubs, but we should not be in general, expect that they will be invited on quantities that we agree.

661
01:34:07,350 --> 01:34:14,190
Daniele Oriti: In the description, meaning that they are in fact being bought up under such transformations in in the medical value or in the spectrum.

662
01:34:15,540 --> 01:34:22,080
Daniele Oriti: So sensible, I want to check that understood this correctly, but if it so it seems, in fact, the resonant with what.

663
01:34:23,160 --> 01:34:39,510
Daniele Oriti: filipa has been finding in the in the know this notion of quantum general covariance mapping from one action to the physical frame to another one true, in fact, the framing dependent description.

664
01:34:40,800 --> 01:34:52,230
Daniele Oriti: So there's the first comment, the second comment is that i'm a little i'm not i'm not sure that I understood the business reply by Thomas referring just for the classical theory.

665
01:34:52,980 --> 01:35:03,900
Daniele Oriti: So the idea that you can you can understand the reduction to the theory with particular physical framer as exactly the counterpart over gauge fixing.

666
01:35:05,070 --> 01:35:21,360
Daniele Oriti: And so that you know if you do it the classical level into the respite to two different frames up your spec exact equivalence of the true or it's a teen violence, in fact, in the case because this indeed is just like a gauge fixing because.

667
01:35:22,740 --> 01:35:30,420
Daniele Oriti: i'm not so convinced that I wouldn't be surprised if that's the case because what i'm talking about actually physical systems.

668
01:35:31,140 --> 01:35:39,840
Daniele Oriti: And the physical system that we decide to use us frames will back react on the on the geometry will have their own non trivial dynamics.

669
01:35:40,740 --> 01:35:49,920
Daniele Oriti: In a particular limited approximation, I could expect that they behave, just like according to frame and so reducing to that is equivalent to engage fixing.

670
01:35:51,150 --> 01:35:57,060
Daniele Oriti: Of the difference in Africa in general on physical grants, I would be surprised if that's the case.

671
01:35:58,110 --> 01:35:58,890
Abhay Vasant Ashtekar: The anchor.

672
01:36:01,590 --> 01:36:03,060
Bianca Dittrich: It is classical is a key.

673
01:36:04,920 --> 01:36:05,670
Bianca Dittrich: I mean that.

674
01:36:09,570 --> 01:36:16,200
Bianca Dittrich: It was quantities, it was a reduced reduction reduction is equivalent to a family of eight fixings.

675
01:36:20,310 --> 01:36:28,860
Bianca Dittrich: So it's a family of patriots things and you still have different choices for you for this family and that can also lead to differences, of course.

676
01:36:33,630 --> 01:36:41,010
Abhay Vasant Ashtekar: yeah I mean, of course, his family has to be good against fixings right, in other words what Danielle his point was that.

677
01:36:42,180 --> 01:36:45,120
Bianca Dittrich: No back reaction and so on yeah but so so yeah.

678
01:36:45,300 --> 01:36:47,700
Bianca Dittrich: I mean becky action is not the issue, the issue.

679
01:36:48,180 --> 01:36:50,850
Abhay Vasant Ashtekar: No, but, but it could be done because a bad reaction.

680
01:36:50,850 --> 01:36:53,040
Abhay Vasant Ashtekar: Something that you might think has been obviously good.

681
01:36:53,940 --> 01:36:56,010
Bianca Dittrich: yeah so famous this fixing.

682
01:36:56,370 --> 01:37:02,130
Bianca Dittrich: famously if you have something for the Arctic and the constraints and it's difficult to find good catch fixings yeah.

683
01:37:02,160 --> 01:37:16,590
Abhay Vasant Ashtekar: So what do we need to do, I mean compared this systems with good kitchen fixing, but other than yours you're saying me know if you if you do, let me try different kinds of scale of fields or dust, then this is good gets fixing right.

684
01:37:17,730 --> 01:37:31,200
Daniele Oriti: OK, so the statement applies it to a subset of the possible physical systems or users afraid those that allow for this exact the parameter ization and that can be shown to be equivalent to each fixing.

685
01:37:31,770 --> 01:37:37,950
Daniele Oriti: While the systems every mind wearing principles, you know the most general ones that we may crazy clock and increasing set routes.

686
01:37:38,430 --> 01:37:48,870
Daniele Oriti: That are not less physical because they're not perfect clocks and perfect drops by their physical systems as well, it will be probably a stupid choice to to use to some of them as.

687
01:37:48,870 --> 01:37:49,080
Abhay Vasant Ashtekar: You go.

688
01:37:50,340 --> 01:37:51,390
Daniele Oriti: about the Channel number one.

689
01:37:51,900 --> 01:37:57,840
Abhay Vasant Ashtekar: there'll be bad against fixing typically and o'clock which is sitting there that business value is fixing so that nothing.

690
01:37:59,700 --> 01:38:01,560
Abhay Vasant Ashtekar: Okay, I think, if there are no further questions.

691
01:38:01,560 --> 01:38:10,080
Abhay Vasant Ashtekar: it's a hour and 40 minutes or should quit so last chance if anybody has a question i'm looking at the chat box also if anybody raises hands.

692
01:38:13,920 --> 01:38:23,160
Abhay Vasant Ashtekar: Okay, I don't see any hands so so the ideas as the Mona said was that this would be this a nice Christmas present, but the panelists to all of us.

693
01:38:23,490 --> 01:38:38,250
Abhay Vasant Ashtekar: There is several issues that we can model or the Semester break and then come with Nice ideas for the 2022 so happy holidays and Happy New Year everybody and we'll meet again next year.

694
01:38:39,510 --> 01:38:40,500
Jorge Pullin: it's time for speakers.