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Jorge Pullin: first speaker to this rubber brandon burger will speak about alternative supersizing of inflation, Robert.

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Robert Brandenberger, Prof.: Right so first of all thank you for the invitation to.

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speak.

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Robert Brandenberger, Prof.: it's a great pleasure and I have a couple of messages, so the first message is that inflation is not the only other universe scenario what is consistent with observations.

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Robert Brandenberger, Prof.: and makes predictions for future observations, there are others, and the second message is that people working on quantum gravity should, in my opinion, not try to introduce ad hoc skater fields into their models because first of all, it is not needed and, secondly, it is problematic so.

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Robert Brandenberger, Prof.: This is the specific outline of the talk, I will first present you with a number of scenarios, with which the current data can be explained then I will remind you of what inflationary scenario is and why it is facing serious conceptual problems coming from I believe quantum gravity.

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Robert Brandenberger, Prof.: And I was asked to focus on bouncing cosmologists, so I will then move on and talk about the balancing scenario which I think is the most promising, namely the erotic bouncing scenario.

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Robert Brandenberger, Prof.: And I will show how you can.

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Robert Brandenberger, Prof.: save some of the problems of extra erotic cosmology by introducing this s brain concept.

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Robert Brandenberger, Prof.: Now I will show you the predictions that come from this scenario, and if I have time I will also talk about models of emergent cosmology.

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Robert Brandenberger, Prof.: motivated by string theory, but there are probably other models of emerging cosmology which are not available other models of quantum gravity and you can probably use the same tools which we use to study perturbations also in these other models, so this is a menu for this morning.

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Robert Brandenberger, Prof.: So we are in traffic in the data in the context of standard big bang cosmology where the universal mode from a hot fireball and 300,000 years after the fireball the plasma recombined the microwave background was released.

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Robert Brandenberger, Prof.: And one of the key things that we would like to explain about the data is the I saw trippy of the microwave background.

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Robert Brandenberger, Prof.: So this is a projection of the sky onto a plane and it shows you the intensity of the microwave background in all directions in the sky, and it is this incredible I saw therapy, which has no explanation standard big bang cosmology.

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Robert Brandenberger, Prof.: Now, if you probe deeper one thought intend to the four, then you see hotspots and cold spots emerging.

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Robert Brandenberger, Prof.: And again, the origin of the structure, it cannot be explained standard big bang cosmology, and so it is a challenge for quantum gravity to come up with an explanation.

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Robert Brandenberger, Prof.: So these an assault is can be quantified, so we expand the map in circle harmonics and we plot the intensity, which is the vertical axis as a function of angliss game.

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Robert Brandenberger, Prof.: Is horizontal axis and then the data is the black dots were statistical errors on small angular scales in a little bit of systematic uncertainty on large angular scales.

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Robert Brandenberger, Prof.: And there's an artist who was given six parameters to fit the this data and the red curve, is the product of what is artists provided and i'm not going to tell you, who this artist was.

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Robert Brandenberger, Prof.: So they are two artists who independently came up with an explanation for this data, in fact, who predicted this data.

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Robert Brandenberger, Prof.: And one set of artists as individuals in the if the other our keyboards and you and they did this artwork in 1969 1970 which is 10 years before the development of inflationary cosmology.

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Robert Brandenberger, Prof.: plot from the paper which is unique.

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Robert Brandenberger, Prof.: So the vertical axis is time because our blocks is.

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Robert Brandenberger, Prof.: A space co moving coordinates.

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Robert Brandenberger, Prof.: Here, if you see my cursor is a time when the microwave background was in the was released this diagonal line is the standard big bang horizon which.

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Robert Brandenberger, Prof.: Will should be called hubble radius and TV, he is and empower people send you assumed that there was a spectrum of density perturbations on large scales on these super horizon scales imprinted India universe.

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Robert Brandenberger, Prof.: And such a spectrum of density perturbations was no not ready 1970 to be a good description of the distribution balances.

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Robert Brandenberger, Prof.: So what they pointed out, is that different wave different ways, so I have a radius at different times.

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Robert Brandenberger, Prof.: The waves of frozen in why the wavelength is larger than the hub radius and they start to oscillate when the wavelength enters the hub or, I guess, so the wave was crosses which enters the hubble radius right at the time of recombination that corresponds to one degree in the sky.

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Robert Brandenberger, Prof.: It has had no time to oscillate and we catch it at maximal.

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Robert Brandenberger, Prof.: amplitude, whereas the way that has an accord of an oscillation we catch it at a local minimum of amplitude and so on and so this picture it predicted this nice curve of acoustic oscillations in the cosmic microwave background.

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Robert Brandenberger, Prof.: So this is what I like to.

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Robert Brandenberger, Prof.: Now, the figure in the zelda which city is paper at the second part, and the second part shows you the matter power spectrum as a function of wave number, and he same oscillations of the berry on photon fluid.

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Robert Brandenberger, Prof.: In print these Baron across the constellations into the power spectrum of Mike have multiple production.

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Robert Brandenberger, Prof.: So, of course, the constellations in the microwave background bearing across the constellations in a matter of our spectrum we're well understood in 1969 1978 10 years before the development of inflation.

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Robert Brandenberger, Prof.: But the one question which was not explained back in 6970 is how does one obtain such a spectrum.

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Robert Brandenberger, Prof.: And indeed, inflation is the first scenario based on cost of physics, which yields a roughly ski and Ryan spectrum of cosmological perturbations on scales, which are super humble, from the point.

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Robert Brandenberger, Prof.: But it is not the only one.

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Robert Brandenberger, Prof.: What are the criteria.

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Abhay Vasant Ashtekar: For success, but can I just ask you a question about the very nice historical background, you gave us, so what is the model of treatment model that they used in this earth from the big bang until you know.

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Robert Brandenberger, Prof.: standard.

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Abhay Vasant Ashtekar: Bank as follows, so but but is this supposed to be resistant and the time or.

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Robert Brandenberger, Prof.: So you see, they did not answer the question, where does the spectrum come from.

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Abhay Vasant Ashtekar: No, but but still got the hubble horizon and so she could not read everything.

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Abhay Vasant Ashtekar: So yeah how about your eyes and must.

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Robert Brandenberger, Prof.: Just be by horizon.

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Robert Brandenberger, Prof.: yeah this picture here.

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Abhay Vasant Ashtekar: that's going to need.

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Abhay Vasant Ashtekar: liquid don't you need a matter content some sort of Meta content to get.

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Robert Brandenberger, Prof.: started matter Marianne radiation food.

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Abhay Vasant Ashtekar: Better medicine so it's not just reason, because both Saturday.

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Robert Brandenberger, Prof.: Is standard big bang cosmology with with a matter and with the radiation that we observe and.

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Robert Brandenberger, Prof.: yeah.

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Robert Brandenberger, Prof.: And I think the dark matter was already included back then.

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Okay.

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Robert Brandenberger, Prof.: So now, if we want to produce.

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Robert Brandenberger, Prof.: fluctuations on scales, which are larger than the standard big bang horizon.

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Robert Brandenberger, Prof.: You know, cause away, and if you want to expand the is how to be at the microwave background, then the first criterion for successful universe scenario is that the horizon has to be much bigger than the hubble radius.

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Robert Brandenberger, Prof.: And second criteria set scales that we observe today, they have to originate at early times inside of a hubble radius, otherwise we can't move matter around on a short time scale to produce fluctuations.

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Robert Brandenberger, Prof.: And finally, if we manage to come up with a scenario which satisfies the first two criteria, it should also produce a roughly skating around spectrum of cognitive renovations.

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Robert Brandenberger, Prof.: So these are the three criteria for a successful or the universe scenario and inflation indeed satisfies all three criteria.

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Robert Brandenberger, Prof.: So this is a space time diagram of inflation vertical axis time horizontal axis is space and the time interval from piece of identity, so bar is the hypothetical time interval where space is supposed to expand almost expect.

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Robert Brandenberger, Prof.: An inflationary cosmology there's a big bang singularity.

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Robert Brandenberger, Prof.: But during the time of expansion expansion of space, the horizon expands exponentially relative to the huddle radius.

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Robert Brandenberger, Prof.: So therefore.

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Robert Brandenberger, Prof.: criterion, one can be satisfied.

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Robert Brandenberger, Prof.: Now if iteration as long enough, then scales and we observe today this red line is the physical wavelength of density perturbations that we measure today, for example, a quarter pole of the microwave background.

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Robert Brandenberger, Prof.: So if inflation last long enough, then this wavelength is smaller than a hugger radius at the beginning of inflation.

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Robert Brandenberger, Prof.: And we can come up with a causal generation mechanism.

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Robert Brandenberger, Prof.: And the time translation invariance of the visitor phase will guarantee that the perturbations that are produced are roughly skating down, this is a realization that was first made by Bill plus and for gravitational waves by Alex a stove in ski and independently, but ubisoft.

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Robert Brandenberger, Prof.: Now here's a second criteria, was a second model scenario in which you can satisfy all three criteria for successful universe cosmology.

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Robert Brandenberger, Prof.: And this is a bouncing cosmology where we assume that this game fact that starts out in a contract in phase there's a new physics, which leads you to a transition to send a big bang expansion and, in my case, this new physics, is going to be an s spring.

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Robert Brandenberger, Prof.: But it could be anything else.

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Robert Brandenberger, Prof.: and on top, is the result in space time diagram so vertical axis time horizontal axis is space Michael moving coordinates T equals zero is a bounce time.

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Robert Brandenberger, Prof.: Negative times is the face of contraction positive times is standard big bang expansion and Time runs from minus infinity plus infinity so the horizon is infinite horizon problem solved.

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Robert Brandenberger, Prof.: fluctuations emerged from sub scales at sufficiently already times so second criteria insult.

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us.

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Robert Brandenberger, Prof.: And it turns out that if you look at scales which exit the hubble radiosurgery no matter dominated traces contraction and you start with backing motivations, you will generate the skinny band spectrum.

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Robert Brandenberger, Prof.: So a third scenario and a scenario which might be more promising, from the point of view of quite a gravity is an emergent scenario where you start with some.

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Robert Brandenberger, Prof.: early phase in which we don't have the classical generativity space time structure, and I will moderate as a face of constant scale factor, and then you have a transition to standard be buying expansion, maybe phase transition.

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Robert Brandenberger, Prof.: And this gives rise to this space time diagram so time vertical axis, this is my emergent phase.

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Robert Brandenberger, Prof.: Models yes classic classical this is space again the horizon is infinite.

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Robert Brandenberger, Prof.: Again scares that we observe today start out some horrible at already times and therefore you have a potential of coming up with a successful audience scenario.

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Robert Brandenberger, Prof.: I haven't told you how you generate a skinny van spectrum of innovations, but I will come to that, at the end of the talk so bottom line is that there are several scenarios.

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Robert Brandenberger, Prof.: which you can imagine, with what you've been explained the current data, not just inflation.

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Robert Brandenberger, Prof.: So now, I remind you of the basic observable.

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Robert Brandenberger, Prof.: We can look at density perturbations or colored perturbations and we can look at the power spectrum.

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Robert Brandenberger, Prof.: And the power spectrum on a picnic for a particular wave number K gives you the means squared fluctuations of the curvature.

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Robert Brandenberger, Prof.: On a link scale K inverse that's the power spectrum and the K dependence of the power spectrum is conventionally described in this power form.

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Robert Brandenberger, Prof.: And as a scale of spectral index and an s equals one is by definition skinny about gravitational waves of the power spectrum pH of K, which is conventionally.

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Robert Brandenberger, Prof.: described in this way and so skating violence is an s equals one and T equals zero.

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Robert Brandenberger, Prof.: And we also interested in the ratio of the power spectrum of gravity waves divided by power spectrums perturbations that's the famous tensor to skate a racial or So these are basically what what we would like to compute from any quarter gravity model.

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Robert Brandenberger, Prof.: So now i'll try to deconstruct inflation, so I ran you what inflation is.

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Robert Brandenberger, Prof.: whoops i'm going much too far in my talk.

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Robert Brandenberger, Prof.: Inflation is the idea that you have a new phase of nearly exponential expansive space at some point in the universe.

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Robert Brandenberger, Prof.: And if you don't want to fine tune your parameters of the inflationary model inflation takes place at an energy scale which is rather close to the Planck scale, and it is far, far, far removed from scales where effect a few of us are well pro.

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Robert Brandenberger, Prof.: This is a timeline.

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Robert Brandenberger, Prof.: This is a illustration of how inflation takes an initially small university makes it blog.

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Robert Brandenberger, Prof.: And this is the space time scheduled on the show and based on this space time sketch, you see that inflation has lots of successes.

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Robert Brandenberger, Prof.: It renders universe locks on the genius and spacious flat.

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Robert Brandenberger, Prof.: classical matter right shifts and so matter purchasing vacuum state, and if you populate that the source of perturbations of vacuum perturbations, then you get scaled down spectrum.

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Robert Brandenberger, Prof.: And you get a small ratchet for the spectrum of density perturbations and the prediction, which has not yet been tested is a small red tilt of the spectrum of gravitational waves.

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Robert Brandenberger, Prof.: And the bouncy model that I will show you has the same features for what has been observed today but it predicts a small blue tilt of the spectrum of gravitational freedom.

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Robert Brandenberger, Prof.: So, so far, so good for inflation, but how do we obtain inflation.

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Robert Brandenberger, Prof.: Well, if we insist that space, time is describe excellent relativity, then we need matter with precious smaller than minus one third Energy density in fact close to minus energy density.

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Robert Brandenberger, Prof.: The easiest way to get at is we introduce a scale of fields, because we can get anything we want if we need to scale it feels.

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Robert Brandenberger, Prof.: The potential energy time of a scale of field has the right equation state P equals minus role.

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Robert Brandenberger, Prof.: So this is my skater field.

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Robert Brandenberger, Prof.: He has a potential energy and if the skater field is at rest up here, then we have P equals minus one.

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Robert Brandenberger, Prof.: But scale of fields have other contributions to the energy density kinetic energy and graded energy so in order to ensure that potential energy dominates the scale of your leads to be slowly rolling very slowly rolling that's why I spelt rolling with two with three l's.

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Robert Brandenberger, Prof.: So i'm quantify this the derivative of the scale of field with respect to the other scale if your potential, with the specular skater field has to be much, much smaller than one of them pump.

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Robert Brandenberger, Prof.: And if you don't want to fine tune initial conditions for your schofield the scale of your ass to roll over large distances.

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Robert Brandenberger, Prof.: So large field inflation its local attractor in initial mission space, whereas if you want to work with small field inflation, you have to tune initial conditions.

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Robert Brandenberger, Prof.: So now, I want to.

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Robert Brandenberger, Prof.: point out what i've us some problems of scale of field ribbon inflation at a level of effective your theories.

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Robert Brandenberger, Prof.: So.

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Robert Brandenberger, Prof.: The key difficulty is that inflation takes place at a scale where we should question the applicability of effective field theory, because we are very close to the quantum gravity scale or to the string scale.

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Robert Brandenberger, Prof.: So when really should ask how can we obtain inflation does inflation even make sense.

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Robert Brandenberger, Prof.: And so, one problem of inflation, which we spoke about 20 years ago is the transplanting problem and we pointed out that if inflation was only a little bit longer than it has to last, in order to be successful, that then all scales that we observe today.

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Robert Brandenberger, Prof.: In observations start out with a wavelength smaller than the Planck length at the beginning of inflation.

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Robert Brandenberger, Prof.: Now, based on this picture, two years ago my droid buffer postulated a new sense of conjecture the transplant centers of conjecture.

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Robert Brandenberger, Prof.: They said that.

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Robert Brandenberger, Prof.: Any acceptable cosmology history of the property that the Planck length at the initial time keys I it cannot evolve into a length at a later time piece of art.

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Robert Brandenberger, Prof.: So this is the initial Planck length expanded to the later time he saw it cannot become larger than the hubble radius at the time she saw So this is the transplanting sensitive conjecture and well, what are the motivations for this.

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Robert Brandenberger, Prof.: Well, I would motivated in analogy with pen roses cosmic censorship hypothesis for blackhawks.

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Robert Brandenberger, Prof.: So.

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Robert Brandenberger, Prof.: black holes with charge smaller than the mass have a singularity but for an observer outside of the black hole the singularity is hidden by a horizon.

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Robert Brandenberger, Prof.: So the bad things that go on at the singularity don't influence the observer.

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Robert Brandenberger, Prof.: However, I sent equations admits solutions where the charge equated in the mass and for works an observer far away from the black hole.

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Robert Brandenberger, Prof.: sees the singularity enhances faced with all of the problems of non Union charity which this diagram producers and so Penrose postulated the following.

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Robert Brandenberger, Prof.: He said that, although the effective field theory of general relativity allow such pathological solutions, the correct auto valid physics should prohibit them so that's Penrose.

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Robert Brandenberger, Prof.: So let's translate pen roses cosmic sense drip hypothesis to pathology.

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Robert Brandenberger, Prof.: So position space becomes momentum space, the black hole singularity becomes them transplanting modes instead of transplanting modes in the black hole horizon becomes other horizon so Penrose translated, means that the observer.

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Robert Brandenberger, Prof.: Who only has access to the nodes for wavelengths larger than the hubble horizon must be shielded from transplanting modes.

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Robert Brandenberger, Prof.: So now, why do we take the hubble horizon as the crucial landscape and the reason is that fluctuations only oscillate on sub scales, whereas they freeze out and become classical.

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Robert Brandenberger, Prof.: insuperable escapes and a very mild demand is to demand that only the classical region be insensitive to the transplant can jump so we want know transplanting molds to ever.

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Robert Brandenberger, Prof.: become squeezed and classical lies.

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Robert Brandenberger, Prof.: So I don't mind if you replace the TC by a stronger criterion, this is a very modest right here and.

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Robert Brandenberger, Prof.: there's also the non unit out you have any effect of quantum field theory and expanding universe.

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Robert Brandenberger, Prof.: In effect of quantum field theory, you have to use an automatic cut off it's a fixed physical scale in an expanding universe, you have to continuously create new modes to maintain fixed physical cut off.

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Robert Brandenberger, Prof.: And that's extreme you know, to give ideation and if we demand that this unit clarity evaluation is not visible to us observer, then we get the GCC.

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Robert Brandenberger, Prof.: Now, what does a dcc imply for inflation.

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Robert Brandenberger, Prof.: Well, so here's my space time diagram of inflation.

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Robert Brandenberger, Prof.: So this is the inflationary period.

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Robert Brandenberger, Prof.: So we demand that the Planck length, this is the plank distance the pump length at the beginning of inflation cannot grow to be larger than the hubble length at the end of inflation, if it grows to the hover links at the end of iteration then afterwards I say.

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Robert Brandenberger, Prof.: But if inflation is to be successful, then the current toggle radius has to emerge from inside of the hubble radius at the beginning of inflation inflation doesn't do the job for what it was designed.

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Robert Brandenberger, Prof.: So the transplanting sensitive contracture gives you an upper bound on the duration of inflation, whereas the demand that inflation successful gives your lower bound on the duration of inflation.

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Robert Brandenberger, Prof.: And whether these are consistent or not depends on how large, you have a radius is during inflation compared to the public, the lower the energy scale of inflation, the further away this curve is the other races from the danger zone and the easier it is to implement inflation.

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Robert Brandenberger, Prof.: Consistent with a TC so let's do the algebra.

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Robert Brandenberger, Prof.: This is the upper bound on the duration of inflation she's upstairs the beginning of integration piece of is the time of reading.

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Robert Brandenberger, Prof.: This is the lower bound demanding that the current toggle radius starts out.

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Robert Brandenberger, Prof.: smaller than the hug radius at the beginning of inflation, you mix the two together and you immediately find that the scale of inflation has to be very low compared to what we would like inflation.

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Robert Brandenberger, Prof.: And this, in particular, implies that if you stick to such inflationary models, they will result in utterly negligible aptitude primordial gravitational waves.

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Robert Brandenberger, Prof.: In contrast to what people usually see people usually say inflation produces.

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Robert Brandenberger, Prof.: A large amplitude of gravitational waves just completely wrong.

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Robert Brandenberger, Prof.: Okay, so I believe that this problem of inflation is generic to any in the context of any quantum gravity model.

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Robert Brandenberger, Prof.: Now, specifically in the context of string theory, there are some more specific problems so and.

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Robert Brandenberger, Prof.: So at the level of effective field theory there's a huge landscape of possibilities any space time dimension goes any number of fields goes any shape of the potential is okay, and if your range is like a.

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Robert Brandenberger, Prof.: super string theory is very constraining at every quantum gravity theory is going to be very constraining it's not going to allow the vast majority of.

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Robert Brandenberger, Prof.: possibilities of effective fields, only a small subset of all effectively of yours is consistent with quantum reality, the rest line, this one plan so you have your quantum gravity theory and it picks out only small habitable islands in this tremendous swamp of effective field theories.

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Robert Brandenberger, Prof.: And what are the conditions of habitable islands to stick out from the swamp.

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Robert Brandenberger, Prof.: If your habit of what it contains a scale of field.

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Robert Brandenberger, Prof.: Then, first of all, the effect of field theory is only applicable on field range is smaller than a Planck.

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Robert Brandenberger, Prof.: scale and the potential has to be either steep or sufficiently tacky on when these criteria were formulated were derived in a context of string theory.

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Robert Brandenberger, Prof.: But I believe that you should also be able to derive that same conclusions in any quantum gravity model in which you knots if you don't stick in scale of fields, by hand.

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Robert Brandenberger, Prof.: that's my claim.

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Abhay Vasant Ashtekar: rating but that's something like if I if, in fact, the scale of field came from something like I started being inflation and that particular.

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Abhay Vasant Ashtekar: hire a dedicated coupling.

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Abhay Vasant Ashtekar: I.

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Abhay Vasant Ashtekar: will not be concise language it.

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Robert Brandenberger, Prof.: will not be consistent.

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Abhay Vasant Ashtekar: No, but I want to understand your point of view about.

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Abhay Vasant Ashtekar: Whether that is not something which is scale if you put behind in fact.

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Abhay Vasant Ashtekar: Can you, you can do.

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Abhay Vasant Ashtekar: I know this is of scale.

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Robert Brandenberger, Prof.: Of this is not 14 by hand Okay, this is not put in by hand because this is an example of something that's not put in the hand and it's also it's also the an example of something that does not give you information.

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Abhay Vasant Ashtekar: No i'm talking let's get started in skin inflation inflation.

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Robert Brandenberger, Prof.: Well, but i'm not taking it.

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Robert Brandenberger, Prof.: and not allowing you to fine tune to extreme.

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Abhay Vasant Ashtekar: So you're not allowing me to find to the company.

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Abhay Vasant Ashtekar: Constantly in contact Richard.

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Abhay Vasant Ashtekar: I just want to understand.

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Abhay Vasant Ashtekar: assumptions, I mean yeah we're.

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Abhay Vasant Ashtekar: Good right.

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Abhay Vasant Ashtekar: But also, I want to say, etc assume that in fact there's a classical geometry, all the way, because it cannot be formulated otherwise, just like our project scope that juncture assumes that.

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Robert Brandenberger, Prof.: that's what So if you manage to construct the inflationary model, not on the basis of effective field theories and not sticking a scale of your by hand, then you are safe.

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Robert Brandenberger, Prof.: In our recent proposals to do that by the by good value and his collaborators and also by my colleague case of a sculptor and his colleague, so my criticism is at the level of inflation, described by effective field theory.

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Abhay Vasant Ashtekar: Good understood, so you know statements about if you find something here model quantum geometry.

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Robert Brandenberger, Prof.: No, in fact, I think that in fact the point that i'm making is that you really should go to the basis of quantum geometry and and come up with a new scenario.

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Robert Brandenberger, Prof.: But I think it will not involve integration.

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Abhay Vasant Ashtekar: No that's okay it meanwhile inflation some effective sensor it can be interpreted as like just like started writing.

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Robert Brandenberger, Prof.: I don't think so I don't think so.

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Robert Brandenberger, Prof.: I think you I think one I think one should one should look at things which.

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Robert Brandenberger, Prof.: Naturally, come from quantum gravity with out being prejudiced by wanting to get inflation.

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Abhay Vasant Ashtekar: No, no, I agree with that.

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Robert Brandenberger, Prof.: And I will show you an example.

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Abhay Vasant Ashtekar: I agree with that, I mean did you know that just go and I think we're on the same foot right you're saying.

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Robert Brandenberger, Prof.: Maybe certainly also consequences for a time cosmology pronounced skip this over.

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psingh: hey Robert it's but i'm here, can I ask you a brief question.

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psingh: yep so you I think I agree with the DC conjecture ruling out this single field inflationary models like I I see.

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Robert Brandenberger, Prof.: Nothing about single field.

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psingh: Okay, but that's what is my question, what about the What about, but maybe it's possible to have a multi field inflationary models, where you have a five four.

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psingh: plus five square kind of potential driving a different energy scales can one escape the CCC conjecturing that case I just need your thoughts.

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Robert Brandenberger, Prof.: I know it, it does not.

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Robert Brandenberger, Prof.: Okay, you cannot so you can work with to field inflation models and you will find that the constraints are slightly different, but if you have the early facing looks perturbations are generated if you have this occurring at the grand unification scale then you're doing okay.

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psingh: I have another question so in your in just like couple of slides before like I thought, like you, are very nicely motivating that high energy inflationary models like five current so on our.

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psingh: doom, but if you are low energy inflationary models, then probably inflation is compatible with PC.

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Robert Brandenberger, Prof.: Right so you're you're referring to this picture, where I sort of said that low energy state inflation means that the hubble radius becomes larger and larger and it gets easier and easier to get to get inflation to be consistent with the GCC.

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psingh: Yes, but we know that one of the problems, even for the low energy inflationary models is the problem of onset of inflation, like then.

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psingh: The probability of inflation to actually on set for low energy inflationary models is very hard, but, but then does dcc also rule out.

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psingh: Models like stravinsky inflation, which are low energy inflation I didn't understand your answer to have a like vice dubinsky inflation has an effective inflation is ruled out, but dcc when it's a low energy efficiency model.

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Robert Brandenberger, Prof.: No, no, see my my understanding of style minsky inflation is that it is a high scale inflationary model.

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psingh: But the doctors tend to the park nine units below the below the Planck scale.

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Robert Brandenberger, Prof.: No, no, it is standard the energy scale at which integration takes place unless i'm wrong.

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Abhay Vasant Ashtekar: it's the banana banana skin is not doesn't mean anything as started with his emphasis should.

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Robert Brandenberger, Prof.: Be education government as a radius which.

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Abhay Vasant Ashtekar: duck duck what color which case it just doesn't mean anything, is it started with kids and.

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Robert Brandenberger, Prof.: I don't.

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Robert Brandenberger, Prof.: Like we're talking about a.

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radius.

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Abhay Vasant Ashtekar: And we can.

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Abhay Vasant Ashtekar: We can talk about the.

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Abhay Vasant Ashtekar: The the coverage escape right which is in value.

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Robert Brandenberger, Prof.: And the other, which is 10 to the minus 12.

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Abhay Vasant Ashtekar: Times one.

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psingh: glitch exactly Thank you so it's trying to yeah so Robert like the courageous Kelly standard y minus 12 times below the five star inflation know the scales, so if starbucks inflation is a low energy inflation shouldn't it be compatible with DC.

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Robert Brandenberger, Prof.: saw that this is not my understanding of star beings conflation Ryan, as any of star beings inflation is that the hubble radius corresponds to an energy scale of 10 to 16 GB or maybe i'm wrong about that okay.

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Robert Brandenberger, Prof.: let's let's.

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Abhay Vasant Ashtekar: discuss it later.

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Abhay Vasant Ashtekar: that's it let's discuss lead, and I think we should just leave out a larger scale from those considerations are together because.

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Robert Brandenberger, Prof.: they'll have a radio.

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Abhay Vasant Ashtekar: is fine and also the scale is fine, so.

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Robert Brandenberger, Prof.: I thought that.

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Robert Brandenberger, Prof.: Is the same OK OK.

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Abhay Vasant Ashtekar: let's go.

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Robert Brandenberger, Prof.: Next.

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Robert Brandenberger, Prof.: Okay, so.

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Good.

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Robert Brandenberger, Prof.: plan so now, I want to go on to what I was asked to talk about, namely bouncing cosmologists as an alternative, and first of all I want to argue that if you try to construct a bouncing scenario based on quantum gravity, then you should try to include economic contraction.

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Robert Brandenberger, Prof.: So the aquatic scenarios a bounty cosmology with the face of very slow contraction and among all bouncing models yet chaotic scenario has distinct advantages.

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Robert Brandenberger, Prof.: Because it dilutes anisotropy see creates spatial flatness and it is an attractor in a new condition space with all the Nice features would inflationary expansion.

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Robert Brandenberger, Prof.: If you folks and we'll just look at matter the matter bounce scenario, which is something i've worked on quite a bit so matter dominated phase of contraction, then you.

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Robert Brandenberger, Prof.: And I thought it was blow up on you, you don't generate spatial flatness and you have an initial condition problem.

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Robert Brandenberger, Prof.: So this is why I will focus on the UK for Arctic scenario so yeah products and areas of phase of a slow contraction so the scale of fact as a function of time, time is negative in the contract and face it's a very small power time and in conformal time it's also very small power.

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Robert Brandenberger, Prof.: Now you can obtain a vertical traction if you use generativity plus a scale of field with a negative exponential potential.

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Robert Brandenberger, Prof.: And you see the exponent here the prefect is the exponent is scaled have to overpay so it's quite a steep exponential it's not a flat potential to see potential now negative exponential potentials arise like ubiquity ubiquitously in string theory.

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Robert Brandenberger, Prof.: Okay, so you take this potential.

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Robert Brandenberger, Prof.: And this is the equation of state parameters so w pressure divided by energy density is much bigger than one.

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Robert Brandenberger, Prof.: And this is the evolution of the scale of your time, this is the rolling gig per Article tracking trajectory and the point is that, if you look at one time the scale of your roles only a very small distance compared to the Planck length.

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Robert Brandenberger, Prof.: The potential is quite steep and so, therefore, the swamp line criteria automatically satisfied.

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Abhay Vasant Ashtekar: And they are not only putting a scale of protection behind that yeah yeah so.

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Robert Brandenberger, Prof.: that's like, but I was asked to talk about balancing cosmology said.

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Abhay Vasant Ashtekar: Okay, this is good good thank.

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You.

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Robert Brandenberger, Prof.: The most promising good.

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Robert Brandenberger, Prof.: You see.

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Robert Brandenberger, Prof.: Even that, even at that point, you could ask me very serious problems now me how do I get the bounce I can't get that with this scale of yoga and classical gravity.

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Robert Brandenberger, Prof.: Right, how does when o'kane a spectrum of almost scared about cosmological perturbations and our gravitational waves produced.

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Robert Brandenberger, Prof.: And now the new thing that insulin previous realisations we needed extra matter fields was exponential potentials to update about and to obtain the scale vast spectrum of cosmological perturbations and we essentially got no gravitational waves.

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Robert Brandenberger, Prof.: And then, what our work has shown is that with one small ingredient, which is called an s brain we get a continuous bounce.

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Robert Brandenberger, Prof.: This is not a differential bounce it's a continuous bounce we get gravitational waves with us gain advanced spectrum.

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Robert Brandenberger, Prof.: And if the brain has zero fear, then we get skin band spectrum of curvature perturbations and we get to consistency, relations between the four basic has multiple observers will try and reduce.

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Robert Brandenberger, Prof.: One which.

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Robert Brandenberger, Prof.: says that you should get a slight detail of the graduates.

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Ivan Agullo: And you say what the continuous bounces again sorry.

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Robert Brandenberger, Prof.: The skater factor is a continuous function of time, it is not differential.

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Okay.

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Robert Brandenberger, Prof.: So.

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Robert Brandenberger, Prof.: Okay now what is he yes break so.

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Robert Brandenberger, Prof.: i'll go.

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Ivan Agullo: To so called mature they were decent the bounce because he is not differential.

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Robert Brandenberger, Prof.: You will see what wait for for the next slide.

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Robert Brandenberger, Prof.: So what i'm going to argue, is that.

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Robert Brandenberger, Prof.: at low at.

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Robert Brandenberger, Prof.: Okay, we are starting with a low energy theory which has no energy degrees of freedom for example matter degrees freedoms, but then, when you reach high.

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Robert Brandenberger, Prof.: Energy scales, in particular, if you come from the point of view of string theory, they are these high energy scales other matter degrees of freedom can be excited.

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Robert Brandenberger, Prof.: And this implies.

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Robert Brandenberger, Prof.: That your point particle effects of fear fear will break down.

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Robert Brandenberger, Prof.: and ideas that once the contract universe reaches the string scale the string energy density and have to scale to find out scale.

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Robert Brandenberger, Prof.: Then, a new tower of string states becomes comparable in mass, it has to be included in the low energy effective action and we included as a new term localized on a space like hyper so we use it as a distribution so so here's what we here's what we do we take.

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Robert Brandenberger, Prof.: US nine and we add to that which.

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Robert Brandenberger, Prof.: is low on.

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Robert Brandenberger, Prof.: Space like surface of this limiting.

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Robert Brandenberger, Prof.: and

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psingh: My phone.

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Robert Brandenberger, Prof.: Okay.

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Is it still.

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Jorge Pullin: No it's okay it's.

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Robert Brandenberger, Prof.: Okay.

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Robert Brandenberger, Prof.: I apologize, so this is our modified low energy effective fear theory and now what we do to get your question Yvonne is that we match general relativity solutions across of this s brain.

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Robert Brandenberger, Prof.: By the generalization of the Israel matching conditions, the generalization to space like surfaces, which were derived by WHO and mcanuff.

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Robert Brandenberger, Prof.: So.

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Abhay Vasant Ashtekar: Is this really a systematic proof that, in fact, there is a lawyer energy production was using this action from some entity or Is this something that is block plausibility argument that you will get so much like.

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Robert Brandenberger, Prof.: This is not rigorous.

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Robert Brandenberger, Prof.: From string theory, but the but it's a it's a possibility argument.

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Robert Brandenberger, Prof.: Okay now what So what is definite is at once you reach the time House will be once strings, then you low energy effective action will break down.

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Robert Brandenberger, Prof.: And we are trying to save it by adding this string motivated term, and I will argue that this mediates the transition from contraction to expansion and then in the future the sprint the low energy effective action is justified again so it's a self consistency argument, but not necessarily.

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psingh: A robot like a quick question so can one have this continuous solution in presence of a masterpiece and the contracting branch.

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psingh: Yes, okay in the you mean like in the bank even or banking nine kind of a scenario.

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Robert Brandenberger, Prof.: He has no problem with that we haven't bought it out explicitly okay.

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psingh: And what will approximately what is the magnitude of the creation of State at the bounce like is it much greater than one.

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Robert Brandenberger, Prof.: Okay i'll come to that okay Well, this is exactly this slot you see this space psychometric test vanishing component of kimmy new political to the surface.

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Robert Brandenberger, Prof.: So the energy density is zero but it's a relativist are tricky it has negative pressure positive tension, so this is the answer to your question.

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Robert Brandenberger, Prof.: So obviously you get a violation of dominant energy condition and therefore it is possible to obtain a non singular cosmology, it is possible to read about cosmology.

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Robert Brandenberger, Prof.: Specifically, these are the matching conditions.

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Robert Brandenberger, Prof.: there's a continuity of the induced metric and the trump in the explicit curvature which is given by the attention of the brain, and this is the drunk of the extrinsic curvature and you see that if we had a string sale.

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Robert Brandenberger, Prof.: magnitude of teemu, then we can get a trump from contraction to expansion.

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Robert Brandenberger, Prof.: i'll ask you to accept that.

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Robert Brandenberger, Prof.: So this is, this is the key point.

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Robert Brandenberger, Prof.: So now.

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Robert Brandenberger, Prof.: Maybe there are some maybe in your favorite quantum value models there's something similar a similar argument that you can make.

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Robert Brandenberger, Prof.: You will replace yesterday and buy something else.

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Robert Brandenberger, Prof.: Okay now i'm ready a bit short of time and I will just show you how you can connect this specific example of a bouncing cosmology with predictions for two patients.

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Robert Brandenberger, Prof.: So let's look at gravitational waves htc altitude of the gravitational waves.

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Robert Brandenberger, Prof.: The rescaling gravity waves amplitude obeys the standard equation emotional.

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Robert Brandenberger, Prof.: And you find that if you just look at the contract in phase, since this time is very small, the initial vacuum spectrum remains that.

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Robert Brandenberger, Prof.: So during the face of erotic contraction you don't generate any first bubble bath use the waves on.

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Robert Brandenberger, Prof.: Now, in terms of.

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Robert Brandenberger, Prof.: covert operations perturbations well yeah different variables that you can use to describe covert operations, there is the.

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Robert Brandenberger, Prof.: Variable that appears in metric in longitudinal gate the so called body valuable and then there's a sasaki mcconnell variable.

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Robert Brandenberger, Prof.: And if you look at the society of America, you find the same equation as gravitational waves and you find that during contraction.

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Robert Brandenberger, Prof.: Be sasaki moving off valuable does not get the scale down spectrum.

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Robert Brandenberger, Prof.: However, if you work in terms of audience valuable.

323
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Robert Brandenberger, Prof.: Then, or the risk involved, then you find a skating spectrum, with a slight retold at the end of the face of contractions.

324
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Robert Brandenberger, Prof.: So, the key question is what variable passes through the bounce continuously.

325
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Robert Brandenberger, Prof.: Any previous work where we modeled the bounce using a sick though energy effect of your theory.

326
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Robert Brandenberger, Prof.: which was different we are the scare factor was good French a differentiable function of time, we found that it is usually V, which is continuance and by the bronx.

327
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Robert Brandenberger, Prof.: However, as pointed out by Dora and venues rather generically if you have a matching surface.

328
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Robert Brandenberger, Prof.: Across once you connect contraction to expansion, then generically.

329
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Robert Brandenberger, Prof.: escape vast spectrum of five of the curvature productions after the month, so we look this all out in order so we found the equation in Boston for the gravity waves in the presence of this spring.

330
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Robert Brandenberger, Prof.: And this gives you a nice equation of motion with the ground patients for distribution source, you can do a book oh you both know mixing analysis.

331
00:44:43,350 --> 00:45:02,910
Robert Brandenberger, Prof.: find the how the proficiency of the two modes in the contract interface or related to the coefficients of the promoting the expanding first bottom line is you find escape from of gravity waves, with his eyes blue till after the bad prediction from this new actor model.

332
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Robert Brandenberger, Prof.: nation which produces typically a registered.

333
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Ivan Agullo: Can I ask something yeah yeah because we just mentioned this global evoke transformation, it is, it is know that whenever this key factor is not backing half for at least a second derivative says most you have infinite particle creation.

334
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Ivan Agullo: So do you see the problem here yeah.

335
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Robert Brandenberger, Prof.: You see, that you see that here.

336
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Robert Brandenberger, Prof.: Yes, you need an infrared cut off.

337
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Robert Brandenberger, Prof.: Absolutely absolutely right.

338
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Ivan Agullo: But it's not always a UV issue so.

339
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Robert Brandenberger, Prof.: Now it's an infrared issue.

340
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Abhay Vasant Ashtekar: it's a garbage it is blowing up so that would I thought that could also be an ultra wide issue.

341
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Robert Brandenberger, Prof.: I mean.

342
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Abhay Vasant Ashtekar: I think it isn't really sure I agree with that, but there's also another one.

343
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Robert Brandenberger, Prof.: Right, but we also an automatic cut off so.

344
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Abhay Vasant Ashtekar: Are y'all but But then what isn't.

345
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Robert Brandenberger, Prof.: But, again, I think the thing that you're pointing out.

346
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Robert Brandenberger, Prof.: Yvonne is the key here there's an there's something that those are in the infrared.

347
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Ivan Agullo: and also in the UV because if you integrate the tricky because.

348
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Robert Brandenberger, Prof.: This this.

349
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Robert Brandenberger, Prof.: Good we can't.

350
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Robert Brandenberger, Prof.: feel it.

351
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Robert Brandenberger, Prof.: We can't go to below the strings, otherwise we are so we can do affect the theory of the fluctuations on the.

352
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Robert Brandenberger, Prof.: scale where the background brixton okay.

353
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Robert Brandenberger, Prof.: So there's an automatic.

354
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Robert Brandenberger, Prof.: thing which is new year's is infrared issue.

355
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Abhay Vasant Ashtekar: right but, but then Robert I mean so then it's really not coming I mean what if one is going to put up cut offs on.

356
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Abhay Vasant Ashtekar: Effective fealty It is then there's no transplant can problem, to begin with.

357
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Abhay Vasant Ashtekar: So I don't understand the.

358
00:46:59,640 --> 00:47:04,020
Robert Brandenberger, Prof.: philosophy here well let's go back to let's go back to what I said here.

359
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Robert Brandenberger, Prof.: Okay.

360
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Robert Brandenberger, Prof.: So balancing mobs are consistent with the TC as long as the energy scale is lower than a plum scale now, we do not want to model any we can.

361
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Robert Brandenberger, Prof.: So if we do calculations, in the context of an effect that we have here it doesn't make sense to study modes with a wavelength smaller, then the length design.

362
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Robert Brandenberger, Prof.: pointed out of the GCC and the point is that observations or never sensitive to notes.

363
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Abhay Vasant Ashtekar: Okay, so.

364
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From this.

365
00:47:53,820 --> 00:48:04,620
Abhay Vasant Ashtekar: You you would not have objection about putting a Planck scale cut off island in the usual infecting filter isn't saying that there is not pants banking problem if I were to apply your logic to the.

366
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Robert Brandenberger, Prof.: Indian context in context of inflation there's an absolute problem, because if inflation us too long, then scales practice you be cut off become macroscopic that's a problem that's an annuity.

367
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Abhay Vasant Ashtekar: That all is going to be non you gotta get you gotta cut off.

368
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Robert Brandenberger, Prof.: yeah, but I wanted, I want the non utility hayden from from the cosmological absorb.

369
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Robert Brandenberger, Prof.: and upset in that case bouncing cosmologists any merchant commodities and six.

370
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Robert Brandenberger, Prof.: Whereas high inflation is not safe.

371
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Robert Brandenberger, Prof.: it's absolutely.

372
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Abhay Vasant Ashtekar: Okay, so in terms of fundamental physics, that there is not unique added your mind, so long as that non unit Alec is not seen by some observer then it's okay that's what you said.

373
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Robert Brandenberger, Prof.: No that's not what i'm saying, but I want to have to discuss this is, this is the reference.

374
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Robert Brandenberger, Prof.: You see, the Nice theory this theory which are just spoke about is the non unit, it has a non unitary problem.

375
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Abhay Vasant Ashtekar: mm hmm.

376
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Robert Brandenberger, Prof.: But this non unit that problem does not influence observation that we make.

377
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Robert Brandenberger, Prof.: Okay.

378
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Robert Brandenberger, Prof.: Good now it is almost 10 o'clock so I get stopped late because of the problems, but how How long do you want me to speak for.

379
00:49:34,500 --> 00:49:35,550
Jorge Pullin: Just good going for a while.

380
00:49:37,080 --> 00:49:38,220
Robert Brandenberger, Prof.: My cut off is.

381
00:49:39,900 --> 00:49:43,500
Robert Brandenberger, Prof.: 925 year time disappeared for my second class.

382
00:49:44,790 --> 00:49:47,010
Robert Brandenberger, Prof.: Okay, so good.

383
00:49:48,330 --> 00:49:48,810
Robert Brandenberger, Prof.: So.

384
00:49:53,370 --> 00:49:54,090
Robert Brandenberger, Prof.: So let me.

385
00:49:56,100 --> 00:49:56,220
psingh: What.

386
00:49:56,340 --> 00:50:08,670
Robert Brandenberger, Prof.: happened for SP EC for roles is gravity waves and now also just tell you that the cosmological perturbations obtain sky and spectrum, and this is what I skipped and.

387
00:50:09,270 --> 00:50:10,020
Robert Brandenberger, Prof.: We obtain.

388
00:50:10,680 --> 00:50:26,940
Robert Brandenberger, Prof.: Expressions for the power spectrum of color perturbations we obtain expressions of our spectrum of gravitational waves and we find that a predicted louisville of the gravitational waves equally magnitude faster predicted red tail.

389
00:50:28,050 --> 00:50:37,170
Robert Brandenberger, Prof.: Of the coverage of innovations, so we get consistency relations for cosmological observers, we also get a prediction for the temperature scale aeration.

390
00:50:38,370 --> 00:50:44,190
Robert Brandenberger, Prof.: So again, this is an example, this espenak versus it's an example of a bouncing cosmology.

391
00:50:45,240 --> 00:50:52,710
Robert Brandenberger, Prof.: which makes predictions for alterations with what she can be distinguished from inflation and this model has a.

392
00:50:53,760 --> 00:51:03,120
Robert Brandenberger, Prof.: It has a non utilitarian problem that's our be stressed, but this narnia attack, the problem is hidden from the chronological observers.

393
00:51:04,500 --> 00:51:06,150
Robert Brandenberger, Prof.: So out.

394
00:51:07,710 --> 00:51:14,670
Robert Brandenberger, Prof.: So this was bouncing cosmology and actually I am I prefer emergent cosmology so.

395
00:51:16,320 --> 00:51:17,160
Robert Brandenberger, Prof.: that's what a lot of.

396
00:51:17,880 --> 00:51:21,210
psingh: Road, can I ask a question on this planet process before we move on.

397
00:51:21,690 --> 00:51:31,440
psingh: Okay, so we know very well that in the standard aquatic scenarios, there is a problem of obtaining scale invading perturbations because the equation of state is much larger than what.

398
00:51:32,040 --> 00:51:34,320
psingh: Then you can introduce a matter of bound scenario.

399
00:51:34,680 --> 00:51:40,200
psingh: And we know the duality from the contracting branch with the matter equation of state leads to scale it variance spectrum.

400
00:51:41,370 --> 00:51:43,170
Robert Brandenberger, Prof.: So it's not the way that i'm going.

401
00:51:44,220 --> 00:51:54,150
Robert Brandenberger, Prof.: To use the fact that the that the moon upsets hockey variable has a non skating around spectrum at the end of a contract interface.

402
00:51:54,540 --> 00:52:02,520
Robert Brandenberger, Prof.: Yes, that's the final result it's also the same standard result is that the body variable has a skating band spectrum at the end of a contract fates.

403
00:52:03,420 --> 00:52:03,810
psingh: In the.

404
00:52:04,230 --> 00:52:09,480
Robert Brandenberger, Prof.: equation of state, yes, India depression fleet that is well known, since the original.

405
00:52:11,520 --> 00:52:11,880
Robert Brandenberger, Prof.: Yes.

406
00:52:12,060 --> 00:52:15,390
Robert Brandenberger, Prof.: And you can read read up on that in this durable and each each paper.

407
00:52:15,930 --> 00:52:16,170
Yes.

408
00:52:17,910 --> 00:52:22,710
psingh: But that was relevant question be that what gauging variant we work with and.

409
00:52:23,910 --> 00:52:26,310
psingh: it's tied to some gauge fixing conditions.

410
00:52:26,370 --> 00:52:35,430
Robert Brandenberger, Prof.: nope gauging that's any physical valuable is gauging bound, so the question is really works very passes through the sprain bouncing a continuous way.

411
00:52:36,480 --> 00:52:38,250
Robert Brandenberger, Prof.: This is a question that determines the answer.

412
00:52:40,050 --> 00:52:44,520
Robert Brandenberger, Prof.: And the answer is determined by the building and will kind of matching conditions.

413
00:52:45,750 --> 00:52:46,140
psingh: Okay.

414
00:52:46,770 --> 00:52:49,230
Robert Brandenberger, Prof.: We, we do not have to modify the creation of state.

415
00:52:49,320 --> 00:53:03,150
Robert Brandenberger, Prof.: Just this spring bounce translates it says that the movement of society variable jumps during the bounce where's the body variable, which is the one people used to work with all the time that is continuous.

416
00:53:05,670 --> 00:53:06,210
psingh: Okay, thanks.

417
00:53:06,270 --> 00:53:09,510
Robert Brandenberger, Prof.: For that sort of the result of all paper.

418
00:53:10,920 --> 00:53:12,330
Robert Brandenberger, Prof.: And that's that's an important question.

419
00:53:16,020 --> 00:53:16,350
Robert Brandenberger, Prof.: OK.

420
00:53:18,120 --> 00:53:18,450
Robert Brandenberger, Prof.: So.

421
00:53:20,610 --> 00:53:22,200
Robert Brandenberger, Prof.: Now let me just see.

422
00:53:24,930 --> 00:53:31,620
Robert Brandenberger, Prof.: I don't want to go on too long, so let me jump directly to this new work.

423
00:53:32,970 --> 00:53:34,410
Robert Brandenberger, Prof.: So now.

424
00:53:35,430 --> 00:53:36,900
Robert Brandenberger, Prof.: Any talk this is.

425
00:53:38,340 --> 00:53:46,320
Robert Brandenberger, Prof.: Something which Vice COPs is supposed to have said, any talk is supposed to end with something which not even the speaker understands.

426
00:53:47,460 --> 00:53:54,690
Robert Brandenberger, Prof.: And so, this is how i'm ending the talk i'm ending the talk with a part which I don't really understand myself.

427
00:53:56,760 --> 00:54:04,680
Robert Brandenberger, Prof.: well enough, but it is an attempt to construct a non unit a a unitary cosmology.

428
00:54:06,000 --> 00:54:12,540
Robert Brandenberger, Prof.: It is an attempt to construct a not just a cosmology but to get emerging space and time.

429
00:54:13,680 --> 00:54:20,400
Robert Brandenberger, Prof.: So the goal is to get immersed in space emergent time and emergent cosmology or universe, because miles.

430
00:54:21,480 --> 00:54:22,560
Robert Brandenberger, Prof.: From the matrix model.

431
00:54:23,670 --> 00:54:39,840
Robert Brandenberger, Prof.: So we start with the BF SS matrix model, now the bfs matrix model banks vicious shanker susskind is a quantum mechanical model of n cross and permission matrices so there's no space there no single out is.

432
00:54:41,790 --> 00:54:43,320
Robert Brandenberger, Prof.: Is unitary.

433
00:54:44,790 --> 00:54:47,880
Robert Brandenberger, Prof.: OK, so now, this is a garage in of the model.

434
00:54:49,500 --> 00:54:58,230
Robert Brandenberger, Prof.: So these exercise or nine and by an omission matrices and there's another attempt matrix in the current derivative here.

435
00:55:00,420 --> 00:55:00,840
Robert Brandenberger, Prof.: Now.

436
00:55:02,190 --> 00:55:05,430
Robert Brandenberger, Prof.: We look at this matrix model at a high temperature.

437
00:55:07,530 --> 00:55:12,870
Robert Brandenberger, Prof.: And then we realize that, in this case the eigenvalues of a not.

438
00:55:14,580 --> 00:55:30,660
Robert Brandenberger, Prof.: So Okay, one of these matrices can be diagnosed with analyze a not but it's not, which is the matrix of psm cover and render and the I evaluate a not we call them emerge.

439
00:55:32,040 --> 00:55:33,510
Robert Brandenberger, Prof.: In the end, going to infinity them.

440
00:55:34,680 --> 00:55:51,000
Robert Brandenberger, Prof.: and working in the basis, in which a not is diagnose the X I matrices become block diagram that's a result of studies of this matrix model and these locks these X is become immersed in space in the end, going to infinity.

441
00:55:52,830 --> 00:56:04,950
Robert Brandenberger, Prof.: OK, so the way to visualize this is, we have this zero matrix which we die guys, and these are alpha once they become the time.

442
00:56:06,330 --> 00:56:19,050
Robert Brandenberger, Prof.: that's that's a time valuable it's discrete for capital N, find it becomes continuous when and goes to infinity and the extent of these blocks that becomes dimensional space.

443
00:56:21,180 --> 00:56:34,350
Robert Brandenberger, Prof.: So now, this matrix liberation has an eaten up new symbol contained in it and therefore in the capital N going to infinity limit we get local orange.

444
00:56:37,530 --> 00:56:43,920
Robert Brandenberger, Prof.: Now what we've done is we've computed thermal correlation functions in this matrix model.

445
00:56:45,030 --> 00:56:57,330
Robert Brandenberger, Prof.: So we have the partition function of this matrix model we can compute all kinds of correlation functions and what he's caught and then these correlation functions, we can relate them to.

446
00:56:59,250 --> 00:57:03,690
Robert Brandenberger, Prof.: To density perturbations and gravitational waves like we did in spring as cosmology.

447
00:57:05,190 --> 00:57:05,580
Robert Brandenberger, Prof.: and

448
00:57:05,910 --> 00:57:07,440
Robert Brandenberger, Prof.: We obtained the same results that we.

449
00:57:07,440 --> 00:57:13,590
Robert Brandenberger, Prof.: got in string gas cosmology, so this is a proposal of a model.

450
00:57:15,030 --> 00:57:22,050
Robert Brandenberger, Prof.: Which is good at Terry work with what we can get emerged in space emergent time.

451
00:57:23,460 --> 00:57:29,970
Robert Brandenberger, Prof.: And an inverted or universe cosmology which is not inflation, and so I would like to invite.

452
00:57:31,620 --> 00:57:42,210
Robert Brandenberger, Prof.: Those of you working on different quantum gravity models to try to see if you can implement the same thing and so again, the crucial thing is that you look at your quantum gravity phase.

453
00:57:43,620 --> 00:57:53,790
Robert Brandenberger, Prof.: You have a partition function of quantum gravity and then given this partition function of quantum gravity, then what you do is you compute coalition functions.

454
00:57:55,020 --> 00:58:07,230
Robert Brandenberger, Prof.: So, and I will end with showing these correlation functions, so we what we want to do is, we want to compute on infrared scales, the curvature perturbations and the gravitational waves.

455
00:58:08,670 --> 00:58:21,930
Robert Brandenberger, Prof.: And the College of renovations are given by the Energy density fluctuations, the gravitational waves are given by these after confessor perturbations given your quantum gravity partition function, you can compute these quantities.

456
00:58:23,250 --> 00:58:28,020
Robert Brandenberger, Prof.: And then, given these qualities, you can compute the curvature perturbations and the gravitational waves.

457
00:58:29,040 --> 00:58:46,530
Robert Brandenberger, Prof.: This is what we did in 2006 2007 in the context of string as cosmology this is now Yuri refer patella myself, and this is what we've now repeated implemented in terms of this bfs matrix model.

458
00:58:47,940 --> 00:59:04,680
Robert Brandenberger, Prof.: So I would like to conclude now, so we have lots of data about the cosmos and much more data as expected soon and the cosmological data can only be explained using new fundamental physics operating in the very universe, hopefully quantum gravity.

459
00:59:06,000 --> 00:59:20,730
Robert Brandenberger, Prof.: So the current paradigm is effective theory description of our universe, because i'm argue based on cosmological inflation and there are alternatives to cosmological inflation.

460
00:59:21,930 --> 00:59:29,310
Robert Brandenberger, Prof.: that's a robust statement, so I think these points in my conclusions are non controversial.

461
00:59:31,410 --> 00:59:37,560
Robert Brandenberger, Prof.: Now let me move on to the controversial conclusions that I, hopefully, will have persuaded, some of you are.

462
00:59:38,760 --> 00:59:44,970
Robert Brandenberger, Prof.: So the effect of field theory now analysis of it suffers from conceptual problems.

463
00:59:46,260 --> 00:59:57,210
Robert Brandenberger, Prof.: And I think one should go beyond and effective feel for your analysis we really want to describe the value of the universe, I think, in this audience, this is going to be completely non controversial.

464
00:59:58,380 --> 01:00:07,050
Robert Brandenberger, Prof.: And if you want to stick to a bouncing cosmology, then I think that you need to look into realizations of the erotic fantasy cosmology.

465
01:00:08,610 --> 01:00:12,330
Robert Brandenberger, Prof.: So again, this does not solve the underlying utility problem.

466
01:00:13,710 --> 01:00:14,520
Robert Brandenberger, Prof.: So I picked up.

467
01:00:15,840 --> 01:00:16,380
Robert Brandenberger, Prof.: and

468
01:00:18,780 --> 01:00:32,280
Robert Brandenberger, Prof.: Good so, but given such a scenario which is motivated by quantum gravity, we can make predictions, we can connect quantum gravity with observations and we can make predictions for future observations.

469
01:00:33,540 --> 01:00:50,280
Robert Brandenberger, Prof.: And finally, the last point is the point that even, I would like to be more convinced of, namely that we can take a matrix model which is proposed as an entrepreneur definition of string theory and we can get emergent space time and early universe cosmology from it.

470
01:00:51,420 --> 01:00:53,490
Robert Brandenberger, Prof.: So thanks for listening thanks for the questions.

471
01:01:03,270 --> 01:01:09,270
Jorge Pullin: Here we have a few minutes for questions because Robert has a good teacher has his hand raised hey.

472
01:01:09,780 --> 01:01:13,920
Ivan Agullo: Thank you for for the dark it was it was quite very, very nice and and.

473
01:01:15,510 --> 01:01:35,760
Ivan Agullo: So, so one one key point key argument in your whole presentation was this dcc conjecture this transparency and conjecture and I never understood it so i'm going to ask to see if I can get more clarity, a you know because it's a conjecture, which involves time depending cat off.

474
01:01:37,020 --> 01:01:38,400
Robert Brandenberger, Prof.: conjecture, which you see how.

475
01:01:38,940 --> 01:01:49,440
Ivan Agullo: Right, so my problem is that in this room, I mean it's physical or mathematical physical, because in this room, I see wavelength that are coming from France banking modes in the best.

476
01:01:49,860 --> 01:01:50,580
Robert Brandenberger, Prof.: know we do have.

477
01:01:50,760 --> 01:01:51,210
Ivan Agullo: anything.

478
01:01:52,110 --> 01:01:53,910
Robert Brandenberger, Prof.: wrong, we do not, and the.

479
01:01:54,180 --> 01:02:02,070
Ivan Agullo: And and and also mathematical because we know that, then in fact the field theories, with a time depending cut off, you know.

480
01:02:02,940 --> 01:02:14,400
Ivan Agullo: Energy momentum is not commercially conserve you cannot reproduce anomalies like kinda anomalies conformal anomalies which play a key role in physics.

481
01:02:14,790 --> 01:02:22,650
Ivan Agullo: And you know and and a whole list of things, and so I don't understand both Maybe you can help me understanding, first of all, why.

482
01:02:23,220 --> 01:02:35,010
Ivan Agullo: This this length is not coming from transplant in physics, if I go far enough to the past or this or this or this or this and also what happens with the mathematical problems that that.

483
01:02:36,240 --> 01:02:37,680
Ivan Agullo: These sorts of theories.

484
01:02:37,830 --> 01:02:39,300
Robert Brandenberger, Prof.: Okay, so.

485
01:02:40,440 --> 01:02:43,800
Robert Brandenberger, Prof.: You see, instead of big bang cosmology we have.

486
01:02:45,450 --> 01:02:58,980
Robert Brandenberger, Prof.: We do have modes, which were initially transplanting which would become larger, but the physics, that we observe is let's say on scales, which are many orders of magnitude larger then.

487
01:02:59,490 --> 01:03:08,490
Robert Brandenberger, Prof.: Then the Planck length and what happens is that 30 patients on these skills are highly nonlinear and they are influenced by things trickling down from lot of webex.

488
01:03:11,670 --> 01:03:16,980
Ivan Agullo: Right, but I was mentioning that, in this room, you know if I take you know 10 centimeters and I go to the.

489
01:03:17,430 --> 01:03:18,390
Robert Brandenberger, Prof.: 10 centimeters here.

490
01:03:19,020 --> 01:03:19,440
Okay.

491
01:03:20,850 --> 01:03:27,090
Ivan Agullo: And why there is not a problem in that, and the reason because mobile is you know in larger scales, that is what I don't understand.

492
01:03:27,570 --> 01:03:32,100
Robert Brandenberger, Prof.: The problem come so our galaxy is not expanding.

493
01:03:33,150 --> 01:03:36,510
Robert Brandenberger, Prof.: So therefore there is no problem, the wavelengths are not being stretched.

494
01:03:44,490 --> 01:03:48,360
Ivan Agullo: But I mean that is because of the gravitational potential of the galaxy but that short.

495
01:03:48,360 --> 01:03:57,630
Ivan Agullo: distances gravitational potential doesn't play any role, so I don't think that that document can be used for you know wavelengths of order of centimeters today and.

496
01:03:59,700 --> 01:04:02,520
Robert Brandenberger, Prof.: Whenever we do experiments inside of our Alex.

497
01:04:12,300 --> 01:04:19,470
Robert Brandenberger, Prof.: So simply when we do experiments, we are never sensitive two modes, which in the universe had a wavelength smaller than the content.

498
01:04:24,120 --> 01:04:29,430
Ivan Agullo: I don't know if I fully agree with that, but what about the other issues that that that you know this.

499
01:04:30,840 --> 01:04:33,810
Ivan Agullo: Non conservation of non Canadian conservation of.

500
01:04:33,810 --> 01:04:36,270
Ivan Agullo: Energy dense or and anomalies, etc.

501
01:04:36,660 --> 01:04:39,750
Robert Brandenberger, Prof.: Why this is essentially elaborating on this point.

502
01:04:42,030 --> 01:04:45,600
Robert Brandenberger, Prof.: effect of quantum field theory that in an expanding universe has problems.

503
01:04:47,400 --> 01:04:48,990
Robert Brandenberger, Prof.: More problems in I mentioned here.

504
01:04:51,900 --> 01:04:54,030
Robert Brandenberger, Prof.: So I, I completely agree with that.

505
01:04:57,330 --> 01:04:58,590
Abhay Vasant Ashtekar: wow those problems and.

506
01:05:00,900 --> 01:05:09,420
Abhay Vasant Ashtekar: Why why, why is it okay to ignore those problems but focus on some other problems, and I think not understanding the viewpoints, so my take I think that's the problem.

507
01:05:11,550 --> 01:05:12,120
Robert Brandenberger, Prof.: When if we don't.

508
01:05:12,870 --> 01:05:13,980
Abhay Vasant Ashtekar: know what it problems also.

509
01:05:15,720 --> 01:05:18,330
Robert Brandenberger, Prof.: Yes, but, but if i'm a cosmologist.

510
01:05:19,500 --> 01:05:27,000
Robert Brandenberger, Prof.: And I want, I want to make sure that the calculations, that I do are safe from is automatic from I see.

511
01:05:27,120 --> 01:05:38,640
Abhay Vasant Ashtekar: So you don't care about there being coherence, the whole description about, in other words, what we do cosmology one way and we do laboratory physics another way and should we not have the same kind of theory.

512
01:05:39,630 --> 01:05:40,680
Robert Brandenberger, Prof.: It should all fit together.

513
01:05:42,000 --> 01:05:50,580
Robert Brandenberger, Prof.: But we don't have we got any it possibly it could all fit together once we have, once we have a unified quantum theory of all forces.

514
01:05:52,140 --> 01:05:53,250
Robert Brandenberger, Prof.: But i'm not that ambitious.

515
01:05:57,270 --> 01:05:59,760
psingh: robot, can I ask a question which I asked earlier.

516
01:06:00,540 --> 01:06:12,000
psingh: So I just need to know your viewpoint, so in past like you have motivated that well the one way to save the aquatic models which for of Stein had an Iraq war to introduce the matter bounce also.

517
01:06:12,330 --> 01:06:18,330
psingh: And you had very nicely shown that if you had metal band scenarios and certain bouncing universes, then you will.

518
01:06:18,810 --> 01:06:27,420
psingh: solve the skill invariance problem, as well as a nice groupie problem now you know the espionage act process is slightly different idea.

519
01:06:27,870 --> 01:06:35,700
psingh: Bear you don't have matter in it and you are working with a body and potential and then you show that you can still operate at scale in Marion spectrum of fluctuations, but.

520
01:06:35,910 --> 01:06:38,670
Robert Brandenberger, Prof.: Actually, and I can interrupt here because I think this is not.

521
01:06:39,720 --> 01:06:45,570
Robert Brandenberger, Prof.: This is not what I so bouncing the mad about scenario has an eyesore to be problem.

522
01:06:46,770 --> 01:06:56,490
psingh: Yes, unless you unless you yes by itself, it has, but if you have a process, plus metal bands, then one can probably try to construct a model which doesn't Have a nice appropriate problem.

523
01:06:56,640 --> 01:06:57,900
Robert Brandenberger, Prof.: yeah, but I think that would be.

524
01:06:59,190 --> 01:07:00,960
psingh: Very difficult I agree yeah.

525
01:07:02,010 --> 01:07:02,640
Robert Brandenberger, Prof.: So do what.

526
01:07:02,760 --> 01:07:09,510
Robert Brandenberger, Prof.: You want to matter bounce early on and then followed by X per Article interaction which dilutes the anasazi please.

527
01:07:10,380 --> 01:07:18,900
psingh: yeah so my question would be like can't find a combined somehow the matter bound scenario, with a screening process to have the best of both worlds.

528
01:07:20,880 --> 01:07:23,760
Robert Brandenberger, Prof.: Yes, you could you can do that definitely.

529
01:07:25,230 --> 01:07:25,710
Robert Brandenberger, Prof.: and

530
01:07:28,860 --> 01:07:42,840
Robert Brandenberger, Prof.: Yes, so the answer your question is yes, you can combine that I was like myself prefer to talk about just simple scenarios, where you only have one ingredient doesn't mean that you can't combine sorry, thank you.

531
01:07:44,370 --> 01:07:45,390
Jorge Pullin: You have your hand up.

532
01:07:46,890 --> 01:07:56,250
Suddhasattwa Brahma: A crank so maybe, just a quick comment to advance question also the CCC there's the other evidence is, if you start with string theory, for instance.

533
01:07:56,670 --> 01:08:06,270
Suddhasattwa Brahma: Which which need you, for accelerating space times to this kind of time cut off for an upper limit of an absolute in space time because it is it or something like this.

534
01:08:06,840 --> 01:08:10,140
Suddhasattwa Brahma: So there are other reasons and also I didn't quite follow your.

535
01:08:10,650 --> 01:08:22,980
Suddhasattwa Brahma: Your question events or maybe I ought to just clarify your question because before flat space time it's perfectly fine to have some usually cut off, and if you integrate out more than they stay integrated out that that we know.

536
01:08:23,400 --> 01:08:32,250
Suddhasattwa Brahma: But the problem here is that for an accelerating space time modes, which will, which you can just integrate out as, as you pointed out, for time dependent with spaces.

537
01:08:32,610 --> 01:08:39,240
Suddhasattwa Brahma: So that I think is the crucial difference right like if you just consider flat space time and you integrate out all transportation modes.

538
01:08:39,660 --> 01:08:49,080
Suddhasattwa Brahma: Then, and you don't start with translation wants to start with, in some experiment, then it wouldn't end up with with those but that's not the case in session.

539
01:08:49,800 --> 01:09:02,430
Ivan Agullo: Right, thank you, thank you for their for becoming so My point is that even invalids facetime if you pull that off, you cannot recover, for instance, the title anomaly, who has been used in particle physics displaying the decay of the of the.

540
01:09:02,460 --> 01:09:06,270
Suddhasattwa Brahma: moodle right right yeah that that second part, I completely agree, I was just like.

541
01:09:06,330 --> 01:09:09,030
Suddhasattwa Brahma: For the first because you're saying that you can have like things from.

542
01:09:09,600 --> 01:09:24,540
Suddhasattwa Brahma: planking sub tanking like regimes my My point is that if you if you are looking at any laboratory experiment and you, you do not start with particles on super transparent and scales, then you wouldn't end up with those but he seems to be.

543
01:09:26,430 --> 01:09:28,920
Suddhasattwa Brahma: Thank thanks for the clarification is he.

544
01:09:29,400 --> 01:09:30,210
Jorge Pullin: has his hand up.

545
01:09:30,660 --> 01:09:35,190
Abhay Vasant Ashtekar: yeah, I just wanted to clarify one thing, because to both to Robert and to everybody else.

546
01:09:35,610 --> 01:09:42,330
Abhay Vasant Ashtekar: That, unfortunately, you know in Luke quantum gravity, we also use the word effective equations and effective something.

547
01:09:42,690 --> 01:09:56,790
Abhay Vasant Ashtekar: I just want to say it has nothing to do with the way that the effective word effective is used in field theories, you know, like integrating out some modes as the door just saying, or anything else, this effective is really using the English language sense of the world.

548
01:09:57,870 --> 01:10:02,400
Abhay Vasant Ashtekar: And what what he's saying is that the content collected geometry.

549
01:10:03,660 --> 01:10:08,340
Abhay Vasant Ashtekar: has some effects and the leading or the behavior of that can be.

550
01:10:09,510 --> 01:10:13,440
Abhay Vasant Ashtekar: absorbed into corrections to einstein's.

551
01:10:14,700 --> 01:10:20,280
Abhay Vasant Ashtekar: Due to the space time metric given by the Einstein theory, and that is what we call effective.

552
01:10:21,000 --> 01:10:28,740
Abhay Vasant Ashtekar: And so it really so I just want to say that that can be always offer a confusion between the I just identifying the two senses of effective.

553
01:10:29,220 --> 01:10:36,660
Abhay Vasant Ashtekar: And I think the way the way in which we are using the term effective is completely compatible with what Robert was saying, I just wanted to emphasize that.

554
01:10:39,600 --> 01:10:41,820
Robert Brandenberger, Prof.: yeah yeah i'm okay with this of it.

555
01:10:42,690 --> 01:10:42,990
Okay.

556
01:10:44,790 --> 01:10:54,480
Abhay Vasant Ashtekar: Since you're still not going, this is what he said that there is actually some ideas, more recently, about just doing quantum field theory in cosmological space times.

557
01:10:55,020 --> 01:11:05,790
Abhay Vasant Ashtekar: We seem to suggest that what one might have to use is really distributional geometries and perhaps then what you're calling continuous bounce can be absorbed into this.

558
01:11:06,570 --> 01:11:13,560
Abhay Vasant Ashtekar: Much more general paradigm of distribution geometries I just want you to just mentioned it to you and we can talk about later since you're like oh.

559
01:11:13,770 --> 01:11:14,520
Robert Brandenberger, Prof.: that's interesting.

560
01:11:15,840 --> 01:11:25,110
Robert Brandenberger, Prof.: So it's it in a certain sense of different way of going beyond the standard in my sense effective field theory description.

561
01:11:25,140 --> 01:11:26,130
Abhay Vasant Ashtekar: Yes, yes.

562
01:11:26,820 --> 01:11:28,830
Abhay Vasant Ashtekar: Because it was based on geometry is.

563
01:11:28,830 --> 01:11:33,810
Abhay Vasant Ashtekar: Becoming distribution, which is certain is the effective date is usually flexibility this.

564
01:11:34,950 --> 01:11:38,790
Robert Brandenberger, Prof.: What do you see there was a little bit of vacuum I talk, namely the S brain.

565
01:11:39,420 --> 01:11:42,450
Abhay Vasant Ashtekar: that's the district, yes, exactly that's why I was mentioned.

566
01:11:42,540 --> 01:11:48,180
Robert Brandenberger, Prof.: Exactly motivated it from the matches sexual, but you can you there's no special reason that it comes from the night.

567
01:11:48,900 --> 01:11:49,440
Jorge Pullin: Before you.

568
01:11:50,160 --> 01:11:50,400
Okay.

569
01:11:53,370 --> 01:11:59,850
Jorge Pullin: Okay, if there are no other questions, we should probably Robert go, he was kind enough to fill us with him to classes so let's thank the speaker again.

570
01:12:01,260 --> 01:12:05,430
Robert Brandenberger, Prof.: Thank you again for the invitation for all of the questions thank.

571
01:12:05,580 --> 01:12:06,510
psingh: You Thank you.