0 00:00:02,100 --> 00:00:11,530 Jorge Pullin: Okay. So today we have a panel on quantum black holes with machine hand prancing, and LED Wilson, it will be hosted by Vicar Hussein. So, Vicar, can you take it away? 1 00:00:11,890 --> 00:00:24,629 Viqar Husain: Yeah. So so thanks everyone for joining this. I'm hoping it'll be a very good discussion before I start. I just like to mention that it'd be useful if everyone waited for the 3 presentations to finish 2 00:00:24,800 --> 00:00:36,730 Viqar Husain: before asking questions that way. Everyone has enough time to finish, and then, and then we can proceed hopefully to a really good discussion. So you've all seen my first slide. I just have 2 slides. 3 00:00:36,870 --> 00:00:41,789 Viqar Husain: and I've put up here some questions that I have asked myself over the years. 4 00:00:42,080 --> 00:00:44,140 The first is. 5 00:00:44,340 --> 00:00:47,409 Viqar Husain: what does quantizing the Schwarzschild solution reveal? 6 00:00:47,690 --> 00:00:52,040 Viqar Husain: And I asked that question because the shorts of solution is just one solution. 7 00:00:52,170 --> 00:00:58,230 Viqar Husain: and we're looking at something much more complex in my view. So this is why I pose that question. 8 00:00:58,720 --> 00:01:02,889 Viqar Husain: The second question is, when we look at effective dynamics 9 00:01:03,360 --> 00:01:09,740 Viqar Husain: with perhaps just discreteness, corrections or other corrections, quantum corrections beyond just discreteness corrections. 10 00:01:10,220 --> 00:01:12,459 Viqar Husain: Then the question is. 11 00:01:12,930 --> 00:01:17,150 Viqar Husain: what does that reveal with matter and without matter, For example. 12 00:01:17,330 --> 00:01:22,459 Viqar Husain: does it provide evidence of Black Hole to Whitehold transitions, shockwaves? What else? 13 00:01:23,210 --> 00:01:28,380 Viqar Husain: And the reason I ask these questions is because, as we all know, the classical 14 00:01:30,270 --> 00:01:37,080 Viqar Husain: theory of scalar field collapse is extremely well understood, both from an analytical perspective and a numerical perspective. 15 00:01:37,530 --> 00:01:44,119 Viqar Husain: And one of the questions I've asked myself is, what's the quantum theory of this? So just very briefly. What we have here 16 00:01:44,190 --> 00:01:48,639 Viqar Husain: in the setting is that this is going. We're going back to the early nineties. 17 00:01:49,650 --> 00:02:00,319 Viqar Husain: we but there's weak data. This means that the scalar field. This is all in the asymptotically flat context and weak data means that the ATM mass is below a certain threshold. 18 00:02:00,340 --> 00:02:07,170 Viqar Husain: Then the scalar field just comes in and bounces back, goes back off, and there's no black hole, which is what I mean by just scattering 19 00:02:07,640 --> 00:02:18,880 Viqar Husain: and strong data is when the ATM. Mass is measured to whatever parameters in the scalar field profile that you put in is above a certain threshold, and then there's always Black Hole formation. 20 00:02:19,370 --> 00:02:27,529 Viqar Husain: and then there's a transition reason between the 2, which is an extremely finely tuned, naked singularity about which a lot has been written. 21 00:02:28,300 --> 00:02:31,829 Viqar Husain: So the basic question here is, what is the quantum theory. 22 00:02:31,900 --> 00:02:37,480 Viqar Husain: and the broader question is, is matter necessary for a complete understanding of quantum black holes. 23 00:02:38,570 --> 00:02:49,490 Viqar Husain: And so the recent work, the LED and I and our students have done is that effective theory of dust collapse may provide a hint to this bigger problem. 24 00:02:49,660 --> 00:02:54,510 Viqar Husain: which is that you have some form of collapse, some type of metastable black hole. 25 00:02:54,880 --> 00:03:03,119 Viqar Husain: and then some outward going burst, maybe a shock wave. And perhaps this process continues because this matter goes out. Gravity starts to pull it back in. 26 00:03:03,200 --> 00:03:09,320 Viqar Husain: and so is this going to continue forever this kind of oscillation of matter collapsing and then bouncing. 27 00:03:09,520 --> 00:03:14,779 Viqar Husain: So those are just 3 comments I wanted to make, and then let me just go to the next slide. 28 00:03:14,930 --> 00:03:18,519 Viqar Husain: which is what our 3 panelists are going to talk about. 29 00:03:18,890 --> 00:03:22,830 Viqar Husain: So first Perm will open with the Lqg. Of the Schwarzschild Solution 30 00:03:23,060 --> 00:03:27,169 Viqar Husain: Interior exterior comparison of approaches and open questions. 31 00:03:27,850 --> 00:03:32,209 Viqar Husain: and then machine will talk about covariant, effective dynamics 32 00:03:32,810 --> 00:03:39,759 Viqar Husain: for vacuum for spherically symmetric space times, and in particular, that a solution of those equations 33 00:03:39,780 --> 00:03:43,560 Viqar Husain: and some comments on the Black Hole by whole transition from this perspective. 34 00:03:43,950 --> 00:03:52,960 Viqar Husain: And then, thirdly, it will talk about the recent work on Ltd. The mitochondria toll on Bondi models and dust collapse. 35 00:03:53,400 --> 00:03:59,540 Viqar Husain: and how that gives this effective equations give rise to weak solutions which predict shock waves. 36 00:03:59,590 --> 00:04:06,679 Viqar Husain: and how this shows dynamical singularity, resolution, and it will also talk about implications for the Information 37 00:04:06,840 --> 00:04:08,010 Viqar Husain: lost problem. 38 00:04:08,460 --> 00:04:12,960 Viqar Husain: So that's those are my opening remarks. And so, Baham, please take it away. 39 00:04:15,160 --> 00:04:16,500 psingh: Okay. 40 00:04:16,600 --> 00:04:18,129 psingh: Thank you very much for your car. 41 00:04:20,529 --> 00:04:22,360 psingh: So i'm going to start with 42 00:04:23,730 --> 00:04:25,799 psingh: the loop. Can everyone see my screen. 43 00:04:27,520 --> 00:04:28,330 Abhay Vasant Ashtekar: Yes. 44 00:04:28,710 --> 00:04:30,780 psingh: okay. So i'm going to. 45 00:04:30,990 --> 00:04:34,280 psingh: I'm going to start this panel discussion essentially for making of 46 00:04:34,420 --> 00:04:36,630 psingh: platform, also for motion and 47 00:04:36,720 --> 00:04:44,520 psingh: at stock, which deal more with the dynamicals and stock, deal more with the dynamical scenario and motion Stock is essentially in the middle of 48 00:04:44,780 --> 00:04:47,490 psingh: where I would be pitching my token network 49 00:04:47,640 --> 00:04:49,060 psingh: be pitching his talk. 50 00:04:49,130 --> 00:04:55,750 psingh: So i'll be discussing the work which I have done with Abbe and Javier couple of years ago, and we have been 51 00:04:57,230 --> 00:05:01,920 psingh: following this trajectory, and various of the generalizations of this model have been studied. 52 00:05:02,410 --> 00:05:03,190 psingh: So 53 00:05:04,470 --> 00:05:05,410 psingh: let me 54 00:05:05,760 --> 00:05:07,730 psingh: go to a brief introduction. 55 00:05:08,660 --> 00:05:13,069 psingh: We are essentially trying to study the loop quantization of 56 00:05:13,360 --> 00:05:16,280 psingh: the Crusco basically the critical space time. 57 00:05:16,780 --> 00:05:17,550 psingh: And 58 00:05:17,920 --> 00:05:27,940 psingh: one thing which is very useful for understanding the Schwarzschild Black Hole, shorter and tea is that it is isometric to the Kentucky sex vacuum cosmology. 59 00:05:28,460 --> 00:05:34,779 psingh: And since it's a since one can choose a homogeneous slicing, as in the cosmological models. 60 00:05:35,410 --> 00:05:38,830 psingh: people started applying the loop on this allergy techniques 61 00:05:39,000 --> 00:05:41,289 psingh: to understand what happens 62 00:05:41,320 --> 00:05:46,879 psingh: to the singularities in this, especially the central singularity in this inside the Black Hole. 63 00:05:47,360 --> 00:05:50,190 psingh: Basically how does a quantum Romanian geometry 64 00:05:50,370 --> 00:05:55,529 psingh: changes the space time near the similarity. What are the blank scale effects? 65 00:05:55,600 --> 00:06:04,670 psingh: And the intuition was that very similar to what we will see in the we have the quantityometry effects lead to a universal bounds on space-time curvature 66 00:06:04,690 --> 00:06:06,900 psingh: kind of bounce a picture of big 67 00:06:06,980 --> 00:06:08,720 psingh: a similar picture about the merge 68 00:06:08,750 --> 00:06:17,569 psingh: in the loop cultivation of Schwarzschild black holes, and these attempts have been going on for very long time, starting from 2,005 and sticker and volume all, and then 69 00:06:17,970 --> 00:06:27,929 psingh: later on, like polymer and vendor, slow, then so on, and like many in this, especially up to like 2,018, 2,019. There has been a flood of various papers 70 00:06:28,110 --> 00:06:30,430 psingh: trying to understand different models in detail. 71 00:06:31,100 --> 00:06:38,600 psingh: The spatial metric is homogeneous, so that makes life easier to understand this interior, using the cosmology code 72 00:06:38,710 --> 00:06:44,139 psingh: analogies. But the metric is not isotropic. It is an isotropic. 73 00:06:44,330 --> 00:06:45,090 psingh: So 74 00:06:45,130 --> 00:06:54,380 psingh: the Kentowski sax. If you just look at the Kentowski sex cosmology the singularity is like a cigar like the When the 11 approaches the Big Bang. In personality 75 00:06:55,040 --> 00:07:07,580 psingh: the problem becomes technically challenging, because not only there is a while curvature, but also there is a spatial curvature, so an isotropy and spatial cur, which are both, are now clock together. They both play a very important role. 76 00:07:07,750 --> 00:07:10,049 psingh: and that is where the conversation has been 77 00:07:10,480 --> 00:07:11,330 psingh: more 78 00:07:11,430 --> 00:07:13,309 psingh: difficult to understand. 79 00:07:13,990 --> 00:07:17,190 psingh: So. But the physical implication has been studied by many groups. 80 00:07:17,230 --> 00:07:22,399 psingh: and I'm. I'm. I really apologize if I miss some of the names, but I've tried to pull 81 00:07:22,480 --> 00:07:24,280 psingh: as many names as possible. 82 00:07:24,560 --> 00:07:27,170 psingh: There are 2 important caveats in. 83 00:07:28,030 --> 00:07:36,239 psingh: When we try to understand this picture. The first caveat is that this is an idealized picture of an internal black hole. We are not looking at a dynamical collapse scenario. 84 00:07:36,390 --> 00:07:46,210 psingh: and there is no proof yet that any of the conversations which have been studied so far they arise from a dynamical collapse scenario. So that is a in my personal viewpoint. That's an 85 00:07:46,810 --> 00:07:49,760 psingh: open, unsolved problem which we still try. 86 00:07:49,810 --> 00:07:51,590 psingh: which we still have to understand. 87 00:07:51,610 --> 00:08:00,009 psingh: The second very important caveat is that almost all of the results which various people have obtained, including for the dynamic other situations which 88 00:08:00,140 --> 00:08:01,570 psingh: Mission and Edward 89 00:08:01,590 --> 00:08:04,810 psingh: talk about Later, one is assuming 90 00:08:05,060 --> 00:08:08,530 psingh: the validity of an effective space-time description. 91 00:08:08,800 --> 00:08:16,949 psingh: an effective continuum space time description in which one starts from classical Hamiltonian constraint and one polymerizes it and then one is trying to understand various effects 92 00:08:16,990 --> 00:08:19,649 psingh: coming from this effective space and description. 93 00:08:19,840 --> 00:08:35,559 psingh: We do not know how valid is this effective spacetime description for the Black Hole Space Times. But the good news is that, at least for the cosmological models when you have, while curvature, then very sophisticated simulations for wide variety of States 94 00:08:35,679 --> 00:08:36,400 psingh: for 95 00:08:36,500 --> 00:08:40,009 psingh: an isotropic model show that this effective space-time description is 96 00:08:40,059 --> 00:08:41,289 psingh: quite accurate. 97 00:08:41,720 --> 00:08:44,819 psingh: But still this this is 98 00:08:45,530 --> 00:08:52,449 psingh: okay. So with this: let me come to the classical aspects. And this is the only slide which you'll have most of the equations, because i'm setting the stage. 99 00:08:52,770 --> 00:09:00,850 psingh: The special manifold is our cross s 2, and this has a judicial metric which is given by this particular equation. 100 00:09:00,910 --> 00:09:04,389 psingh: and one notices that there is a non-compact 101 00:09:04,640 --> 00:09:06,330 psingh: X direction which 102 00:09:06,360 --> 00:09:15,490 psingh: for which coordinates for L. Naught, and you have to choose a traditional cell to define the simpleactic structure, and for the cylindrical traditional cell we it 103 00:09:15,570 --> 00:09:19,499 psingh: make it's volume as B. Not as 4 by R, not square. L. 104 00:09:19,750 --> 00:09:26,279 psingh: Then, using this underlying symmetries, the connection and the triads, they can be written in the form of these 2 equations. 105 00:09:26,490 --> 00:09:40,759 psingh: and one can choose a convenient set of variables such that the the of the the pose on brackets do not depend on are not an Ln. And the ideas, then you would choose C. And P. C. And B. And P. Be in this particular form 106 00:09:41,210 --> 00:09:58,060 psingh: the moment you do that one understands that they are also rescaling properties; that under L, not going to some rescaling alpha, I will not see changes in this particular way, and Pv. Changes in this particular way, C goes to our Pb. But DC. And B. They remain invariant. 107 00:09:58,520 --> 00:10:05,540 psingh: The the lesson from loop on on the smallogy and from areas of the post multiple models is that this pollution, then, should not play any role. 108 00:10:05,560 --> 00:10:06,330 and 109 00:10:06,410 --> 00:10:08,270 psingh: for physically relevant 110 00:10:08,940 --> 00:10:12,469 psingh: of zoom, but like the freshman scalar or the ske of the white. 111 00:10:12,790 --> 00:10:13,669 psingh: and so on. 112 00:10:13,760 --> 00:10:21,590 psingh: and the curvature scale at the B should not depend on this alpha, and this is one of the main requirements which we can pose for 113 00:10:21,610 --> 00:10:26,790 psingh: demanding a consistent conversation. And in this talk I'm. Going to talk mainly on 114 00:10:26,890 --> 00:10:33,850 psingh: the how we obtain this consistent conversation, and how we how this consistent conversation compares with other schemes. 115 00:10:34,320 --> 00:10:38,869 psingh: One thing to notice is that the classical horizon in this, in this 116 00:10:38,970 --> 00:10:40,110 psingh: space time 117 00:10:40,180 --> 00:10:48,039 psingh: corresponds to when Pb. Becomes equal to 0. PC. Becomes equal to 4 M. Square, and at the horizon B also becomes equal to 0. 118 00:10:48,700 --> 00:11:05,749 psingh: Similarity Central singularity occurs at Pb. Equal to 0 and PC. Equal to 0. So whatever scheme which we want to build from, but when we try to quantize the fury, we have to be very careful. How do we choose this Delta V and Delta, c. 119 00:11:05,890 --> 00:11:08,079 psingh: And I will come up with these questions down. 120 00:11:08,720 --> 00:11:09,430 psingh: So 121 00:11:10,310 --> 00:11:13,550 psingh: so let us look at if it if one looks at the 122 00:11:14,500 --> 00:11:21,889 psingh: if one looks at the quantum aspects, the the general idea of the quantum aspects, the procedure remains very similar to what we do in the loop quantization of 123 00:11:22,600 --> 00:11:28,509 psingh: homogeneous Space Times. One starts from a classical Hamiltonian constraint. One expresses those 124 00:11:28,640 --> 00:11:31,799 psingh: the quantities in terms of the 125 00:11:32,150 --> 00:11:43,099 psingh: connection and the flux of the triad. And then there are certain polymerizations which happen from a non local nature of the field strength, and then one is trying to understand the physics of that Hamiltonian constraint. 126 00:11:43,370 --> 00:11:53,489 psingh: But different conversations are available because this is a a much more complicated scheme than a single isotopic Ilw space time. There are lots of cultivation. Ambiguities 127 00:11:53,510 --> 00:11:54,989 psingh: which are also good 128 00:11:55,020 --> 00:12:00,820 psingh: and different accommodations, results from different ways of expressing this curvature in terms of. 129 00:12:00,860 --> 00:12:03,060 psingh: and how the smallest loop area 130 00:12:03,250 --> 00:12:09,090 psingh: assign using quantum geometry. And there have been different procedures to do that. People have looked at different 131 00:12:09,140 --> 00:12:10,250 psingh: based on that. 132 00:12:10,370 --> 00:12:15,800 psingh: But basically, the punchline is that the quantum constraint consists of terms like this, signed delta B 133 00:12:15,920 --> 00:12:26,609 psingh: by delta, B, and sign delta, c. By 10 to C with delta B is a fractional length of each link of the placket on the theta 5 to sphere and Delta, c. Is the fractional length 134 00:12:26,700 --> 00:12:32,429 psingh: of the links in the X direction for the plackets in the P to X. And 5 explains in this on this 135 00:12:32,980 --> 00:12:34,140 psingh: in this manifold. 136 00:12:34,460 --> 00:12:41,159 psingh: Now the departure from the classical theory should only offer in the plank regime, and not when the space time curvature is small. 137 00:12:41,270 --> 00:12:51,080 psingh: This is a requirement which we must put, because if you have a departure which is happening at very small space and curvature, the huge departure happening at very small space time, per which of all 138 00:12:51,330 --> 00:12:55,690 psingh: a large microscopic black horse, then we know this conversation is going to be ruled out. 139 00:12:55,750 --> 00:12:56,940 psingh: My observation. 140 00:12:57,170 --> 00:12:57,920 psingh: So 141 00:12:58,270 --> 00:13:02,670 psingh: the the point is like, as in the early days of loop on the small G, they were 142 00:13:02,710 --> 00:13:03,440 so. 143 00:13:03,660 --> 00:13:12,969 psingh: some oversight which were made. Similarly similar things happen in the Black Hole Space time, and slowly, as we are understood, we understand the physical implications on the phenomenology. We have been 144 00:13:13,160 --> 00:13:14,860 psingh: trying to come to the night model. 145 00:13:14,950 --> 00:13:31,800 psingh: So that is why I put them there many pitfalls, even though the models may seem non singular, so you may start from some delta V and delta, c. Of your liking, like simplest choice being let us put Delta V and Delta, c. As some constants numerical constants. And when you write down the quantum constraint, and that will look like a 146 00:13:32,060 --> 00:13:37,550 psingh: finite difference equation, Which will you? And you may think about. This equation is non-singular. 147 00:13:37,660 --> 00:13:40,759 psingh: That does not imply that you really have a 148 00:13:40,900 --> 00:13:45,309 psingh: physically consistent picture, because it can happen that you may have 149 00:13:45,390 --> 00:13:47,970 psingh: very large space 150 00:13:48,030 --> 00:13:52,709 psingh: coming from the these polymerization terms, even when you expect that 151 00:13:53,030 --> 00:13:54,809 psingh: you should not have, and you may. 152 00:13:54,910 --> 00:13:57,720 psingh: Your model may be just ruled out by observations. 153 00:13:57,890 --> 00:13:58,630 psingh: So 154 00:13:58,810 --> 00:14:03,930 psingh: we are some of the questions one can post. Is space-time curvature at singularity resolution universal 155 00:14:04,030 --> 00:14:04,870 psingh: or 156 00:14:04,970 --> 00:14:08,810 psingh: If it is not universal, how does it scale with the mass of the blackboard. 157 00:14:09,150 --> 00:14:12,280 psingh: Finally, we would like it to be universal. 158 00:14:12,420 --> 00:14:19,249 psingh: because we have seen a very similar thing happens in group on the smallest. We have the energy density at the bounce turns out to be universal. 159 00:14:19,790 --> 00:14:20,470 psingh: But 160 00:14:20,690 --> 00:14:29,189 psingh: if it's not universal, how does it scale that mass? Certainly we do not want to have a scenario or a model, where, if you take a very large mask, then the scale 161 00:14:29,710 --> 00:14:33,480 psingh: yeah, it goes inversely with mass or some other inverse power with mass. 162 00:14:34,450 --> 00:14:43,849 psingh: one very important property, and and this which which we need to understand in this model, and this model gives us a very unique opportunity to 163 00:14:43,990 --> 00:14:50,329 psingh: bring this out is to loop quantum effects, distinguish physical versus the coordinate similarity. 164 00:14:50,380 --> 00:14:58,529 psingh: So in this picture, which we have, we have a central singularity inside the blackboard, but at the horizon. And these coordinates there is also coordinate similarity. 165 00:14:58,650 --> 00:15:08,599 psingh: But we know that just a coordinate singularity it is. It is pretty easy to write down a wrong polymerization scheme which does not distinguish the central singularity 166 00:15:08,630 --> 00:15:10,810 psingh: and the partner similarity in the sense 167 00:15:10,830 --> 00:15:18,349 psingh: that it, the plank scale effects will be also seen at the central singularity, and they are quantum gravity effects also the boarding and singularity. 168 00:15:18,620 --> 00:15:19,380 psingh: so 169 00:15:19,740 --> 00:15:26,040 psingh: it's not built in, as if if you think slightly. It it is easy to realize a group of gravity 170 00:15:26,840 --> 00:15:46,310 psingh: is not built in to really distinguish these 2. You can. You can easily make a mistake here, because one is essentially looking at the whole of the connection which is proportional to the extensive curvature, the globe in the extensive coverage it does not translate to the blow in the crash on scalar always, and so on, so there can be an ambiguity there. So this is a very important point. 171 00:15:46,750 --> 00:15:56,759 psingh: and then the next question is that Well, even if you have a checkm for the first 2, how symmetric is the P. Or me is your bounce so asymmetric that you start from a black hole. 172 00:15:57,030 --> 00:15:58,730 psingh: and let us say which is solar mass. 173 00:15:59,010 --> 00:16:01,830 psingh: And then on the other side, if there is a bound, you can 174 00:16:02,430 --> 00:16:10,399 psingh: bring all the white out, which is extremely extremely massive. And how does that happen? So there are many pitfalls and requirements. One can 175 00:16:10,540 --> 00:16:17,810 psingh: what one can put for a consistent quantization. Some of them, you may say, like they are probably more demanding like. 176 00:16:17,950 --> 00:16:24,269 psingh: and some of them are really like necessary things like you. Should one should be able to distinguish physical versus coordinate effects 177 00:16:24,380 --> 00:16:25,950 psingh: and better. 178 00:16:26,080 --> 00:16:28,249 psingh: How do you have models which are rolled out by 179 00:16:28,360 --> 00:16:29,420 psingh: observations? 180 00:16:30,680 --> 00:16:31,890 psingh: Okay. So 181 00:16:32,340 --> 00:16:37,269 psingh: Now i'll briefly talk about a prescription which is based on the transition service, and this was the word 182 00:16:37,360 --> 00:16:38,619 psingh: which I didn't 183 00:16:38,650 --> 00:16:40,110 psingh: and Javier 184 00:16:40,500 --> 00:16:41,769 psingh: couple of years ago. 185 00:16:42,410 --> 00:16:48,040 psingh: The idea is that if you to choose Delta, B and Delta, C in this prescription as G. Rock observers. 186 00:16:48,100 --> 00:16:53,170 psingh: then all the face based functions which are constants along dynamical trajectories. Then 187 00:16:53,190 --> 00:16:58,609 psingh: each you can show analytically that each solution is identified by a transition surface. 188 00:16:58,670 --> 00:17:02,249 psingh: This charity which occurs at this particular 189 00:17:02,300 --> 00:17:06,939 psingh: time, and then it joins a Black Hole region with the white whole region. 190 00:17:07,720 --> 00:17:15,470 psingh: This can be shown analytically, assuming the validity of effective dynamics. In all regimes this can be shown. You do not need nomadics to show this. 191 00:17:15,609 --> 00:17:20,119 psingh: So the idea which we proposed was that we consider plackets on the transition surface 192 00:17:20,140 --> 00:17:26,429 psingh: when the curvature invariance. Take the largest value, because we know that curvature invariance take largest value at the transition surface. 193 00:17:26,460 --> 00:17:27,579 psingh: and then we. 194 00:17:27,790 --> 00:17:34,689 psingh: using that transition surface as a guide and the plackets on the transition surface as the right, we determine what should be Delta, B 195 00:17:34,730 --> 00:17:35,950 psingh: and Delta, C, 196 00:17:36,180 --> 00:17:45,619 psingh: basically the physical fractional area for the analysts around equators computed at this transition surface determines the relation between Delta, C. Delta, V and Pb. As 197 00:17:46,460 --> 00:17:50,529 psingh: if this capital dies down, which is the minimum area coming from quantum geometry 198 00:17:50,570 --> 00:17:56,770 psingh: and the physical fractional area of 2 sphere of the transition service gives you another relation, and then 199 00:17:57,290 --> 00:18:00,060 psingh: for very large blackpools. This gives you 200 00:18:00,400 --> 00:18:04,860 psingh: the relation of Delta, B and M. And Delta, C. And I'm. In this way. 201 00:18:06,530 --> 00:18:16,680 psingh: then, we can compute the physics of the resulting model with the previous approaches, and here I am plotting one of the one of the relevant on observables. Pb. Versus 202 00:18:16,870 --> 00:18:18,790 psingh: the Time Capital, T. 203 00:18:19,030 --> 00:18:22,749 psingh: And I'm. Plotting various models here. So I have 204 00:18:23,570 --> 00:18:24,210 psingh: done. 205 00:18:24,300 --> 00:18:40,639 psingh: Dashed go this dotted curve, which is the Gr, which is this very faint line going like this from here and at this capital t equal to 0. There is this classical horizon. So it starts from here, and then this line goes in this direction, and the classical singularity will be read somewhere. 206 00:18:40,800 --> 00:18:41,430 Yeah. 207 00:18:41,920 --> 00:18:43,240 psingh: then, there is a 208 00:18:43,750 --> 00:18:52,709 psingh: Aos model which is the model I'm talking about in this. This is given by this dashed line like this: One starts from the classical 209 00:18:52,820 --> 00:18:53,780 psingh: horizon. 210 00:18:53,800 --> 00:18:56,830 psingh: and then there is a bounce, and then one reaches 211 00:18:57,000 --> 00:19:00,430 psingh: White hole like region on the other side. 212 00:19:00,690 --> 00:19:06,489 psingh: Then i'm up, comparing them with 2 other approaches, which one of the approaches is called this, which I gave it 213 00:19:06,570 --> 00:19:14,090 psingh: Alex. A few years ago. The Cs approach Cs approach has some similarities. With this as of Aos approach. 214 00:19:14,170 --> 00:19:21,379 psingh: And what happens is that this is given by this dash dotted line, but much later on, much much later on it will bounce, and then it will go into 215 00:19:21,420 --> 00:19:23,209 psingh: a much larger 216 00:19:23,530 --> 00:19:27,009 psingh: anti-track region, or a much larger white whole region. 217 00:19:27,770 --> 00:19:31,560 psingh: The difference between the Cs approach and Aos approaches essentially 218 00:19:31,680 --> 00:19:33,290 psingh: that the Cs approach 219 00:19:33,550 --> 00:19:38,089 psingh: has a very symmetric bounds, and then the richer scalar is such that 220 00:19:38,310 --> 00:19:45,450 psingh: at for very large macroscopic black holes, this the way to scale it becomes extremely small. That is not the case with the Us. Approach. 221 00:19:45,500 --> 00:19:53,860 psingh: and the other approach is this Bv approach, which is the Boimer vendors loop model, which was inspired by the improved dynamics in Loop, one of the smallaging. 222 00:19:54,080 --> 00:19:55,410 psingh: But this model has 223 00:19:55,600 --> 00:20:04,270 psingh: various problems, including near the horizon, and later on, so you can see, like even near the horizon, like there is. It's really disappointed 224 00:20:04,590 --> 00:20:12,510 psingh: to the horizon. But if you are away from this classical horizon. Then what happens is that after the bounds it goes into a 225 00:20:12,560 --> 00:20:14,530 psingh: series of 226 00:20:14,660 --> 00:20:21,329 psingh: bounces, and it doesn't really go into an anti-track region. But this space time for response to a 227 00:20:21,770 --> 00:20:23,209 psingh: constant curvature. 228 00:20:23,600 --> 00:20:29,169 psingh: a product of concept which are spaces which is essentially like, which can be written as an effective charge in AI 229 00:20:29,300 --> 00:20:32,040 psingh: space time. The problem is that as you 230 00:20:32,140 --> 00:20:46,500 psingh: and after the pounds one cannot really trust this effective description much because one reaches the scales of PC. Which are much smaller than in on the Area gap, and then the fluctuations will become large, and we do not know how well it is this effective picture. 231 00:20:46,830 --> 00:20:48,690 Viqar Husain: my firm. You have a couple of minutes. 232 00:20:48,780 --> 00:20:55,889 psingh: Okay, so I will just come to the curvature Invariance, and then the Aos picture would turn. One can show that the curvature invariance 233 00:20:55,990 --> 00:21:11,650 psingh: for this leading order term is a is is composed of a fundamental constants. We have this capital that I is essentially like gamma and healthy, and the connection terms go as M. Square, and you can see that the freshman scalar versus T. Takes this universal value here. 234 00:21:12,170 --> 00:21:25,509 psingh: and one can also extend this picture outside to the exterior. Now, in the exterior there is no homogeneous, homogeneous, spatial, slicing, but one can take time like hyper surfaces. And one can take this 3 metric with minus plus signatures. 235 00:21:25,580 --> 00:21:36,680 psingh: The cost is that one has to work with now connections and clients which are su 1 one value, and following the same strategy 1 one uses in the interior for Delta, V and Delta, c. One can 236 00:21:36,770 --> 00:21:48,320 psingh: One can also explode the exterior of which various detailed asymptotic properties have been studied. There is a as in product limit, but there are some we quantum corrections which are attained, and the fall of 237 00:21:48,550 --> 00:21:49,489 psingh: What was that? 238 00:21:49,700 --> 00:21:50,970 psingh: One or 4 239 00:21:51,510 --> 00:22:05,289 psingh: so essentially like? The picture in the middle is like a If you look at this middle diamond here, there is this black Hole space time. This green dotted line is the transition surface. The the past of this black hole is to send the the trap 240 00:22:05,390 --> 00:22:06,500 psingh: correct by 241 00:22:06,610 --> 00:22:13,199 psingh: the the past of the Stammon is a trap Service the future of this time, and it's the end. Trap surface, and it keeps on repeating. 242 00:22:13,220 --> 00:22:19,120 psingh: And this is a this is for very large microscopic black holes, and that is why we get a very symmetric picture 243 00:22:19,140 --> 00:22:19,890 psingh: cool. 244 00:22:20,130 --> 00:22:21,829 psingh: So let me just summarize 245 00:22:22,010 --> 00:22:29,890 psingh: the basically the lessons we have in from the loop foundation of the Schwarzschild Space Time are many, and 246 00:22:30,020 --> 00:22:37,750 psingh: unfortunately, like it is very difficult to summarize. In 10 min, 1015 min all the developments. So i'm just focused on the few main points. 247 00:22:37,990 --> 00:22:48,669 psingh: The main point is that the loop foundation of social space time is a pretty problem, because it's a while plus spatial curvature coming together, and we do not have that kind of 248 00:22:48,920 --> 00:22:52,289 psingh: quantization. Yet even in the loop one of the smaller. 249 00:22:52,590 --> 00:22:55,649 psingh: There there is the Yankee 9 is not fully done there. 250 00:22:55,720 --> 00:23:04,820 psingh: so ideas which have been quite successful in Lqc. They have to be used with caution. One cannot just arbitrarily assume that improved dynamics will work in this case 251 00:23:04,890 --> 00:23:13,409 psingh: it that fails very badly when one sees that, and that is, I think that is because we have really not understood how to apply it 252 00:23:13,460 --> 00:23:14,380 psingh: properly. 253 00:23:14,400 --> 00:23:27,699 psingh: The Aos prescription, guided by effective dynamics, provides a consistent picture of the physics. It passes various tests for viability based on that. Many other models have been Refinements have been developed which have been studied by various people. 254 00:23:27,930 --> 00:23:31,820 psingh: There is an there exists an infinite number of trapped and entrepreneurs. 255 00:23:31,940 --> 00:23:42,680 psingh: and these are consecutive as in protect regions, having the identical atmosphere. And this is in contrast with the polymer vendor. When it's loop stream, in which there is no such possibility. But one gets a charge in a. 256 00:23:42,770 --> 00:23:56,490 psingh: The television scale has an upper bound at the transition surface. And this is this terms out of, independent of the mass of the black hole for microscopic black horse, and the Gr. Is covered in no provision agents, I think, for me personally, the most important lesson 257 00:23:57,000 --> 00:24:06,860 psingh: doing even one people miss about. We are just looking at a tunnel black Hole, and it's a simpler situation. It's really not like it's it. It merges many complicated things together. 258 00:24:06,970 --> 00:24:19,450 psingh: and one has really gained lot of lessons for which cultivation, prescription will work, which moderation, prescription will not work, and that is, by demanding this physical and phenomenological consistency which has guided 259 00:24:19,500 --> 00:24:20,660 psingh: is foundation. 260 00:24:20,710 --> 00:24:25,040 psingh: The open question remains: what happens in the dynamical collapse scenarios. 261 00:24:25,060 --> 00:24:25,770 psingh: and 262 00:24:25,790 --> 00:24:28,749 psingh: what and whether we recover such a scheme 263 00:24:29,270 --> 00:24:30,310 psingh: after 264 00:24:30,340 --> 00:24:31,870 psingh: a black hole has for 265 00:24:32,080 --> 00:24:33,969 psingh: I will stop here. Thank you. 266 00:24:51,380 --> 00:24:52,700 Muxin Han: Should I start? 267 00:24:52,940 --> 00:24:53,860 Viqar Husain: Yes, please. 268 00:24:54,230 --> 00:24:55,060 Muxin Han: Okay. 269 00:25:09,570 --> 00:25:10,910 Muxin Han: Screen. 270 00:25:12,500 --> 00:25:15,260 Muxin Han: Yeah, we can see it. Okay, Thank you. 271 00:25:15,550 --> 00:25:17,849 Muxin Han: Okay. So so 272 00:25:18,220 --> 00:25:21,290 Muxin Han: So here this is my 273 00:25:21,460 --> 00:25:32,680 Muxin Han: discussion on effective dynamics. So in this, in this short talk i'm going to talk about basically 2 stories closely related. Firstly. 274 00:25:32,690 --> 00:25:49,779 Muxin Han: I will talk about covariant new bars scheme, effective dynamics of the spherical symmetric loop on gravity. This is a new result, and also the second story is I'm. Going to talk about a a even newer result on the full effective space time of the Black Hole Whitehole transition. 275 00:25:50,690 --> 00:25:58,889 Muxin Han: So, firstly, about effective dynamics. So i'm. Most of this talk will focus on effective dynamics. 276 00:25:59,180 --> 00:26:07,680 Muxin Han: So just for an overview. So they are. They are 2 categories of affecting models in you the pong ready black holes. 277 00:26:07,700 --> 00:26:26,340 Muxin Han: So far, so the the first categories are models based on the Kantowski Saxon variation, and these models has only finitely my number of degree of freedom because of the large symmetry like a Peram just to topped because the Kantowski saxophone there is a a homogeneous symmetry 278 00:26:26,370 --> 00:26:44,399 Muxin Han: then, and the slides is homogeneous, so there's a large symmetry in the end. After seemingly reduction. These models are only have finite number of a degree of freedom, and well in particular, the the model talks just talked about Peram, this Aos model. This belongs to this category. 279 00:26:45,270 --> 00:27:05,009 Muxin Han: and and there is another category, the second category. Can these models that reduce 40 gravity only by spherical symmetry? You know, result, using the homogeneous license, and those models are generally generally 1 one, plus one dimensional field series, and they are. They have 5 infinite many degree of freedom. 280 00:27:05,680 --> 00:27:09,639 Muxin Han: and these models are are including those references. 281 00:27:09,660 --> 00:27:17,450 Muxin Han: And and these field theory models has less symmetry, because so symmetry, reduction only respect to spiritual symmetry. 282 00:27:17,570 --> 00:27:29,100 Muxin Han: but because they are Field Series. So they are. They have richer in principle. They should have richer dynamical properties. And so here we are going to focus on the the model in the second category. 283 00:27:30,090 --> 00:27:45,129 Muxin Han: and the the new results is that we have a new scheme of effective dynamics, what we call a covariant new bar scheme, and this is the effective Hamiltonian that we propose very, very recently last year. 284 00:27:45,590 --> 00:28:04,770 Muxin Han: And so here some explanation for these for this Hamiltonian. So so, firstly, it depend on the canonical Variables, Exefi, and the accounting and moment I. T. X. And K. 5, and they are the the standard phase based variables for spherical symmetric con gravity. 285 00:28:04,870 --> 00:28:14,739 Muxin Han: And here this ex, if I are a relay relay relay relating to the spherical symmetry metrics. So this is a general spherical, specific, metric. 286 00:28:15,890 --> 00:28:32,899 Muxin Han: and here the congregate. Momenta and k-fi appear in this Hamiltonian by so-called a new of our hormones. So these are standard numer type for all of these that we use all the time for for for black holes, for spherical symmetric l, 2, G. 287 00:28:33,550 --> 00:28:52,310 Muxin Han: A. And so you can see that this Hamiltonian depend on the X and the K-fi. Only through those new bar follow me. And also you can check that this Hamiltonian go back to the ATM Hamiltonian when this delta goes to 0, and we start out. We should understand as a as the the minimal area gap in lupon gravity. 288 00:28:53,050 --> 00:29:03,070 Muxin Han: And this Hamiltonian. Importantly, this Hamiltonian is not a Hamiltonian constraint, but it is a true Hamiltonian. So so this Hamiltonian in principle 289 00:29:03,110 --> 00:29:13,350 Muxin Han: it it should be defined on certain, reveals space space. And this Ex. If I. T. S. K-fi are canonical audience of the reduced space base, this Hamiltonian is really a 200 and not a constraint. 290 00:29:13,610 --> 00:29:23,520 Muxin Han: and the effective having the effective dynamics is given by the Hamiltonian equation. With respect to this covariance you are effective dynamics, effective Hamiltonian. 291 00:29:23,570 --> 00:29:35,350 Muxin Han: and these equations are partial, differential equations on one plus one dimensions. And so the this is a a effective theory in in 2, dimensional, in in 2 dimensions 292 00:29:36,640 --> 00:29:43,199 Muxin Han: and in another important property is that this effective dynamics is generally covariant. 293 00:29:43,210 --> 00:29:57,040 Muxin Han: Yeah. And although it's, it's formulated in in the Hamiltonian formulation. But there is a a covariance behind this Hamiltonian, and you can derive this. Come to me by using Covariance. In that I will show in the next slide. 294 00:29:57,430 --> 00:30:14,219 Muxin Han: And this is important because there has been a a long debate on the covariance of effective dynamics in upon gravity, because usually the the effective dynamics are formulated. Using Hamiltonian formulation. It is not so manifest that those formulations are are covariant. 295 00:30:14,230 --> 00:30:29,899 Muxin Han: and these are some researchers for this long debate. But here I think we are able to show that and for these effective dynamics. This is really covariant, because well, there is a there is a lagrangian and manifestly covariant in the ground team behind it. 296 00:30:30,500 --> 00:30:32,790 Muxin Han: So so this is 297 00:30:33,030 --> 00:30:41,430 Muxin Han: this is the the log around them, behind the effective Hamiltonian. This is so-called mimatic gravity lagrangian. 298 00:30:41,460 --> 00:30:49,610 Muxin Han: and it has certain higher derivative interactions. And this is the general expression of these of the Lagrangian. 299 00:30:49,980 --> 00:30:55,109 Muxin Han: and it has the field Contents are, firstly, the metric gravity. 300 00:30:55,300 --> 00:31:10,520 Muxin Han: and they a additional scalar field, what they call me thating scalar, and there is also a log on the multiplier, and this loginary multiplier imposing it's, used to impose certain domestic constraints, something some constraint on theatic constraint. 301 00:31:11,000 --> 00:31:16,649 Muxin Han: And what is interesting is is that there is a a potential 302 00:31:17,100 --> 00:31:36,920 Muxin Han: containing all the higher derivative interactions. Now it's, it's it's function of Taiwan type 2. So this chi one is a box of I and T. 2 is finding new new, and this by menu, is second derivative. Of a scalar field 5. So so for this kind tool it already contained 4 4 derivatives. 303 00:31:37,160 --> 00:31:41,670 Muxin Han: right? And so these these ofi are some functions 304 00:31:41,710 --> 00:31:48,299 Muxin Han: of taiwan and Kai tool. So it's keep lots of higher derivative interactions. 305 00:31:49,210 --> 00:32:01,729 Muxin Han: and because you can see that when a Phi goes to 0, if go back to the known case, that gravity coupled to 9 notation dust, and this is the standard set up for the parameters for everything. 306 00:32:02,010 --> 00:32:19,830 Muxin Han: And in this, when we, a couple of gravity to 9 to 9 rotational dust, and you can use this scalar field to to perform as a clock field. And that is also what we are going to do is that this scalar field file is a clock field that defines the internal time 307 00:32:20,110 --> 00:32:27,500 Muxin Han: of the system. Yeah. And then, with respect to this internal time, you can de parameterize gravity and formulate the the physical Hamiltonian. 308 00:32:28,160 --> 00:32:31,590 Muxin Han: And this is exactly what we did. 309 00:32:32,420 --> 00:32:44,609 Muxin Han: that by by using the formation with this internal time, by using the constant 5 variation, and we can perform the Hamiltonian analysis with back to this valuation 310 00:32:44,630 --> 00:32:54,189 Muxin Han: and the Hamiltonian analysis of this Lagrangian with spherical symmetry, give it to precisely the Covariance, the new wire scheme Hamiltonian that I showed in the in the last slide. 311 00:32:54,550 --> 00:32:55,110 Yeah. 312 00:32:55,470 --> 00:33:11,609 Muxin Han: And then this Hamiltonian equation of the covariant Hamiltonian Covariance and Hamiltonian is equivalent to the mumatic gravity equation of motion. If you perform vibrational principle of this action, you will just get the same official motion as the effective dynamics. 313 00:33:12,730 --> 00:33:20,789 Muxin Han: and then the the this vacuum Hamiltonian is coming from the Hamiltonian and analysis with respect to the constant fire slice. 314 00:33:20,830 --> 00:33:23,260 Muxin Han: and it's generates the time, translation. 315 00:33:23,370 --> 00:33:26,109 respect to the internal time 5. 316 00:33:26,440 --> 00:33:42,130 Muxin Han: And what is interesting, here is a dual role played by this by this scalar field file. So, on one hand, it is serving as a clock field and help us to department trials on this system; and, secondly, the the higher derivative 317 00:33:42,140 --> 00:33:46,590 Muxin Han: interaction mediated by this scale of 5, 318 00:33:46,630 --> 00:34:02,419 Muxin Han: and precisely results in the new boss scheme polymerization, and it keeps the whole me corrections in the Mubarak scheme. So what we call holomi corrections in the Hamiltonian formulation are actually the the higher the derivative of interactions in the in the. 319 00:34:03,730 --> 00:34:15,690 Muxin Han: And so here, by relating this Hamiltonian to the covariant Lagrangian. We see that this new bars in the effective dynamics of spherical symmetry look on. Gravity is in this generally covariant 320 00:34:15,780 --> 00:34:18,600 Muxin Han: because it is manifest at the level of. 321 00:34:19,100 --> 00:34:25,860 Muxin Han: and it also suggests that the micro mmetic gravity Lagrangian is the effective lagrangian of loop on gravity. 322 00:34:25,960 --> 00:34:28,550 Muxin Han: at least in the spherical symmetric setup. 323 00:34:28,929 --> 00:34:47,959 Muxin Han: Okay, and, by the way, this this kind of idea is not completely new. It is already a point out by some early literature, by by Macron and collaborators, and also Karim and his collaborators. So here we are able to realize it in in the in the spherical symmetric 324 00:34:48,170 --> 00:34:49,209 black hole. 325 00:34:49,429 --> 00:34:51,459 Muxin Han: spherical symmetric on. Grab it 326 00:34:52,190 --> 00:35:09,070 Muxin Han: All right. So let's look at the effective dynamics, for by looking at some special solutions. So here we can solve those effective equations and with yeah, with some semi-free assumption. 327 00:35:09,080 --> 00:35:21,330 Muxin Han: and to get some analog of the Schwarzschild Black hole. So here we are going to assume a global killing field. And this killing field is time like and outside the keeping Verizon. 328 00:35:21,900 --> 00:35:27,499 Muxin Han: Yeah. And secondly, we are going to impose asymptotic Schwarzschild boundary condition far away from the Black Hole. 329 00:35:28,120 --> 00:35:47,040 Muxin Han: So with these 2 assumptions we are able to uniquely determine the solution. And this is the spacetime effective spacetime given by this solution. So you can see that this is, the solution is very different from the the Aos mode also. But this is, I think, this is a feature from the new bar 330 00:35:47,050 --> 00:35:48,429 regularization. 331 00:35:48,770 --> 00:35:50,430 Muxin Han: You are polymerization. 332 00:35:50,900 --> 00:35:59,430 Muxin Han: and and here, so, so there are 3 important features. So, firstly, the spacetime is singularity free. 333 00:35:59,450 --> 00:36:16,899 Muxin Han: and and there is a complete future infinity, and by the future infinity of the Black Hole approach asymptotically to the narrative. Elementary Ds. 2 across as 2. And this is the picture. This kind of picture is very similar to the the earlier model by by polymer and bundle's, not one that smooth 334 00:36:17,380 --> 00:36:35,389 Muxin Han: also here that we are free of all the problem of that model, so, as far as I mentioned, there was model that it it give large quantum correction at the horizon, and also it keeps the the the area of the se or smaller than the area gap. And those problems are are not here. 335 00:36:35,400 --> 00:36:39,209 Muxin Han: Yeah, it's an 336 00:36:39,560 --> 00:36:48,130 Muxin Han: okay. And so these space-time is really complete. And and furthermore, this spacetime has companies where, plus 337 00:36:48,390 --> 00:37:02,270 Muxin Han: yeah, and it contain 2 cars, and there is a standard scribe plus corresponding to the affinity of the commercial space time, and there is also a space like right plus, and and which is the square plus of of the the digital space. 338 00:37:03,500 --> 00:37:12,959 Muxin Han: And because of because there's no event, Verizon, but they are kidding providers, and and those are the Keying horizons are still there. 339 00:37:13,480 --> 00:37:22,700 Muxin Han: and here the holiday corrections is negligible as a cleaning price it means that at the low curvature regime and this this solution are are semi-casco. 340 00:37:23,840 --> 00:37:36,549 Muxin Han: Okay, so these are the some one simple solution coming from the effective equation. But, as I said, and this effective equation is a one plus one dimensional field theory, it in principle it contains much more than one. 341 00:37:36,560 --> 00:37:53,099 Muxin Han: These much more dynamical solutions. And then this is something actually open and to be understood is is how to go beyond the killing symmetry. And I understand the dynamical equation, understand the researcher dynamical poverty. 342 00:37:53,110 --> 00:38:05,980 Muxin Han: and and to get the the dynamical effect in spacetime, you will see in the next slide that indeed, we need a dynamical space time to to understand, for example. 343 00:38:06,160 --> 00:38:22,019 Muxin Han: And this is the the the second story that i'm going to talk about is, it is a new result, and that I I obtain with with cargo really, and and and and his student flash it. 344 00:38:22,970 --> 00:38:30,850 Muxin Han: And and this model is also a closely relates to to some earlier work by by Youriculumodowski in Gamma, Yang, and John. 345 00:38:31,890 --> 00:38:36,870 Muxin Han: and and here we or 10 a a really a full picture 346 00:38:36,920 --> 00:38:42,250 Muxin Han: of black holes. Why call transition without using the effective equation? Yeah. 347 00:38:42,390 --> 00:38:45,280 Muxin Han: Last, largely, we saw using that equation. 348 00:38:45,510 --> 00:38:56,229 Muxin Han: And then this, this spacetime. So this is the parallel diagram of of the of the entire space time, of entire geometry, of of blackboard Wifi foundation. 349 00:38:56,940 --> 00:39:05,690 Muxin Han: And so here it contains everything. The the spacetime includes the the gravitational collapse of the star. So there is a gravitational collapse of the star. 350 00:39:05,840 --> 00:39:15,750 Muxin Han: and there is a black hole horizon. So this is a black hole horizon. This is a black hole. Horizon is transit between white for Black Hole, and it has a single asymptotic region. 351 00:39:15,810 --> 00:39:18,249 Muxin Han: Okay, it has a single asymptotic region. 352 00:39:18,850 --> 00:39:22,179 Muxin Han: Yeah, and also it has to be region. 353 00:39:22,230 --> 00:39:35,419 Muxin Han: This is dynamical region, joining between Black Hole, transiting between black over and whiteful transition, and it used to be sync that this. This B region is a mystery that is highly dynamical. 354 00:39:35,820 --> 00:39:45,640 Muxin Han: And but right now we show that there is a metric. There is an effective matrix. We all define regular in in this in this region. 355 00:39:45,790 --> 00:39:54,140 Muxin Han: Okay. So so in the end we get a full effective, that effective, metric, effective geometry of the entire Black hole for transition space time. 356 00:39:54,850 --> 00:40:11,210 Muxin Han: Yeah. So here the construction of geometry involves the junction condition with the star, the killing symmetry, and the interpolation of geometry in the B region, but the effective equation is not used. Also it's it's it's used the inside star, but not outside the stuff. 357 00:40:11,660 --> 00:40:17,280 Muxin Han: So here it contained some key properties that, firstly, the gravitational collapse. 358 00:40:17,450 --> 00:40:25,809 Muxin Han: It is homogeneous, and pressure is a, and it is governed by Lqc. Effective equation, and it gives a symmetric bounce 359 00:40:26,220 --> 00:40:34,360 Muxin Han: and outside Star, and there is a regular infected metric cover, the entire vacuum space-time, and gives the black hole white Hope foundation. 360 00:40:34,990 --> 00:40:40,360 Muxin Han: and in particular there is a regular metric in the region B, which was a mystery before. 361 00:40:40,750 --> 00:40:49,550 Muxin Han: and and this this region B has a, and has the black hole like Horizon trans it to to Whitehole. Right? 362 00:40:49,570 --> 00:40:53,680 Muxin Han: That's why this is highly dynamical. It's a highly dynamical metric inside the 363 00:40:53,970 --> 00:40:56,540 Muxin Han: and outside the star there is a killing symmetry. 364 00:40:56,640 --> 00:41:07,990 Muxin Han: We're, and there is a killing symmetry everywhere except in the region B, and the key in symmetry is broken in the dynamical region. B. But you know, As I said, there is a regular metric inside. 365 00:41:09,280 --> 00:41:18,569 Muxin Han: All right. Let's come to the conclusion and and questions. So here I I showed 2 stories. On one hand we have a effective dynamics. 366 00:41:18,610 --> 00:41:31,629 Muxin Han: which is nice, generally covariant. And this is dynamical, and it's one dimensional it's one plus one-dimensional field theory containing the reach dynamic in principle, contains reach dynamical information. 367 00:41:32,310 --> 00:41:47,490 Muxin Han: On the other hand, we have a full spacetime of blackboard whitehole transition, and although these full spacetime geometry doesn't really use the the fact that the at the at the backing part of this full space time doesn't really use the fact, the equation. 368 00:41:48,000 --> 00:41:53,319 Muxin Han: Yeah. And this is constructed by using symmetry, considerations, and some interpolation technique. 369 00:41:53,920 --> 00:42:02,409 Muxin Han: And then about this this: this is really a full space time containing the B region and this B region it is dynamical relates to quantum effect. 370 00:42:02,490 --> 00:42:05,500 Muxin Han: but it has a regular effective metric in time inside. 371 00:42:05,720 --> 00:42:11,399 Muxin Han: and so it suggests that there should be some effectively dynamics. The effective description 372 00:42:11,460 --> 00:42:13,159 Muxin Han: we'll see in this region. B: 373 00:42:13,230 --> 00:42:18,729 Muxin Han: We're the dynamic. Yeah. So the dynamical, the effective dynamics should be valid inside. 374 00:42:19,690 --> 00:42:38,339 Muxin Han: Then the question is how to relate this to perspective, namely, how to really derive the full picture of black holes. Whitehole transition from the attractive dynamics really gives the effective dynamics. It keeps the effective block around them, where, in fact, the Hamiltonian write down the equation really derived from top to down 375 00:42:38,350 --> 00:42:42,790 Muxin Han: these black hole whiteboard transition, the full spacetime of black-hole transition. 376 00:42:43,250 --> 00:42:48,710 Muxin Han: This is the first interesting, interesting question in my mind, and, secondly. 377 00:42:48,910 --> 00:42:56,879 Muxin Han: even more interesting is that how to implement the hawking radiation and back reaction to the Black Hole, Whitehole transition and effective dynamics. 378 00:42:57,200 --> 00:42:59,950 Muxin Han: Yeah, I think that's all I want to say. Thank you. 379 00:43:02,560 --> 00:43:03,639 Viqar Husain: Okay, thanks. 380 00:43:03,850 --> 00:43:05,019 Viqar Husain: You want to start, please. 381 00:43:05,310 --> 00:43:05,930 Viqar Husain: Thanks. 382 00:43:15,980 --> 00:43:17,599 Edward Wilson-Ewing: All right. Do you see my screen? 383 00:43:19,680 --> 00:43:20,540 Abhay Vasant Ashtekar: Yes. 384 00:43:20,650 --> 00:43:36,370 Edward Wilson-Ewing: alright, okay. So I scored, too, so i'll try and be a little bit fast, so we can have a little bit more time for discussion. So, for my part of the panel, I want to present some work that did with the car, Jared, and 385 00:43:36,670 --> 00:43:40,559 Edward Wilson-Ewing: which concerns Black Hole collapse in L on gravity. 386 00:43:40,920 --> 00:43:44,570 Edward Wilson-Ewing: So this will very much build on what prom and we should have talked about 387 00:43:44,600 --> 00:43:49,050 Edward Wilson-Ewing: so hopefully. All 3 parts will fit together nicely. 388 00:43:50,520 --> 00:44:02,019 Edward Wilson-Ewing: Let me just mention that there are 2 outstanding problems for for black holes. One is the singular problem. One is the information loss problem, I think, in loop quantum gravity. We have 389 00:44:02,290 --> 00:44:11,570 Edward Wilson-Ewing: a reasonably good understanding of how the singularity is resolved. It's replaced by non singular bounce. Some of the details still remain to be ironed out, but I think 390 00:44:11,940 --> 00:44:16,270 Edward Wilson-Ewing: at a qualitative level. We understand this reasonably well. 391 00:44:16,300 --> 00:44:22,029 Edward Wilson-Ewing: but we know a little bit less about the information loss problem. So I also want to talk a little bit about this. Towards the end of my talk 392 00:44:23,980 --> 00:44:33,529 Edward Wilson-Ewing: in the work that we did, our goal was to understand how quantum gravity effects show up in black whole models starting from the initial collapse. And 393 00:44:33,710 --> 00:44:35,510 Edward Wilson-Ewing: there were 2 reasons that we 394 00:44:35,560 --> 00:44:43,129 Edward Wilson-Ewing: we wanted to really focus on collapse models. So the first one was that we were interested to see how the singularity is avoided dynamically. 395 00:44:43,150 --> 00:44:44,060 Edward Wilson-Ewing: So 396 00:44:44,240 --> 00:44:50,490 Edward Wilson-Ewing: if you really start with a space time where you have some distribution of matter which is completely non-singular. Then. 397 00:44:50,910 --> 00:44:59,300 Edward Wilson-Ewing: if this distribution collapses forms the black hole, then presumably the singular will be avoided dynamically. We wanted to get a good understanding of how that may happen. 398 00:45:00,330 --> 00:45:05,530 Edward Wilson-Ewing: The other thing that we were interested in was the role of matter. So if you have a 399 00:45:05,640 --> 00:45:16,819 Edward Wilson-Ewing: a black hole in classical gr, you have a singularity, so your matter will eventually hit the singularity and essentially disappear. But if you don't have a singularity, could stick around, it could play an important role. 400 00:45:17,240 --> 00:45:28,469 Edward Wilson-Ewing: and in particular, when you look at collapse models, you notice that there's an inner horizon that forms, and this is something which is missed in vacuum. And so this could be something that's important to 401 00:45:28,960 --> 00:45:46,970 Edward Wilson-Ewing: to include and to study. So to look at these collapse models, we decide just to start with the very simplest case which is the lemmite, toleman, bonnie space time. So these are spherically symmetric space times with a dust field. So this is pretty much the simplest collapse model that you can have. 402 00:45:46,980 --> 00:46:04,739 Edward Wilson-Ewing: and of course the goal is to eventually build towards more realistic things. Where you have matter fields which may be more, they capture more of the physics that you would expect that may be relevant during collapse. But a dust field is very simple, and it provides a very good starting point to study these questions. 403 00:46:05,900 --> 00:46:13,779 Edward Wilson-Ewing: There's been a lot of work studying black holes in quantum gravity and prom, and we should have both discussed some of those works. 404 00:46:14,930 --> 00:46:28,110 Edward Wilson-Ewing: What we did. Of course we built on everything that came before, and I think 3 of the key ingredients that we used was first. We wanted to Hamiltonian treatment to the full space time, so not just to focus on the interior, but everything all at once. 405 00:46:28,800 --> 00:46:38,159 Edward Wilson-Ewing: We also wanted to use the same improved dynamics that are used as in lu quantum cosmology, and we also wanted to include matter with local degrees of freedom. 406 00:46:38,490 --> 00:46:44,650 Edward Wilson-Ewing: So these were all things that had been considered separately. But I think that this was the first time with all these 407 00:46:44,780 --> 00:46:54,010 Edward Wilson-Ewing: things are put together for the first time. More recently there's also been some other work that's very complementary to this, and so we shouldn't talked about some of that. 408 00:46:55,870 --> 00:47:03,850 Edward Wilson-Ewing: So let me explain the main steps that we followed to study these collapse models. I'm going to skip a lot of the details just 409 00:47:03,910 --> 00:47:12,259 Edward Wilson-Ewing: for lack of time. But of course, if you have any questions, I'll be happy to answer them, and also all the details are included in the papers. 410 00:47:12,420 --> 00:47:13,359 Edward Wilson-Ewing: So 411 00:47:13,490 --> 00:47:19,799 Edward Wilson-Ewing: the first thing that we did was to start with classical Gr in the Hamiltonian framework and impose spherical symmetry. 412 00:47:20,910 --> 00:47:29,420 Edward Wilson-Ewing: Once we have that we have 2 constraints that are left. We have the scalar constraint and the radial. If You' more physical constraint, and we gauge, fix both of these 413 00:47:29,560 --> 00:47:48,120 Edward Wilson-Ewing: we use the dust field as a clock, so this gauge fixes the scalar constraint, and we gauge fix the diffusion constraint by using aerial gauge this is setting this pre-factor here to be X squared, and similarly getting this pre-factor review One is the when we use the dust time gauge. 414 00:47:48,490 --> 00:47:51,130 Edward Wilson-Ewing: So this is something which is done classically. 415 00:47:52,400 --> 00:47:56,480 Edward Wilson-Ewing: Then, once we have our resulting theory, we have one 416 00:47:56,710 --> 00:48:07,520 Edward Wilson-Ewing: true physical Hamiltonian that's left. This is exactly as Motion was saying. We've gotten rid of the constraints. We have one true physical Hamiltonian, still the classic level we discretize in the radial direction. 417 00:48:08,060 --> 00:48:13,850 Edward Wilson-Ewing: So this will allow us to proceed to the quantum theory more easily, with a finite number of degrees of freedom. 418 00:48:15,110 --> 00:48:17,420 Edward Wilson-Ewing: Then we do a loop quantization. 419 00:48:17,640 --> 00:48:24,870 Edward Wilson-Ewing: The economies that we want to look at are holonomy that travel along edges on the surface of a sphere. 420 00:48:25,040 --> 00:48:28,950 Edward Wilson-Ewing: So in this case Mubar turns out to be a coordinate, that is an angle. 421 00:48:29,530 --> 00:48:30,560 Edward Wilson-Ewing: And so 422 00:48:30,950 --> 00:48:39,170 Edward Wilson-Ewing: the input that we get from the improved dynamics is that we want the physical length of this edge to be equal to the plank length. Essentially. 423 00:48:40,310 --> 00:48:52,700 Edward Wilson-Ewing: And so if we want the length of this arc to be the plank length, and this is the arc of at some radius x, and that means that we have to choose an angle new bar, which is given by the plank length divided by X. 424 00:48:53,360 --> 00:49:00,870 Edward Wilson-Ewing: So once we make that choice that selects me bar for us, and then we can go ahead and do the standard loop quantization 425 00:49:00,980 --> 00:49:10,539 Edward Wilson-Ewing: again. As I said, we discretize along the readable coordinates. So at each node on the lattice. We can do loop quantization. They are using this. You've our scheme. 426 00:49:11,070 --> 00:49:16,519 Edward Wilson-Ewing: Once we have our quantum theory, we can get some effective dynamics. 427 00:49:16,620 --> 00:49:20,519 Edward Wilson-Ewing: This is still effective dynamics on this lattice that we introduced. 428 00:49:20,630 --> 00:49:23,109 Edward Wilson-Ewing: and then we take the continuum limit from that. 429 00:49:23,810 --> 00:49:30,420 Edward Wilson-Ewing: So this gives us an effective dynamics that describes a continuum 430 00:49:32,590 --> 00:49:34,500 Edward Wilson-Ewing: space time at this point. 431 00:49:34,620 --> 00:49:43,910 Edward Wilson-Ewing: Okay, so these are the main steps. As I said, I've skipped over a lot of technicalities here, but hopefully, this gives a a clear idea of the process that we followed. 432 00:49:46,010 --> 00:49:51,890 Edward Wilson-Ewing: Now I won't show you the effective equations in themselves. They're not especially illuminating. 433 00:49:51,950 --> 00:50:02,489 Edward Wilson-Ewing: but as usual. They're generated by Hamiltonian density, because now we have local degrees of freedom in the radial direction. Of course, our Hamiltonian is no longer global, but really is a local quantity. 434 00:50:03,790 --> 00:50:11,060 Edward Wilson-Ewing: Now it turns out that there is a class of solutions which is particularly simple. So these are the ones that we focused on first. 435 00:50:11,340 --> 00:50:15,460 Edward Wilson-Ewing: and those are the ones where you have this pre-factor here to be one. 436 00:50:15,900 --> 00:50:17,939 This is a consistent 437 00:50:17,980 --> 00:50:25,200 Edward Wilson-Ewing: class of of solutions that we get from the effective dynamics. It solves the equations of motion, and this type of solution is preserved dynamically. 438 00:50:25,290 --> 00:50:29,890 Edward Wilson-Ewing: So this really is a viable class of solutions 439 00:50:30,090 --> 00:50:33,929 Edward Wilson-Ewing: for the effective dynamics that we get. 440 00:50:34,490 --> 00:50:38,860 Edward Wilson-Ewing: There are other solutions out there also. They're more complicated. 441 00:50:39,360 --> 00:50:46,839 Edward Wilson-Ewing: That that's the topic of current work right now that we're looking at. But what i'll talk about today is really looking at this particular class of solutions. 442 00:50:47,560 --> 00:50:54,969 Edward Wilson-Ewing: which still, as we'll see, is very rich, and allows us to really study a wide range of collapse models. 443 00:50:56,010 --> 00:51:04,040 Edward Wilson-Ewing: Once we do this, we only have one variable left, which is B. So this is the component of the connection in angular directions. 444 00:51:04,560 --> 00:51:13,149 Edward Wilson-Ewing: and the dynamics which come from the Hamiltonian density are a this nonlinear wave equation which I show here. 445 00:51:13,730 --> 00:51:16,079 Edward Wilson-Ewing: The specific form is not so important. 446 00:51:16,620 --> 00:51:22,519 Edward Wilson-Ewing: What I really want you to see is that this is an equation of motion which comes from the effective dynamics. 447 00:51:22,780 --> 00:51:25,049 Edward Wilson-Ewing: and it's a nonlinear wave equation for B. 448 00:51:26,160 --> 00:51:29,610 You. You can see that there's the polymerization that occurs here. 449 00:51:30,010 --> 00:51:32,839 Edward Wilson-Ewing: But the main the main message 450 00:51:32,860 --> 00:51:37,109 Edward Wilson-Ewing: to take from here is really that we have a nonlinear wave equation. 451 00:51:38,800 --> 00:51:45,190 Edward Wilson-Ewing: and in general, when we have a nonlinear wave equation, then often it's necessary to look for week solutions. 452 00:51:46,210 --> 00:51:50,679 Edward Wilson-Ewing: So let me say a little bit about weak solutions before I come back and talk about the solutions that we find 453 00:51:50,760 --> 00:51:51,779 Edward Wilson-Ewing: to this. 454 00:51:52,060 --> 00:51:54,099 Edward Wilson-Ewing: Now, when you have 455 00:51:54,200 --> 00:51:55,709 a pde. 456 00:51:55,730 --> 00:52:05,480 Edward Wilson-Ewing: which is nonlinear. Then, As I said, we often have to look for week solutions, and these are solutions that are not differentiable. So, just by definition, they can't solve a differential equation. 457 00:52:05,730 --> 00:52:09,740 Edward Wilson-Ewing: But if you take your differential equation and you rewrite it as an integral equation. 458 00:52:09,770 --> 00:52:12,299 Edward Wilson-Ewing: then a weak solution can satisfy that. 459 00:52:12,370 --> 00:52:19,650 Edward Wilson-Ewing: So, for example, take a general conservation equation of this form, and integrate it with respect to both T. And X. 460 00:52:19,860 --> 00:52:25,180 Edward Wilson-Ewing: So here you have a time derivative so when you integrate with respect to T, you'll just get some boundary terms. 461 00:52:25,320 --> 00:52:27,840 Edward Wilson-Ewing: and then you integrate with X, and you have this integral here. 462 00:52:28,500 --> 00:52:35,319 Edward Wilson-Ewing: Similarly, you have the second term here. We integrate. With respect to X. You get boundary terms in terms of F here, and then you integrate with respect to T. 463 00:52:35,670 --> 00:52:39,359 Edward Wilson-Ewing: So you rewrite this Pde as an integral equation. 464 00:52:39,680 --> 00:52:40,899 Edward Wilson-Ewing: And now 465 00:52:41,040 --> 00:52:42,889 Edward Wilson-Ewing: it's possible for 466 00:52:42,940 --> 00:52:47,099 Edward Wilson-Ewing: functions you which are not differentiable to satisfy the interval equation. So 467 00:52:47,590 --> 00:52:50,649 Edward Wilson-Ewing: solutions of this type are known as week solutions. 468 00:52:51,150 --> 00:52:57,190 Edward Wilson-Ewing: and in some cases you get some week solutions which are actually discontinuous. And then the discontinuity is called a shock wave. 469 00:52:59,490 --> 00:53:01,910 Edward Wilson-Ewing: And just to 470 00:53:02,040 --> 00:53:16,109 Edward Wilson-Ewing: I I realize that in in gravity we're not used to looking at weak solutions, but the these have been considered in general relativity. So a simple example are the thin shell solutions that you get using Israel's Junction conditions as well as the Dr. To of Shock wave. 471 00:53:16,550 --> 00:53:26,379 Edward Wilson-Ewing: There's also been some work in the mathematical relativity, literature. Looking at Ltb. Space Times already classical Gr. That argues that week solutions should be considered in this context. 472 00:53:26,870 --> 00:53:29,470 Edward Wilson-Ewing: so it perhaps it's not too surprising 473 00:53:29,550 --> 00:53:33,870 Edward Wilson-Ewing: that week solutions would be relevant. Also, when we include fun and grab the effects. 474 00:53:33,950 --> 00:53:40,759 Edward Wilson-Ewing: So what we did is that we looked for week solutions to the nonlinear wave equation. I showed you earlier. 475 00:53:41,840 --> 00:53:51,199 Edward Wilson-Ewing: and in some cases for very simple configurations. You can use some analytical methods. And so we did that for a thin shell, and also an Oppenheimer Snyder collapse. 476 00:53:51,500 --> 00:53:53,109 Edward Wilson-Ewing: But 477 00:53:53,300 --> 00:54:02,800 Edward Wilson-Ewing: in general we really have to go to numerics. And so for that we use the garden of algorithm this is a well known algorithm that's used a lot, for example, in fluid dynamics 478 00:54:02,820 --> 00:54:07,999 Edward Wilson-Ewing: and essentially is very well suited to handle these nonlinear Pds. 479 00:54:09,240 --> 00:54:12,379 Edward Wilson-Ewing: Okay, so let me show you an example of what we get. 480 00:54:12,550 --> 00:54:15,470 This is 481 00:54:15,620 --> 00:54:32,140 Edward Wilson-Ewing: that so? The top plot shows the energy density. So this is something that looks a little bit like a star. We have a large energy density here, and then it gets smaller, and then eventually gets quite small here. So you have something that looks a little bit like starve some radius, something like this, with maybe some desk, a little bit of desk that remains outside 482 00:54:33,550 --> 00:54:38,350 Edward Wilson-Ewing: the bottom plot shows the outgoing null expansion. 483 00:54:38,510 --> 00:54:43,160 Edward Wilson-Ewing: And so this will go to 0 where there is a horizon. 484 00:54:43,680 --> 00:54:48,990 Edward Wilson-Ewing: So as I play the movie, this this this star will collapse. 485 00:54:49,070 --> 00:54:57,230 Edward Wilson-Ewing: So the the dust will fall inwards. This it will get larger inside, and Verizon will form, and eventually we will see that there is a bounce that happens. 486 00:54:57,440 --> 00:54:58,279 Edward Wilson-Ewing: So 487 00:54:58,430 --> 00:55:02,499 Edward Wilson-Ewing: let me just go back a little bit. So here 488 00:55:03,010 --> 00:55:20,019 Edward Wilson-Ewing: you can see that a horizon has formed outside. So we've been out of horizon. We have an inner horizon. The star is collapsing, and then, if I play that forward, the bounce happens, and we see a shock that forms after the bounce. So we have a discontinuity in the outgoing. All expansion and the energy density 489 00:55:20,030 --> 00:55:23,119 Edward Wilson-Ewing: of dust has become a very sharp pulse. 490 00:55:24,180 --> 00:55:25,029 Edward Wilson-Ewing: Okay. 491 00:55:25,820 --> 00:55:26,850 Edward Wilson-Ewing: So 492 00:55:27,250 --> 00:55:30,490 Edward Wilson-Ewing: that's one example. We did a lot of examples, and we found 493 00:55:30,570 --> 00:55:37,149 Edward Wilson-Ewing: very generally there's no singularity. It's replaced by a bounce. We find that a shock wave always forms at the latest at the Bam's time. 494 00:55:37,540 --> 00:55:52,609 Edward Wilson-Ewing: We also found that bounce is stable, so there are some issues that show up when you construct a non singular black holes, especially in the vacuum case. You can. You may have some mass, inflation, stability, or instability in falling matter for white holes, and neither of these is an issue 495 00:55:52,620 --> 00:56:06,350 Edward Wilson-Ewing: here. So everything is very stable. We also find a lifetime for the black hole from the formation of the outer horizon to its disappearance. When the shock wave exits which is proportional to the square of the Black Hole. Mass. 496 00:56:08,020 --> 00:56:09,560 Edward Wilson-Ewing: Okay. So 497 00:56:09,840 --> 00:56:29,009 Edward Wilson-Ewing: let me go back to the questions that I raised at the very beginning that the main points that we would like to address are the singularity and information loss, so as far as the singularity goes, in this specific model for black full collapse. It's very clear. There is no singularity. It's replaced by a non-singular bounce, and the formation of a shock. 498 00:56:29,390 --> 00:56:31,339 Edward Wilson-Ewing: What about information? Loss 499 00:56:31,610 --> 00:56:37,790 Edward Wilson-Ewing: well here this lifetime may be important, so we haven't 500 00:56:37,990 --> 00:56:42,670 Edward Wilson-Ewing: done as much concerning information loss. But we can say a little bit. 501 00:56:43,120 --> 00:56:51,479 Edward Wilson-Ewing: so we see that there's no singularity, and also there's no event. Horizon. There are apparent horizons, but these are only there for finite amount of time, and eventually go away. 502 00:56:52,690 --> 00:56:57,290 Edward Wilson-Ewing: So this to me already suggests that there's no information loss, because. 503 00:56:57,360 --> 00:57:04,499 Edward Wilson-Ewing: you know, at some point the current horizons are gone, and we should be able to recover the information, but we can actually make this a little bit more precise. So first. 504 00:57:04,560 --> 00:57:05,959 the 505 00:57:06,000 --> 00:57:12,739 Edward Wilson-Ewing: Lqg. Corrections at the horizon are extremely small, and are negligible. So hawking radiation will occur as usual. No changes there. 506 00:57:12,920 --> 00:57:16,699 Edward Wilson-Ewing: but the predicted lifetime is much shorter than the page time. 507 00:57:16,780 --> 00:57:24,679 Edward Wilson-Ewing: So what that means is that the entropy of the hawking radiation will always be much much smaller than the Black Hole entropy. 508 00:57:24,760 --> 00:57:29,319 Edward Wilson-Ewing: So in principle, at least, there's no problem with purifying hawking radiation at a later time. 509 00:57:29,850 --> 00:57:38,320 Edward Wilson-Ewing: So you have some a small amount of talking radiation which will presumably be entangled with matter or gravitational fields in the shock wave. 510 00:57:38,450 --> 00:57:45,959 Edward Wilson-Ewing: and these degrees of freedom will be accessible to outside observers. Once the apparent verizon vanishes after the shock has gone beyond the short-shield radius. 511 00:57:46,050 --> 00:57:59,409 Edward Wilson-Ewing: Now this is very much a sketch. There's a lot more work that's required to make this precise, and to show exactly how it may be possible to purify hawking radiation. But I think this gives us some hints and some directions for future research to really try and fill this gap. 512 00:58:00,400 --> 00:58:01,439 Edward Wilson-Ewing: So 513 00:58:01,620 --> 00:58:04,960 Edward Wilson-Ewing: I think i'm out of time. So i'll just put my 514 00:58:05,010 --> 00:58:23,420 Edward Wilson-Ewing: summary up here. There's, of course, a lot of other steps that need to be done. Perhaps the main limitation of the work I presented is the gauges that are fixed before quantizing, and i'm very encouraged to see if there's been some work that may avoid imposing these gauges instead by 515 00:58:23,750 --> 00:58:35,220 Edward Wilson-Ewing: cage, takes them with respect to matter, Field. So I think this is very complementary, and may be able to help, you know. Try some other complementary approaches, and see how similar the results are or not. 516 00:58:35,640 --> 00:58:52,870 Edward Wilson-Ewing: But the main question that I want to emphasize here is that I think it's very important to include hawking radiation, and hopefully, explicitly show how we can recover information from Black Hole and purify what hawking the hockey mediation that was emitted by the Black Hole. So let me stop here and thank you for your attention. 517 00:58:56,620 --> 00:59:02,290 Viqar Husain: Thanks to all the speakers we have. We're at 12. But let's have some 518 00:59:02,390 --> 00:59:03,569 Viqar Husain: questions, so 519 00:59:03,990 --> 00:59:05,260 please ask. 520 00:59:12,370 --> 00:59:13,740 Viqar Husain: Are they? Look for hands? Here 521 00:59:20,360 --> 00:59:21,569 LSU: I have a question. 522 00:59:25,440 --> 00:59:26,080 Viqar Husain: please. 523 00:59:27,570 --> 00:59:28,699 LSU: and up to be. 524 00:59:28,860 --> 00:59:32,140 LSU: This is a a question for it. 525 00:59:32,220 --> 00:59:41,229 LSU: and just a curiosity. And and and what is the size of the the radius of the of the of the mass collapsing the minimum right 526 00:59:41,350 --> 00:59:43,120 LSU: it reaches during the collapse. 527 00:59:43,690 --> 00:59:50,840 Edward Wilson-Ewing: so the minimum radius that it reaches. So let's do the simplest type where you have something which is approximately homogeneous 528 00:59:50,870 --> 00:59:52,189 Edward Wilson-Ewing: in terms of dust. 529 00:59:52,250 --> 00:59:59,700 Edward Wilson-Ewing: that then the minimum radius will be the cube root of the short shield radius times, the plank length squared. 530 01:00:02,310 --> 01:00:07,070 Edward Wilson-Ewing: This is actually the radius. This is exactly the radius where the kretchman scalar, which is the plank scale. 531 01:00:07,440 --> 01:00:08,829 Edward Wilson-Ewing: So it's not surprising. 532 01:00:11,750 --> 01:00:12,549 LSU: Thank you. 533 01:00:12,630 --> 01:00:13,520 Edward Wilson-Ewing: Yeah, you're welcome. 534 01:00:16,630 --> 01:00:21,169 Abhay Vasant Ashtekar: Okay, I raise my hand, but I guess you don't see it. 535 01:00:21,400 --> 01:00:25,450 Abhay Vasant Ashtekar: So I I got a couple of questions for LED. 536 01:00:25,600 --> 01:00:36,439 Abhay Vasant Ashtekar: The thing is that the hawking radiation that you know talking did, and other people did, and which which was kind of supposed to be thermal, that is more or less 537 01:00:37,100 --> 01:00:38,239 Abhay Vasant Ashtekar: at late times. 538 01:00:39,400 --> 01:00:44,350 Abhay Vasant Ashtekar: and what you I mean, the in other words, the termality is at late times. 539 01:00:44,400 --> 01:00:47,679 Abhay Vasant Ashtekar: So in your case, since 540 01:00:47,990 --> 01:00:50,319 Abhay Vasant Ashtekar: your lifetime is much much shorter than hawking 541 01:00:50,370 --> 01:00:51,390 Abhay Vasant Ashtekar: lifetime. 542 01:00:51,500 --> 01:00:54,159 Abhay Vasant Ashtekar: You never reach that in late time. 543 01:00:54,560 --> 01:00:57,910 Abhay Vasant Ashtekar: so it's not completely. It's not clear to me that 544 01:00:58,390 --> 01:01:04,080 Abhay Vasant Ashtekar: the this information loss issue is is going to be much more complicated to analyze in your case. 545 01:01:04,840 --> 01:01:10,019 Abhay Vasant Ashtekar: And but you know that people, I think Anderson, I think. 546 01:01:10,110 --> 01:01:14,810 Abhay Vasant Ashtekar: has really talked about corrections to the hawking. 547 01:01:15,100 --> 01:01:22,340 Abhay Vasant Ashtekar: the black body temperature at earlier time. So I think you should. It would be worth looking at that much, much more carefully 548 01:01:22,380 --> 01:01:24,109 Abhay Vasant Ashtekar: you start really going to be. 549 01:01:24,170 --> 01:01:27,040 Abhay Vasant Ashtekar: But also, I think the m squared. Is it that under 550 01:01:27,450 --> 01:01:31,409 Abhay Vasant Ashtekar: some tension from observations. M squared is being too small 551 01:01:31,730 --> 01:01:33,270 Abhay Vasant Ashtekar: for hawking radiation. 552 01:01:34,800 --> 01:01:36,339 Edward Wilson-Ewing: I'm not so anything about it. 553 01:01:36,940 --> 01:01:46,779 Edward Wilson-Ewing: Well, for for the first point I I agree. I I think this is something that I haven't really looked at any detail, and those corrections to formality could be very important. 554 01:01:46,910 --> 01:01:54,320 Edward Wilson-Ewing: especially because, as you say, this is at relatively small time scales compared to what Hawking was was considering. So that's definitely something to 555 01:01:54,350 --> 01:01:55,380 Edward Wilson-Ewing: to look at. 556 01:01:57,330 --> 01:02:00,230 Edward Wilson-Ewing: as far as the time scale goes. 557 01:02:00,530 --> 01:02:02,950 Edward Wilson-Ewing: Certainly M. Squared is 558 01:02:03,150 --> 01:02:12,360 Edward Wilson-Ewing: larger than the lifetime of of the universe since the Big Bang era. Right so as far as that goes, there are no issues for solar mass, black holes, or anything that ligo is seeing. 559 01:02:12,820 --> 01:02:15,380 Edward Wilson-Ewing: But I think that wasn't what you were worried about what? 560 01:02:15,920 --> 01:02:17,529 Abhay Vasant Ashtekar: No, I I I I just meant that 561 01:02:17,900 --> 01:02:19,129 Abhay Vasant Ashtekar: shouldn't we? 562 01:02:19,970 --> 01:02:25,250 Abhay Vasant Ashtekar: No; but I think there are that sort of must black holes, but that the other way around, namely, that that 563 01:02:25,640 --> 01:02:28,019 Abhay Vasant Ashtekar: black holes which are formed early on. 564 01:02:28,480 --> 01:02:36,750 Abhay Vasant Ashtekar: you know. Like it's like it's a small. It's a it's a it's a it's a 565 01:02:36,780 --> 01:02:39,659 Abhay Vasant Ashtekar: They should be exploding about now. 566 01:02:40,070 --> 01:02:51,239 Abhay Vasant Ashtekar: but if, on the other hand, you know, they should, exploding a long, long time ago for you. And so I think that they they should add some signatures of that around. 567 01:02:51,370 --> 01:02:52,450 Abhay Vasant Ashtekar: Yeah. So 568 01:02:52,880 --> 01:02:56,079 Abhay Vasant Ashtekar: So so. So so that that all the 569 01:02:56,460 --> 01:03:10,669 Edward Wilson-Ewing: right I'm: I'm: not a 100% sure about this. Because again, this is something I also haven't looked into in much detail. The first thing that I would say is that of course, this depends on the presence of primordial black holes. If there just aren't any, then, of course. 570 01:03:10,680 --> 01:03:17,040 Abhay Vasant Ashtekar: correct so. But then you you you'll put really strong constraints, which will put a lot of people out of business, if you like, and then 571 01:03:17,120 --> 01:03:24,379 Edward Wilson-Ewing: I I think we need to do more work before we can put in some constraints in that sense, because 572 01:03:24,550 --> 01:03:32,790 Edward Wilson-Ewing: the so let me just explain. When I first did this I was, I initially thought that there may be some signature from when the shock wave comes out of the horizon. 573 01:03:32,970 --> 01:03:38,899 Edward Wilson-Ewing: So let's say, there, there's some photons that are captured in the shock wave, the shockwave access to the rise, and then maybe these photons can now 574 01:03:38,920 --> 01:03:45,680 Edward Wilson-Ewing: travel freely, and we can see them, and this may be some sort of energetic event that we observe from a distance. 575 01:03:46,160 --> 01:03:50,270 Edward Wilson-Ewing: But then, if you look at it more closely. If the photons do start. 576 01:03:50,540 --> 01:03:51,349 Edward Wilson-Ewing: you know. 577 01:03:52,110 --> 01:03:53,779 Edward Wilson-Ewing: moving freely at that point. 578 01:03:53,870 --> 01:03:58,450 Edward Wilson-Ewing: there's still a very strong gravitational potential, and they'll be very strongly red, shifted. 579 01:03:58,880 --> 01:04:01,759 Edward Wilson-Ewing: And so at least that effect 580 01:04:01,840 --> 01:04:08,650 Edward Wilson-Ewing: doesn't seem to be easily observable now. There could be others that could in the shock way much after the horizon. 581 01:04:08,720 --> 01:04:09,699 Abhay Vasant Ashtekar: It can form 582 01:04:10,130 --> 01:04:12,310 Abhay Vasant Ashtekar: it. It. It goes out. 583 01:04:12,610 --> 01:04:16,720 Abhay Vasant Ashtekar: you know what. If so, that's where Red Shift might not be so hard, so high. There, isn't it. 584 01:04:16,790 --> 01:04:19,390 Edward Wilson-Ewing: Well, the the that the shock wave is still carrying mass. 585 01:04:19,950 --> 01:04:32,769 Edward Wilson-Ewing: So if if if let's say, the shock wave is just outside the horizon, let's say you know Schwarzschild plus some delta. Is that what happens? I I thought, that's real quick, and you, you know, can be very, very far away from them. 586 01:04:32,790 --> 01:04:40,579 Edward Wilson-Ewing: Yeah. So so so I think the question is, if if let's say, there are photons that are traveling with the shock wave, At what point do the photons leave the shock wave. 587 01:04:40,670 --> 01:04:53,690 Edward Wilson-Ewing: Do they leave it just when it access the horizon? Then the red shift will be very strong, but if they travel with the shock, they have a little bit longer before they leave it. Then the red shift could be smaller, and then there could be some observational effects. But but this is something I really have no idea about 588 01:04:54,360 --> 01:04:55,000 Yeah. 589 01:04:55,200 --> 01:04:57,529 Abhay Vasant Ashtekar: No one more question. Question. Okay. 590 01:04:57,560 --> 01:04:58,319 Abhay Vasant Ashtekar: Go ahead. 591 01:04:58,330 --> 01:05:27,850 Western: Can I interject just for a second it's a follow up from about this because of the case of the the phenomenology of an exploding like. So with lifetime. M. Square has been studied extensively by myself for alien Borrow and the students, so I don't so. Of course. Now I had this, considering the mechanism in which you have a shock wave, and I think the main difference with respect to what we have done before is the fact that you need a a white world. 592 01:05:28,070 --> 01:05:53,390 Western: a horizon basically to in what we were doing to have all the the matter coming out, but I think that the the constraints that we put to the constraints they were in in those series of papers from the last year. So we're already answering the kind of questions that the By. Was trying to rise. So I think there could be a complementarity between this all the literature and what I is doing now. 593 01:05:53,400 --> 01:05:55,310 Edward Wilson-Ewing: Yes, I think so, too. 594 01:05:55,670 --> 01:05:59,789 Viqar Husain: Can we go to Yuri? I think he had his hand up. Eric, please. 595 01:06:01,500 --> 01:06:17,620 Jerzy Lewandowski: Oh, thank you, I a I actually I have a some scattered and short questions to the E to the presentation. So there there was that in bookings. In the presentation there was that diagram 596 01:06:17,630 --> 01:06:26,109 Jerzy Lewandowski: in which a. A. Is is some Ds 2 times s 2 space time is separated from 597 01:06:26,340 --> 01:06:28,920 Jerzy Lewandowski: by some horizon, and 598 01:06:29,100 --> 01:06:32,170 Jerzy Lewandowski: and so my question is, isn't it? 599 01:06:32,190 --> 01:06:37,720 Jerzy Lewandowski: Hmm. Isn't. This a horizon extremal or on one side, and no external on the other side. 600 01:06:38,560 --> 01:06:39,439 Muxin Han: No. 601 01:06:39,630 --> 01:06:44,289 Muxin Han: no! The right from at the right, and it it looks just like classical 602 01:06:44,480 --> 01:06:46,279 Muxin Han: classical Schwarzschild space time 603 01:06:47,140 --> 01:07:07,040 Muxin Han: I see, so it's not. It's not the extreme All, even though it's not a spacetime inside. No, no, no, the yes, there, there's no there's no any quantum fact. Well, it's it's very. It's being extremely it's not quantum. It's also classical. It's just the different horizon. 604 01:07:07,410 --> 01:07:11,400 Muxin Han: Yeah, the the horizon. Just look at it. Looks very much like. 605 01:07:11,590 --> 01:07:17,140 Jerzy Lewandowski: yeah. But does it look the same on on, on, on on both sides. 606 01:07:17,200 --> 01:07:29,980 Muxin Han: so it doesn't have the same geometry when we look at it from the Ds 2 times it's 2 side. No from just 2. You don't really see this right, because this Ts 2 is really but infinity 607 01:07:30,040 --> 01:07:33,630 Muxin Han: is a scribe, and it's only a leave at a square plus. 608 01:07:36,130 --> 01:07:40,730 Muxin Han: And I'm asymptotically infinite as future. 609 01:07:42,090 --> 01:07:47,450 Jerzy Lewandowski: Okay. So what is in this region in this trapping trapping region? What what is it? 610 01:07:47,630 --> 01:07:49,100 Jerzy Lewandowski: Is it all? 611 01:07:49,830 --> 01:07:56,459 Abhay Vasant Ashtekar: It's a very complicated job it to which keeps oscillating and does all kinds of things. That's right. 612 01:07:56,620 --> 01:08:07,770 Jerzy Lewandowski: I see. And now why? Why? Why the horizon? Why, this killing horizon is not the event horizon. So so what is what is 613 01:08:08,070 --> 01:08:17,530 Muxin Han: right? It's just because it's it's there's no similarity, so it's. It's not a a standard. You know it's not not standard 614 01:08:17,540 --> 01:08:33,590 Muxin Han: a black hole. Space Time is but but event. Event. Horizon is defined by future of of the of of sky. So if also has a space like component. So I saw light from the inside goes out to the space like component. 615 01:08:33,609 --> 01:08:42,220 Abhay Vasant Ashtekar: But but then but the 1 point that mission sort of you. We discuss this in great detail, but what what you use of didn't play out with 616 01:08:42,660 --> 01:08:44,300 Abhay Vasant Ashtekar: that? I think it is a little bit 617 01:08:45,979 --> 01:08:54,480 Abhay Vasant Ashtekar: little bit imprecise to say that this space, like sky, is Ds 2 process 2, because it's 618 01:08:54,500 --> 01:09:00,199 Abhay Vasant Ashtekar: so. It's really become so. It's not really a boundary. And so. The questions that you like is asking 619 01:09:00,260 --> 01:09:04,709 Abhay Vasant Ashtekar: is, it is partially relevant because it's it's only 620 01:09:05,120 --> 01:09:17,919 Abhay Vasant Ashtekar: it's. It's all very close to that sky. You can say that value says to cross it, I see. So this is asymptotically, and and 1 one more question about this quantum region. So 621 01:09:17,930 --> 01:09:35,129 Jerzy Lewandowski: so you are so happy that you can extend the classical metric along this quantum vision. But but this is I I mean, what what is physically important? What is the stress energy tensor. So if you kind of calculate the Einstein tensor of this region, and think of this. 622 01:09:35,140 --> 01:09:51,670 Jerzy Lewandowski: It tensor classically as as team, you know. What is it? How is it? Is it? Oh, it's, it's it's it's it's it's complicated. So we we what is the size? I would worry about the size more and even level than 623 01:09:51,680 --> 01:10:04,260 Muxin Han: to side. Well, it's the size, the metric, you know, the the the entire space time Metric depend on some parameters, some free parameters, and the size of these space time is also is also a free parameter. 624 01:10:04,420 --> 01:10:09,409 Muxin Han: Of course you can't shrink this size inside the to be. There are 2 horizons. 625 01:10:09,500 --> 01:10:23,810 Muxin Han: and it's coming from your your space time. There are 2 horizons, so i'm the size of this B region cannot be inside these 2 horizons. It must be outside of it. So there is a lower bound basically distance between these 2 horizons. 626 01:10:23,960 --> 01:10:27,869 Muxin Han: But I mean, there's no in principle. There's no upper bound. 627 01:10:27,910 --> 01:10:31,449 Jerzy Lewandowski: And what is the curvature of the curvy? What is the curvature there? 628 01:10:31,710 --> 01:10:46,980 Muxin Han: The curvature? I'm. A part of it will be plunk in, I mean, because the in the Verizon and your spacetime. The unit Verizon is has plunking curvature, so which means in between the altar and in the horizon. And there's there's already a a plank in 629 01:10:47,130 --> 01:10:50,999 Muxin Han: regime, and then this regime extend to this B region 630 01:10:51,150 --> 01:10:54,739 Muxin Han: A part of the B region. It's: it's it's a plank in conversion. 631 01:10:55,330 --> 01:10:59,149 Viqar Husain: Okay, thank you. Okay, Good. Let's go to a a long in. 632 01:10:59,330 --> 01:11:00,860 Viqar Husain: I think that's the next 10, though. 633 01:11:04,140 --> 01:11:12,049 Erlangen: So hello, so so, so, so. So the point is like we can also use this the frequency matching model to study the vacuum case. 634 01:11:12,210 --> 01:11:23,090 Erlangen: but from that from the from the presentation of this 3 panelists. So it seems like if they go to this vacuum case, so we will get some in 635 01:11:23,310 --> 01:11:39,349 Erlangen: some different redoubt. So I want to ask those panelists. So what's what are their comments on this being consistency with each other, or what? As they created them to the other models. 636 01:11:43,480 --> 01:11:49,159 Viqar Husain: So if I understand the question, you're asking the panelists to criticize each other. Is that right? 637 01:11:49,380 --> 01:11:55,870 Erlangen: Yes, there is. There are all all the comments on this in consistency with each other. 638 01:11:56,190 --> 01:12:04,259 Viqar Husain: Oh, okay, so maybe, can you briefly give those comments? We have a couple of at least one other person asking questions. 639 01:12:04,710 --> 01:12:06,689 Okay. So for 640 01:12:06,870 --> 01:12:08,679 Viqar Husain: yeah. But go first. Yeah. 641 01:12:09,030 --> 01:12:10,209 psingh: I think like 642 01:12:10,620 --> 01:12:16,019 psingh: I I think that is the most important question right now. I I I think all of these 643 01:12:16,060 --> 01:12:17,480 psingh: 3 top show 644 01:12:17,840 --> 01:12:20,840 psingh: 3 different angles in which you approach the problem. 645 01:12:20,970 --> 01:12:21,719 and 646 01:12:22,030 --> 01:12:31,399 psingh: I do not fully understand what is the complete picture starting from a dynamical collapse and what will be inside, how relevant will be the group quantization of the 647 01:12:31,580 --> 01:12:38,790 psingh: course called Space Time at a later stage, or maybe it is going to give us many insights like this story is still unraveling. 648 01:12:38,860 --> 01:12:42,100 psingh: So I would say like it is premature to 649 01:12:42,430 --> 01:12:46,809 psingh: really answered that question. Now I I think we still need to understand 650 01:12:47,090 --> 01:12:58,280 psingh: many things, even in the dynamical case what motion has done, and we are one season AI space time that was seen earlier for the Boimer vendors load. We learned many lessons 651 01:12:58,460 --> 01:13:04,850 psingh: what LED is doing, is it's very encouraging. But there are issues of how we understand gauge, fixings, and so on. 652 01:13:05,130 --> 01:13:07,110 psingh: So I think it will 653 01:13:07,600 --> 01:13:14,560 psingh: not be. I I won't be wise to say, like, okay, this is the story, and this is the lesson for the dynamical picture. I think, like 654 01:13:15,040 --> 01:13:19,580 psingh: the bridges. There are still many bridges to be made, and this is a very complicated 655 01:13:19,600 --> 01:13:20,860 psingh: space-time. 656 01:13:21,070 --> 01:13:23,800 psingh: whichever way you look at it, and I think 657 01:13:24,620 --> 01:13:27,840 psingh: I don't know the final answer in this case. I'm: Sorry. 658 01:13:27,970 --> 01:13:30,330 Viqar Husain: Okay, machine, and then add very briefly. 659 01:13:30,710 --> 01:13:45,290 Muxin Han: So this is one of the reason why I I present tool stories. So so Firstly, this first story is about Covariance, right, and Covariance. We need to put some constraint on on the on the effective dynamics. Yeah, there are too many voices. 660 01:13:45,310 --> 01:13:59,409 Muxin Han: and one of the constraint is probably General Covariance. And here we show that, at least for for these effective, that them it's the general covariance. Is it is satisfied. Yeah. And then the second story is that how about we don't use effective dynamics? 661 01:13:59,640 --> 01:14:10,130 Muxin Han: Yeah. And we have we? We only consider something when we trust. And, for example, we we know a successful story about I to see, and and we know what 662 01:14:12,700 --> 01:14:29,690 Muxin Han: for Black Hole, and we know, and we have some symmetry considerations. We won't have some feeling semi-free somewhere in the space time and then yeah, there is a this the B region that is mystery, and then we can look at what kind of metrics that we can put it in. Yeah, and it's it's different from 663 01:14:29,700 --> 01:14:41,469 Muxin Han: It's mostly the physical considerations. Instead of computing effective equations for this, for this story. Yeah. And then we when if we 664 01:14:41,480 --> 01:14:53,880 Muxin Han: then we look at this spacetime, If this spacetime is, then we can I mean using these physical considerations to to select a good, effective dynamics? That is my comment. 665 01:14:54,110 --> 01:14:54,809 And 666 01:14:56,070 --> 01:14:59,570 Edward Wilson-Ewing: no, I I think a lot of already been said I, I think i'll just 667 01:14:59,830 --> 01:15:09,600 Edward Wilson-Ewing: essentially echo what both prom and mission have said, and maybe add that I think at this stage it's, you know. I think we're making progress in all of these directions. 668 01:15:09,860 --> 01:15:12,139 Edward Wilson-Ewing: and it would be foolish to 669 01:15:12,230 --> 01:15:21,110 Edward Wilson-Ewing: put all our eggs in one basket. So I think we need to keep on making progress in various directions, and each of these perspectives, I think, is complementary to the others. 670 01:15:21,130 --> 01:15:22,330 Edward Wilson-Ewing: and 671 01:15:22,390 --> 01:15:29,040 Edward Wilson-Ewing: ultimately, when once we figure it all out, I think we'll be taking ingredients from all of them. So I think all of these things need to be 672 01:15:29,260 --> 01:15:33,649 Edward Wilson-Ewing: are are very valuable, but also none of them are yet fully complete. 673 01:15:34,040 --> 01:15:34,880 Edward Wilson-Ewing: So 674 01:15:35,340 --> 01:15:40,049 Viqar Husain: good thanks. And we have one more question: is that sufficient there? 675 01:15:40,340 --> 01:15:41,080 Viqar Husain: Oh, yeah. 676 01:15:41,210 --> 01:15:42,280 Viqar Husain: question. 677 01:15:43,630 --> 01:15:48,699 Abhay Vasant Ashtekar: Can I just say this with 2 both things, small things. And answer to this question, please. 678 01:15:48,780 --> 01:15:53,890 Abhay Vasant Ashtekar: Yeah. So one thing is that I think in the Aos model. 679 01:15:54,870 --> 01:16:03,120 Abhay Vasant Ashtekar: but did not have enough time to talk about the exterior, but the metric is asymptotically flat, I mean, and and the idea of mass is well defined. 680 01:16:03,330 --> 01:16:10,139 Abhay Vasant Ashtekar: But still, but I quickly mentioned that the curvature does not dk as fast as it normally does 681 01:16:10,260 --> 01:16:11,170 Abhay Vasant Ashtekar: in the 682 01:16:12,120 --> 01:16:21,550 Abhay Vasant Ashtekar: in, in, in in classical gr. For a syndetically flat spacetime, and I think that in the exterior reason the kind of things that, for example, machine is doing. 683 01:16:21,700 --> 01:16:25,180 Abhay Vasant Ashtekar: bishing, and Hong Kong are doing in the 684 01:16:25,560 --> 01:16:27,750 in the exterior 685 01:16:27,950 --> 01:16:39,169 Abhay Vasant Ashtekar: for the vacuum case, that geometry and similar other geometries are all meadow and pull in, and that meaning have done in the exterior that geometry is probably better 686 01:16:39,260 --> 01:16:44,190 Abhay Vasant Ashtekar: than the a way geometry that came up. It will be good to understand the relation between the 2 687 01:16:44,570 --> 01:16:48,930 Abhay Vasant Ashtekar: in the interior region. On the other hand, I personally find that the 688 01:16:49,580 --> 01:16:55,210 Abhay Vasant Ashtekar: the the the thing that machine talked about in the interior job it to there 689 01:16:55,870 --> 01:17:10,750 Abhay Vasant Ashtekar: it's really not controlled, and we don't understand there are many aspects of physics there which I think are not completely understood when lots of detailed discussions about this. And so there i'm. Not so confident about this 690 01:17:10,970 --> 01:17:11,980 yup 691 01:17:12,190 --> 01:17:19,130 Abhay Vasant Ashtekar: whole bunch of bounces that occur, and all kinds of things that have occurred. Physical reason of that it's not completely. It's not at all clear to me. 692 01:17:19,160 --> 01:17:21,799 Abhay Vasant Ashtekar: So the future asymptotically, the setup of 693 01:17:21,910 --> 01:17:39,799 Abhay Vasant Ashtekar: up to some region inside the inside, the the the the first horizon. Everything is okay, but pushing and on. Go on do, but much later it doesn't seem to be very, very good. So there, I think one could take some lessons from some Aos model in the the pure vacuum case. 694 01:17:39,810 --> 01:17:42,260 Abhay Vasant Ashtekar: So I think that kind of complimentary, this sense. 695 01:17:43,810 --> 01:17:47,809 Viqar Husain: Okay, thanks, bye, we have one more question, vessel, please. 696 01:17:48,820 --> 01:17:50,180 Veso: Hey? Can you hear me. 697 01:17:50,430 --> 01:17:51,170 Viqar Husain: Yes. 698 01:17:52,870 --> 01:17:59,399 Veso: thank you. To all the our panelists and the moderator. It was very interesting. 699 01:17:59,430 --> 01:18:04,120 Veso: I need few qualifications from each of the speakers. 700 01:18:04,400 --> 01:18:11,140 Veso: For the first one. I I was wondering if you can just briefly remind me 701 01:18:11,240 --> 01:18:15,499 Veso: what is the Cnc. Bar, B+B bar? I assume P. 702 01:18:15,950 --> 01:18:19,449 Veso: C. And Tb. Are actually the momentum. But i'm not sure. 703 01:18:19,660 --> 01:18:23,230 Veso: That's my first question to 704 01:18:23,270 --> 01:18:24,469 Veso: on my 3 705 01:18:25,130 --> 01:18:29,219 Veso: and the second question for the second speaker. 706 01:18:30,290 --> 01:18:33,559 Veso: I wanna make sure I understand. So the idea that 707 01:18:33,600 --> 01:18:34,669 Veso: in the me 708 01:18:34,850 --> 01:18:36,999 Veso: gravity, when you up the desk 709 01:18:37,260 --> 01:18:42,210 Veso: effectively, you are removing the 710 01:18:42,520 --> 01:18:44,749 practically, you're fixing the gauge. 711 01:18:45,100 --> 01:18:46,899 Veso: If I understood correctly. 712 01:18:47,380 --> 01:18:51,699 Veso: and for the third one i'm not sure if I understand 713 01:18:51,720 --> 01:18:52,900 Veso: by 12 that 714 01:18:53,030 --> 01:19:01,559 Veso: basically the shock waves can out from the event horizon. Is that really possible? From physical point of view. If you have a black hole. 715 01:19:02,070 --> 01:19:05,960 Veso: so they These are my 3 questions, and I was appreciative. 716 01:19:06,250 --> 01:19:09,049 Veso: The speakers can quickly give me some qualifications. 717 01:19:09,650 --> 01:19:16,850 psingh: So if I understand the question correctly, you are asking what the Pb. And PC. Parts right? So they are the triads. 718 01:19:16,880 --> 01:19:19,110 psingh: and so PC. Is essentially 719 01:19:19,140 --> 01:19:24,360 psingh: the, and sits in front of the angular part of the metric, and it's equal to 4 M's. Care 720 01:19:24,530 --> 01:19:30,229 psingh: and the ratio of Pb. And PC. Comes in what will be the Gxx part? It doesn't have a 721 01:19:30,500 --> 01:19:31,150 Oh. 722 01:19:31,600 --> 01:19:35,660 psingh: as nice relationship, or something like Pb. Scale by PC. 723 01:19:36,410 --> 01:19:51,949 psingh: What about the C. And B. C and B are the momentas, or you can think of Cn, C and B are the 2 of the components of the 724 01:19:52,030 --> 01:19:59,649 psingh: they Are they? So the poison. Right? They are the conjugate variables. B. And Pv. And C. And PC. Are the conjugate variables. 725 01:20:01,170 --> 01:20:06,369 Veso: But physically it is not anything related to speed of light or anything like that. 726 01:20:06,530 --> 01:20:11,030 psingh: No, no, I'm sorry. Like the C. Has nothing to do with speed of light. That's just the connection component. 727 01:20:11,220 --> 01:20:12,550 psingh: I'm: Sorry. 728 01:20:12,640 --> 01:20:14,930 Viqar Husain: Yeah. We Shane? Briefly. 729 01:20:15,050 --> 01:20:30,140 Muxin Han: Yes, yeah. The answer is, you are. You are right. You are right. And so so the the Hamiltonian is based on the foliation of this internal time. 5. That's why I say, we say, this is a physical Hamiltonian. This is true, Hamiltonia instead of Hamiltonian constraint. 730 01:20:30,500 --> 01:20:33,900 Muxin Han: And so 731 01:20:34,790 --> 01:20:48,939 Edward Wilson-Ewing: yeah, so so that's right. So the shock really corresponds to discontinuity in the gravitational field. So you can ask, how is the shock moving with respect to the metric on the outside, and with respect to the metric on the inside. 732 01:20:49,080 --> 01:21:08,590 Edward Wilson-Ewing: and it turns out that the shock moves in a time like way with respect to the metric inside, but in the space like way with respect to the metric outside. So that is it inside the horizon. So you can think of this as being some sort of effective violation of the dominant energy condition which allows you to move in a space like way and eventually reach the outer horizon. 733 01:21:09,440 --> 01:21:14,730 Veso: Okay, but effectively, you cannot observe it, because there is a horizon between the 2 regions. 734 01:21:14,930 --> 01:21:18,990 Edward Wilson-Ewing: That's right. Yeah, at least outside of 735 01:21:19,190 --> 01:21:20,620 Veso: Yeah, thanks. 736 01:21:20,750 --> 01:21:21,609 Edward Wilson-Ewing: You're welcome. 737 01:21:22,750 --> 01:21:28,029 Viqar Husain: Okay. I don't see any other hands. Does anyone want to make any other comments? 738 01:21:31,100 --> 01:21:34,440 Viqar Husain: I'm just going to scan here? I don't see anything. So 739 01:21:34,590 --> 01:21:39,470 Viqar Husain: all right. Thank you to all the speakers and participants 740 01:21:40,230 --> 01:21:41,759 Viqar Husain: Very interesting discussion. 741 01:21:42,590 --> 01:21:44,359 Viqar Husain: and I think we can sign off. 742 01:21:44,560 --> 01:21:47,840 Viqar Husain: Do you have any other questions? You can just contact the speakers correctly. 743 01:21:50,430 --> 01:21:51,179 Viqar Husain: Thanks. 744 01:21:51,210 --> 01:21:53,489 Muxin Han: thanks, bye, bye, Thank you.