1 00:00:08,080 --> 00:00:11,279 Hello, and welcome to the Physics World weekly 2 00:00:11,279 --> 00:00:11,779 podcast. 3 00:00:12,160 --> 00:00:13,380 I'm Hamish Johnston. 4 00:00:14,384 --> 00:00:16,945 Earlier this autumn, I had the pleasure of 5 00:00:16,945 --> 00:00:18,804 visiting the Perimeter Institute 6 00:00:19,185 --> 00:00:22,565 for Theoretical Physics in Waterloo, Canada, 7 00:00:23,345 --> 00:00:25,285 where I interviewed four physicists 8 00:00:25,664 --> 00:00:26,804 about their research. 9 00:00:27,719 --> 00:00:30,140 This is the second of those conversations 10 00:00:30,679 --> 00:00:32,059 to appear on the podcast, 11 00:00:32,520 --> 00:00:34,859 and it's with Bianca Dietrich, 12 00:00:35,399 --> 00:00:38,219 whose research focuses on quantum gravity. 13 00:00:39,495 --> 00:00:42,234 Our chat is coming up after this message 14 00:00:42,454 --> 00:00:43,995 from IOP publishing, 15 00:00:44,454 --> 00:00:46,554 which brings you Physics World. 16 00:00:47,414 --> 00:00:50,475 Discover cutting edge science in minutes. 17 00:00:51,255 --> 00:00:54,795 IOP publishing's new progress in series 18 00:00:55,350 --> 00:00:57,210 Research Highlights website 19 00:00:57,670 --> 00:01:00,090 offers quick, accessible summaries 20 00:01:00,549 --> 00:01:03,289 of top papers from leading journals, 21 00:01:03,590 --> 00:01:06,090 like reports on progress in physics 22 00:01:06,390 --> 00:01:08,090 and progress in energy. 23 00:01:09,255 --> 00:01:12,055 Whether you're short on time or just want 24 00:01:12,055 --> 00:01:12,795 the essentials, 25 00:01:13,495 --> 00:01:16,694 these highlights help you expand your knowledge on 26 00:01:16,694 --> 00:01:17,674 leading topics. 27 00:01:18,855 --> 00:01:20,715 Perfect for busy researchers, 28 00:01:21,319 --> 00:01:24,840 curious minds, and anyone who wants to stay 29 00:01:24,840 --> 00:01:25,340 informed 30 00:01:25,719 --> 00:01:27,180 without the deep dive. 31 00:01:27,799 --> 00:01:29,739 To start reading, just type 32 00:01:30,120 --> 00:01:31,659 progress in series 33 00:01:32,200 --> 00:01:35,420 research highlights into your favorite search engine, 34 00:01:35,974 --> 00:01:38,454 or follow the link in the notes for 35 00:01:38,454 --> 00:01:39,275 this podcast. 36 00:01:41,494 --> 00:01:42,474 Albert Einstein's 37 00:01:42,775 --> 00:01:45,915 general theory of relativity does a great job 38 00:01:46,055 --> 00:01:47,354 at explaining gravity, 39 00:01:47,894 --> 00:01:49,994 but it is thought to be incomplete 40 00:01:50,579 --> 00:01:53,959 because it is incompatible with quantum mechanics, 41 00:01:54,420 --> 00:01:55,319 which itself 42 00:01:55,939 --> 00:01:57,239 is widely considered 43 00:01:57,700 --> 00:02:00,119 to be one of science's most successful 44 00:02:00,659 --> 00:02:01,159 theories. 45 00:02:02,259 --> 00:02:05,025 Developing a theory of quantum gravity is a 46 00:02:05,185 --> 00:02:06,724 crucial goal in physics, 47 00:02:07,105 --> 00:02:09,925 but it's proving to be extremely difficult. 48 00:02:10,625 --> 00:02:12,165 We discuss the challenges 49 00:02:12,705 --> 00:02:14,884 and the possible ways forward 50 00:02:15,344 --> 00:02:16,324 in this podcast. 51 00:02:24,840 --> 00:02:27,419 I'm at the Perimeter Institute in Waterloo, 52 00:02:27,719 --> 00:02:28,219 Ontario, 53 00:02:28,520 --> 00:02:31,224 and I'm very pleased to be joined by 54 00:02:31,224 --> 00:02:31,724 Bianca 55 00:02:32,104 --> 00:02:32,604 Dietrich. 56 00:02:33,224 --> 00:02:35,164 Hi, Bianca. Welcome to the podcast. 57 00:02:35,625 --> 00:02:38,125 Hi, Amish. Very nice talking to you. 58 00:02:38,985 --> 00:02:41,544 And, Bianca, we're going to talk about quantum 59 00:02:41,544 --> 00:02:42,044 gravity, 60 00:02:42,530 --> 00:02:45,009 which I have to admit is probably the 61 00:02:45,009 --> 00:02:45,509 one 62 00:02:45,969 --> 00:02:48,530 thing in physics that I know very little 63 00:02:48,530 --> 00:02:50,209 about. So you have you probably have to 64 00:02:50,209 --> 00:02:52,150 be very patient with me 65 00:02:52,449 --> 00:02:53,269 about this. 66 00:02:55,235 --> 00:02:57,094 So quantum gravity is is 67 00:02:57,875 --> 00:02:59,814 a very important field of research, 68 00:03:00,354 --> 00:03:03,395 particularly because we don't have a theory of 69 00:03:03,395 --> 00:03:05,254 quantum gravity, do we? So 70 00:03:05,794 --> 00:03:08,034 why don't we have one? Is why is 71 00:03:08,034 --> 00:03:08,935 it so difficult? 72 00:03:09,650 --> 00:03:11,030 Yeah. So that's correct. 73 00:03:11,569 --> 00:03:13,969 We possibly don't have a theory of quantum 74 00:03:13,969 --> 00:03:14,469 gravity 75 00:03:14,849 --> 00:03:17,270 that, you know, enough people are happy with. 76 00:03:17,409 --> 00:03:18,150 I don't know. 77 00:03:18,530 --> 00:03:21,250 And so there's a well, there's a number 78 00:03:21,250 --> 00:03:23,349 of reasons you might have to stop me. 79 00:03:24,835 --> 00:03:28,034 Gravity turns out is, is very different from 80 00:03:28,034 --> 00:03:29,575 the three other interactions. 81 00:03:30,275 --> 00:03:31,735 We know of the strong, 82 00:03:32,115 --> 00:03:32,615 interaction, 83 00:03:33,155 --> 00:03:34,135 the weak interaction, 84 00:03:35,715 --> 00:03:36,534 and the electromagnetic 85 00:03:36,835 --> 00:03:37,335 interaction. 86 00:03:40,469 --> 00:03:42,310 I mean, one big reason is that it 87 00:03:42,310 --> 00:03:44,810 has a much larger and more complicated, 88 00:03:45,430 --> 00:03:45,930 symmetry 89 00:03:46,629 --> 00:03:47,610 group. There's 90 00:03:47,950 --> 00:03:48,450 a, 91 00:03:49,189 --> 00:03:52,490 independence of, choice of coordinates or diffeomorphism 92 00:03:53,030 --> 00:03:53,530 group, 93 00:03:54,555 --> 00:03:57,134 compared to, you know, just kind of Poincare 94 00:03:57,194 --> 00:03:57,694 asymmetries 95 00:03:58,074 --> 00:03:58,574 and, 96 00:03:59,354 --> 00:03:59,594 and, 97 00:04:00,395 --> 00:04:01,215 gauge series 98 00:04:02,155 --> 00:04:04,655 gauge symmetries of particle physics. 99 00:04:06,340 --> 00:04:06,659 And, 100 00:04:07,219 --> 00:04:07,719 indeed, 101 00:04:08,259 --> 00:04:08,759 gravity 102 00:04:09,219 --> 00:04:09,719 conceptually 103 00:04:10,900 --> 00:04:11,400 is 104 00:04:11,699 --> 00:04:13,639 according to Einstein's theory 105 00:04:14,419 --> 00:04:16,919 about the geometry of space and time. 106 00:04:17,860 --> 00:04:19,800 And it turns out because of this 107 00:04:20,334 --> 00:04:22,735 kind of invariance and the coordinates, you know, 108 00:04:22,735 --> 00:04:23,634 which is not 109 00:04:23,935 --> 00:04:25,555 asymmetry the other interactions 110 00:04:26,334 --> 00:04:28,495 do have. So usually, we quantize them on 111 00:04:28,495 --> 00:04:30,435 a fixed space and time background. 112 00:04:31,615 --> 00:04:33,375 But in the case of gravity, we don't 113 00:04:33,375 --> 00:04:36,099 have a fixed space and time background. It's 114 00:04:36,099 --> 00:04:37,240 a dynamical entity. 115 00:04:38,339 --> 00:04:41,240 And so there are many deep conceptual questions. 116 00:04:41,939 --> 00:04:42,839 And in fact, 117 00:04:43,699 --> 00:04:46,199 it's that if we do have a quantum 118 00:04:46,259 --> 00:04:47,959 theory of of gravity, 119 00:04:48,555 --> 00:04:51,055 we do also expect that we will have 120 00:04:51,274 --> 00:04:53,615 a quantization of space and time. 121 00:04:54,555 --> 00:04:57,295 And so that would kind of completely change 122 00:04:58,394 --> 00:05:00,735 our notion of order space and time. 123 00:05:02,039 --> 00:05:04,699 It also shows us that we possibly 124 00:05:05,319 --> 00:05:08,379 well, we need possibly new quantization techniques. 125 00:05:09,240 --> 00:05:10,219 And in fact, 126 00:05:10,839 --> 00:05:13,419 we could not apply many of the techniques 127 00:05:13,560 --> 00:05:16,459 which are which we rely very heavily on 128 00:05:16,714 --> 00:05:19,275 in the case of standard quantum field theory, 129 00:05:19,275 --> 00:05:20,654 so for the other interactions. 130 00:05:22,795 --> 00:05:24,955 To give you some examples, we know that 131 00:05:24,955 --> 00:05:27,775 if we, you know, perturbative quantum field theories 132 00:05:27,835 --> 00:05:29,514 that was used for a long time to 133 00:05:29,514 --> 00:05:30,839 treat particle physics, 134 00:05:32,040 --> 00:05:33,740 This field, in the case of gravity, 135 00:05:34,839 --> 00:05:37,959 for for some technical reasons, usually is expressed 136 00:05:37,959 --> 00:05:38,779 as not renormalizable. 137 00:05:41,560 --> 00:05:44,759 Another example is that, what what we also 138 00:05:44,759 --> 00:05:45,555 use a lot 139 00:05:47,394 --> 00:05:50,134 for particle physics or for condensed matter 140 00:05:50,914 --> 00:05:52,214 is a a very, 141 00:05:53,794 --> 00:05:55,014 a trick which is 142 00:05:55,714 --> 00:05:56,454 very useful, 143 00:05:57,235 --> 00:05:58,790 and that's that we, 144 00:05:59,169 --> 00:05:59,669 rotate 145 00:06:00,129 --> 00:06:00,870 the time 146 00:06:01,329 --> 00:06:01,490 in, 147 00:06:02,290 --> 00:06:04,470 in the complex plane, the so called rotation. 148 00:06:06,129 --> 00:06:07,509 And that allows us, 149 00:06:08,250 --> 00:06:09,750 you know, that turns 150 00:06:10,185 --> 00:06:13,064 series where we have complex amplitudes in the 151 00:06:13,064 --> 00:06:13,805 sense of, 152 00:06:14,904 --> 00:06:17,564 amplitudes with the phase where we have interference 153 00:06:17,625 --> 00:06:20,605 and so on to turn into statistical amplitudes. 154 00:06:22,665 --> 00:06:23,064 And, 155 00:06:23,865 --> 00:06:25,884 that allows us to do Monte Carlo simulations. 156 00:06:28,080 --> 00:06:29,620 And, you know, QCD, 157 00:06:30,160 --> 00:06:31,779 well, is is more nonperturbative 158 00:06:32,160 --> 00:06:33,220 than, say, electromagnetisms, 159 00:06:33,600 --> 00:06:36,180 but to understand QCD, what do we do? 160 00:06:36,240 --> 00:06:38,580 Latest simulations versus Monte Carlo simulations. 161 00:06:39,754 --> 00:06:42,074 If you do not have access to to 162 00:06:42,074 --> 00:06:42,574 these, 163 00:06:42,954 --> 00:06:46,334 Monte Carlo simulations, for instance, we kind of 164 00:06:46,394 --> 00:06:48,475 get into problems which are also hard to 165 00:06:48,475 --> 00:06:50,014 solve in the case of QCD, 166 00:06:51,035 --> 00:06:51,754 which is kind of, 167 00:06:54,330 --> 00:06:56,009 if you if you do want to do 168 00:06:56,009 --> 00:06:58,410 real time simulations. So that is also a 169 00:06:58,410 --> 00:07:00,910 big issue in condensed matter and and QCD 170 00:07:01,370 --> 00:07:02,990 or the sign problem in QCD. 171 00:07:03,930 --> 00:07:06,650 And it is part of the problem also 172 00:07:06,650 --> 00:07:07,150 that 173 00:07:07,530 --> 00:07:08,415 we don't have 174 00:07:08,814 --> 00:07:09,314 experimental 175 00:07:10,095 --> 00:07:12,415 data. You can't test your theory by doing 176 00:07:12,415 --> 00:07:14,495 an experiment like you can in I mean, 177 00:07:14,495 --> 00:07:16,435 on one side matter or particle physics. 178 00:07:16,735 --> 00:07:18,415 You know, on one side, we have lots 179 00:07:18,415 --> 00:07:21,055 of experimental data because we know that's a 180 00:07:21,055 --> 00:07:21,795 road exists. 181 00:07:22,669 --> 00:07:23,649 I will come to that. 182 00:07:24,189 --> 00:07:26,910 But we don't have so much new input, 183 00:07:26,910 --> 00:07:30,610 which we cannot explain by the standard series. 184 00:07:31,389 --> 00:07:34,930 So it's really astonishing that, like, standard cosmology, 185 00:07:35,884 --> 00:07:37,884 you know, which, to some degree is is 186 00:07:37,884 --> 00:07:38,704 based on, 187 00:07:40,764 --> 00:07:43,024 linearized quantum field theory on curves based. 188 00:07:43,725 --> 00:07:44,544 We can explain 189 00:07:44,925 --> 00:07:46,544 lots of our observations 190 00:07:46,925 --> 00:07:48,365 in cosmology and that, 191 00:07:49,004 --> 00:07:50,845 even so we know, okay, there's a big 192 00:07:50,845 --> 00:07:51,504 bang and 193 00:07:52,370 --> 00:07:52,870 and, 194 00:07:53,410 --> 00:07:55,009 but we would need to go to higher 195 00:07:55,009 --> 00:07:57,889 order and perturbation theory, for instance, to to 196 00:07:57,889 --> 00:07:59,670 see effects from quantum gravity. 197 00:08:00,770 --> 00:08:03,810 So this is certainly true, but one example 198 00:08:03,810 --> 00:08:06,389 is that we have actually already observations, 199 00:08:07,694 --> 00:08:09,694 in the kind of Planck regime where we 200 00:08:09,694 --> 00:08:12,194 do where where some series, for instance, predicted 201 00:08:12,334 --> 00:08:13,634 that something could happen, 202 00:08:14,254 --> 00:08:16,654 in particular with regard to kind of Lorentz 203 00:08:16,654 --> 00:08:17,154 breaking 204 00:08:18,095 --> 00:08:20,495 and possible Lorentz deformation. And so there were 205 00:08:20,495 --> 00:08:21,060 kind of 206 00:08:21,459 --> 00:08:23,959 results from looking at gamma ray bursts, 207 00:08:24,579 --> 00:08:27,000 which are like gamma rays coming from 208 00:08:28,100 --> 00:08:30,120 sources which are very far away. 209 00:08:30,740 --> 00:08:33,639 And so there you have these gamma photons, 210 00:08:33,779 --> 00:08:35,480 which travel very long distances. 211 00:08:37,535 --> 00:08:39,295 And so the idea is there because they 212 00:08:39,295 --> 00:08:42,014 travel long distances, they have a long time 213 00:08:42,014 --> 00:08:45,295 to accumulate effects which come from having some, 214 00:08:45,295 --> 00:08:47,394 for instance, quantum space time. 215 00:08:49,259 --> 00:08:51,980 But the simplest models were basically ruled out. 216 00:08:51,980 --> 00:08:53,360 I mean, the kind of 217 00:08:54,059 --> 00:08:57,019 but the regime was indeed basically that they 218 00:08:57,019 --> 00:08:58,160 could already test 219 00:08:58,540 --> 00:08:59,759 planck scale physics. 220 00:09:01,179 --> 00:09:02,139 So that's certainly 221 00:09:05,235 --> 00:09:06,914 well, I mean, if you would have more 222 00:09:06,914 --> 00:09:07,894 of an experimental 223 00:09:09,075 --> 00:09:10,534 input, yeah, we 224 00:09:10,914 --> 00:09:13,654 possibly, that would reduce, the space of possibilities. 225 00:09:13,955 --> 00:09:14,355 And, 226 00:09:15,315 --> 00:09:17,634 I guess human fantasy is very large, so 227 00:09:17,634 --> 00:09:20,134 it's kind of many possibilities are explored. 228 00:09:22,080 --> 00:09:24,080 But I want to also express that, you 229 00:09:24,080 --> 00:09:26,340 know, quantum gravity is not useless. 230 00:09:28,800 --> 00:09:32,000 So I think first quantization attempts go back 231 00:09:32,000 --> 00:09:33,300 to the nineteen twenties. 232 00:09:34,404 --> 00:09:35,544 But an enormous 233 00:09:35,845 --> 00:09:36,745 part of 234 00:09:37,524 --> 00:09:39,865 what have became standard techniques 235 00:09:40,485 --> 00:09:41,785 in in modern physics 236 00:09:42,725 --> 00:09:44,745 has has started with the motivation 237 00:09:45,285 --> 00:09:46,904 of gravity or quantum gravity. 238 00:09:49,540 --> 00:09:51,779 You know, general relativity was the first example 239 00:09:51,779 --> 00:09:52,759 of a gauge theory. 240 00:09:53,540 --> 00:09:55,000 And so, like, 241 00:09:56,179 --> 00:09:58,600 techniques for the quantization of gauge theories 242 00:09:59,379 --> 00:10:00,120 were developed 243 00:10:00,420 --> 00:10:02,759 with, with motivation to do quantum gravity. 244 00:10:03,835 --> 00:10:05,934 The Newton Newton developed her 245 00:10:06,875 --> 00:10:08,335 formalism, the Newton serum, 246 00:10:09,434 --> 00:10:11,615 because she was asked by Herbert about gravity. 247 00:10:11,915 --> 00:10:13,774 So there are lots of examples. 248 00:10:15,529 --> 00:10:18,009 A more recent one is a topological phases 249 00:10:18,009 --> 00:10:19,149 in condensed matter. 250 00:10:19,850 --> 00:10:22,649 So first topological model was written down in 251 00:10:22,649 --> 00:10:23,690 1968 252 00:10:23,690 --> 00:10:25,070 by Pozano and Reggi 253 00:10:26,809 --> 00:10:28,485 as a mode, you know, as a model 254 00:10:28,485 --> 00:10:31,225 for, two plus one dimensional quantum gravity. 255 00:10:32,404 --> 00:10:35,445 And this kind of in recent years, well, 256 00:10:35,445 --> 00:10:37,925 variance of this model have become very popular 257 00:10:37,925 --> 00:10:39,785 in, in condensed matter. So 258 00:10:40,160 --> 00:10:43,299 there's lots of, ideas which were developed 259 00:10:44,720 --> 00:10:47,940 in the push to understand quantum gravity, which 260 00:10:48,480 --> 00:10:51,679 have become completely standard and, and and standard 261 00:10:51,679 --> 00:10:52,125 tools. 262 00:10:52,845 --> 00:10:54,684 And so I think I've worked for quantum 263 00:10:54,684 --> 00:10:56,784 gravity, but it's been a boon for physics. 264 00:10:56,924 --> 00:10:58,764 For, you know, for the for the larger 265 00:10:58,764 --> 00:10:59,664 physics community. 266 00:11:01,565 --> 00:11:03,965 And, indeed, you know, even me personally, I 267 00:11:03,965 --> 00:11:07,019 developed, like, tensor network tools, and we see 268 00:11:07,019 --> 00:11:07,519 the, 269 00:11:07,820 --> 00:11:10,399 like, also the difficulties in doing quantum gravity. 270 00:11:10,860 --> 00:11:12,799 So we try to understand it 271 00:11:13,179 --> 00:11:15,120 somewhat similar to condensed matter 272 00:11:16,220 --> 00:11:16,720 model. 273 00:11:17,179 --> 00:11:20,274 However, different from condensed matter, we would have 274 00:11:20,274 --> 00:11:23,254 to, bridge an enormous amount of scales 275 00:11:23,795 --> 00:11:25,554 that's kind of from the Planck scale, which 276 00:11:25,554 --> 00:11:28,115 is 10 to the minus 35 meters, which 277 00:11:28,115 --> 00:11:30,434 we do indeed do not have so much 278 00:11:30,434 --> 00:11:31,894 experimental access to 279 00:11:32,514 --> 00:11:34,774 to kind of the cosmos. 280 00:11:35,389 --> 00:11:36,210 So, basically, 281 00:11:36,990 --> 00:11:38,590 the idea would be to have a theory 282 00:11:38,590 --> 00:11:41,149 which is valid over all scales, which, you 283 00:11:41,149 --> 00:11:43,549 know, usually we don't have and which is 284 00:11:43,549 --> 00:11:44,690 a very hard problem. 285 00:11:46,190 --> 00:11:48,269 And there are many condensed matter models even 286 00:11:48,269 --> 00:11:50,575 in two dimensions, which we cannot solve. 287 00:11:51,514 --> 00:11:53,675 Like, the quantum gravity models we have, you 288 00:11:53,675 --> 00:11:55,995 know, they are far more complicated than con 289 00:11:56,075 --> 00:11:57,375 condensed matter models, 290 00:11:57,835 --> 00:11:58,975 like, four dimensions. 291 00:11:59,434 --> 00:12:01,295 We have to do them in real time. 292 00:12:01,355 --> 00:12:02,654 We cannot do the recoitation. 293 00:12:03,290 --> 00:12:04,110 So computationally, 294 00:12:04,570 --> 00:12:05,710 it's also an extremely 295 00:12:06,170 --> 00:12:08,990 hard problem. Mhmm. Yeah. We're kind of 296 00:12:09,610 --> 00:12:11,610 we don't have too many tools to do 297 00:12:11,610 --> 00:12:12,910 real time simulations, 298 00:12:13,370 --> 00:12:15,790 and we would need enormous computational 299 00:12:16,410 --> 00:12:16,910 power. 300 00:12:17,894 --> 00:12:19,975 And so maybe that will be in our 301 00:12:19,975 --> 00:12:21,995 future. Maybe we have quantum simulations, 302 00:12:23,254 --> 00:12:25,174 but these are some of the reasons. You 303 00:12:25,174 --> 00:12:27,174 know? So but then there's a push to 304 00:12:27,174 --> 00:12:28,794 develop computational tools, 305 00:12:29,269 --> 00:12:31,669 which was part of my research, and, you 306 00:12:31,669 --> 00:12:33,610 know, these are also useful for 307 00:12:34,230 --> 00:12:36,309 as a a port, like, just for condensed 308 00:12:36,309 --> 00:12:38,629 matter, for instance. And, Bianca, I wanted to 309 00:12:38,629 --> 00:12:40,710 ask you about your research here at the 310 00:12:40,710 --> 00:12:42,570 Perimeter Institute. You lead 311 00:12:43,269 --> 00:12:43,929 the from 312 00:12:44,414 --> 00:12:46,034 discretum to continuum 313 00:12:46,414 --> 00:12:46,914 initiative. 314 00:12:47,534 --> 00:12:49,475 What are the goals of this initiative? 315 00:12:50,495 --> 00:12:51,315 Yeah. So, 316 00:12:53,054 --> 00:12:55,695 the the discretum comes from the fact that, 317 00:12:57,559 --> 00:12:59,480 part of my research is about, 318 00:13:00,279 --> 00:13:00,779 nonperturbative 319 00:13:01,240 --> 00:13:02,779 models of quantum gravity, 320 00:13:03,559 --> 00:13:07,179 which often have discrete aspects. So they're either 321 00:13:07,720 --> 00:13:08,460 you start 322 00:13:09,000 --> 00:13:11,414 directly with kind of discrete building blocks. 323 00:13:13,334 --> 00:13:15,254 Then if it comes to spin forms or 324 00:13:15,254 --> 00:13:16,154 loop quantum gravity, 325 00:13:16,934 --> 00:13:19,334 it's in fact that discreteness is a kind 326 00:13:19,334 --> 00:13:21,014 of derived. It comes to the forms of 327 00:13:21,014 --> 00:13:21,514 formalism 328 00:13:21,975 --> 00:13:22,214 that, 329 00:13:23,254 --> 00:13:24,554 certain geometric quantities 330 00:13:25,095 --> 00:13:26,394 of discrete spectra. 331 00:13:27,580 --> 00:13:29,259 And so, in fact, you have also discrete 332 00:13:29,259 --> 00:13:30,080 building blocks. 333 00:13:31,179 --> 00:13:34,620 And then the big question is, well, it's 334 00:13:34,620 --> 00:13:37,340 it's very similar to to condensed matter, you 335 00:13:37,340 --> 00:13:38,320 know, where you have 336 00:13:39,035 --> 00:13:42,154 atoms or your your fundamental particles, and you 337 00:13:42,154 --> 00:13:43,055 try to understand 338 00:13:43,434 --> 00:13:45,355 the screw the interaction, you know, what is 339 00:13:45,355 --> 00:13:46,014 the material 340 00:13:47,355 --> 00:13:49,215 or who if you have water, 341 00:13:49,835 --> 00:13:51,509 eventually, you want to derive 342 00:13:52,549 --> 00:13:54,250 the flow equations for water. 343 00:13:54,870 --> 00:13:57,750 How does it behave? And so to get 344 00:13:57,750 --> 00:13:59,750 to the continuum limit to show that you 345 00:13:59,750 --> 00:14:00,250 get, 346 00:14:03,029 --> 00:14:05,590 well, space time as we know it, looking 347 00:14:05,590 --> 00:14:07,049 somewhat smooth and continuous. 348 00:14:08,235 --> 00:14:10,175 And so that is a is a 349 00:14:11,115 --> 00:14:12,254 aim of the initiative. 350 00:14:13,115 --> 00:14:15,215 That was in particular to to develop 351 00:14:16,154 --> 00:14:17,295 numerical methods, 352 00:14:18,634 --> 00:14:20,250 and we made progress there. 353 00:14:21,690 --> 00:14:24,009 But we made also recent progress in actually 354 00:14:24,009 --> 00:14:24,830 showing that, 355 00:14:26,009 --> 00:14:27,309 the spin forms which 356 00:14:28,009 --> 00:14:29,070 are mentioned there 357 00:14:29,450 --> 00:14:30,909 do indeed seem to have, 358 00:14:31,529 --> 00:14:33,284 a suitable continuum limits. 359 00:14:34,084 --> 00:14:36,904 Yeah. I wanted to ask you, Bianca, about 360 00:14:37,044 --> 00:14:39,065 spin foams. They sound intriguing. 361 00:14:40,164 --> 00:14:42,264 What what is a spin foam model, 362 00:14:42,644 --> 00:14:45,284 and, how could it provide insights into quantum 363 00:14:45,284 --> 00:14:45,784 gravity? 364 00:14:47,389 --> 00:14:49,970 So, yeah, spin forms come from an approach 365 00:14:50,190 --> 00:14:51,629 where we really take, 366 00:14:53,309 --> 00:14:55,490 Einstein's theory of general relativity 367 00:14:56,269 --> 00:14:57,009 as describing 368 00:14:58,509 --> 00:15:01,375 the gravitational interaction or the gravitational force as 369 00:15:01,375 --> 00:15:03,695 a property of space and time or the 370 00:15:03,695 --> 00:15:05,235 geometry of space and time. 371 00:15:06,254 --> 00:15:08,335 So we take this geometry of space and 372 00:15:08,335 --> 00:15:10,514 time as our dynamical field, 373 00:15:11,615 --> 00:15:12,115 and, 374 00:15:12,815 --> 00:15:14,434 this geometry is then quantized. 375 00:15:16,480 --> 00:15:19,059 And as a result of this procedure, 376 00:15:20,799 --> 00:15:22,179 it turns out that, 377 00:15:22,639 --> 00:15:24,100 indeed, as I mentioned, 378 00:15:24,639 --> 00:15:26,500 for instance, areas and volumes 379 00:15:27,065 --> 00:15:28,365 appear in in 380 00:15:29,304 --> 00:15:29,804 discrete 381 00:15:30,264 --> 00:15:32,424 this discrete spectra. So they kind of come 382 00:15:32,424 --> 00:15:33,804 all in little chunks. 383 00:15:34,504 --> 00:15:36,504 So that's the foam bit, the the little 384 00:15:36,504 --> 00:15:39,544 chunks? That's a foam bit. So the the 385 00:15:39,544 --> 00:15:40,470 the little chunks. 386 00:15:42,389 --> 00:15:44,809 And, basically, what the spin form 387 00:15:46,389 --> 00:15:48,889 model provides is an kind of a quantum 388 00:15:48,949 --> 00:15:49,449 amplitude 389 00:15:50,389 --> 00:15:51,529 for this chunk. 390 00:15:51,990 --> 00:15:54,889 More specifically, what is the geometry of this 391 00:15:55,189 --> 00:15:58,174 chunk? So probability amplitudes for 392 00:15:58,875 --> 00:16:00,495 how big this chunk is. 393 00:16:00,875 --> 00:16:02,315 And so that's one of these, 394 00:16:05,274 --> 00:16:06,235 aspects that, 395 00:16:06,875 --> 00:16:09,195 it's like how big and what is the 396 00:16:09,195 --> 00:16:10,575 scale of this chunk. 397 00:16:10,970 --> 00:16:13,450 But it's a dynamic variable, whereas usually in 398 00:16:13,450 --> 00:16:14,990 physics and all other 399 00:16:16,250 --> 00:16:19,450 quantum field series, it's something which we kind 400 00:16:19,450 --> 00:16:19,950 of, 401 00:16:21,610 --> 00:16:23,070 dial in from the outset. 402 00:16:23,930 --> 00:16:25,470 And so that's one of these 403 00:16:26,834 --> 00:16:29,414 interesting aspects which make it a bit challenging. 404 00:16:30,434 --> 00:16:33,014 But we have these amplitudes of each chunk, 405 00:16:33,875 --> 00:16:36,194 and the key difficulties then is to show 406 00:16:36,194 --> 00:16:39,314 that if we kind of consider lots and 407 00:16:39,314 --> 00:16:41,909 lots and lots and lots of these chunks, 408 00:16:44,069 --> 00:16:46,549 we do get something, you know, like a 409 00:16:46,549 --> 00:16:48,889 smooth space time with gravitational waves. 410 00:16:49,909 --> 00:16:51,610 So there is a kind of computational 411 00:16:52,069 --> 00:16:52,889 or as a, 412 00:16:55,289 --> 00:16:55,850 the the well, 413 00:16:56,389 --> 00:16:57,529 the key aim 414 00:16:58,125 --> 00:17:00,945 to to show and then to show also 415 00:17:01,565 --> 00:17:05,025 what would be effect effects behind having gravitational 416 00:17:05,164 --> 00:17:05,664 waves. 417 00:17:06,204 --> 00:17:07,585 I see. And 418 00:17:08,125 --> 00:17:10,445 you you're originally from Germany, but you've been 419 00:17:10,445 --> 00:17:14,069 associated with the Perimeter Institute for twenty two 420 00:17:14,069 --> 00:17:15,849 of its twenty five years. 421 00:17:17,269 --> 00:17:20,069 What initially attracted you to the institute, and 422 00:17:20,069 --> 00:17:21,369 and what does it offer 423 00:17:21,829 --> 00:17:22,789 physicists who, 424 00:17:23,670 --> 00:17:26,394 who are interested in quantum gravity? You can 425 00:17:26,394 --> 00:17:28,174 use this as a recruitment pitch 426 00:17:28,954 --> 00:17:31,355 for hiring new colleagues if you'd like. I 427 00:17:31,355 --> 00:17:33,994 I, you know, I came the first time 428 00:17:33,994 --> 00:17:35,694 as a as a PhD student, 429 00:17:37,194 --> 00:17:39,994 but with my supervisor, it's always good to 430 00:17:39,994 --> 00:17:42,679 be kind of spatially near to your supervisor. 431 00:17:43,059 --> 00:17:43,559 So, 432 00:17:44,819 --> 00:17:46,119 but I also heard 433 00:17:46,500 --> 00:17:49,619 at that point, Perimeter Institute was a very 434 00:17:49,619 --> 00:17:50,359 new institute, 435 00:17:50,740 --> 00:17:53,880 and, it was doing, you know, really research 436 00:17:53,940 --> 00:17:55,275 in quantum gravity, which 437 00:17:57,195 --> 00:17:59,674 well, certainly around 2003, 438 00:17:59,674 --> 00:18:01,755 I guess, was done only at very few 439 00:18:01,755 --> 00:18:02,255 places. 440 00:18:03,515 --> 00:18:04,015 And, 441 00:18:05,674 --> 00:18:06,894 well, even being 442 00:18:07,369 --> 00:18:09,950 quite young, I was already, like, very interesting 443 00:18:10,009 --> 00:18:12,509 people there in quantum in quantum gravity 444 00:18:12,970 --> 00:18:13,470 research. 445 00:18:14,730 --> 00:18:17,769 And so that also then motivated me, you 446 00:18:17,769 --> 00:18:19,309 know, to come back as a postdoc 447 00:18:20,714 --> 00:18:22,934 and to come back as a faculty. I 448 00:18:22,954 --> 00:18:24,394 mean, first of all, kind of, 449 00:18:25,674 --> 00:18:26,414 we have 450 00:18:26,954 --> 00:18:29,695 a we we are excellent in quantum gravity 451 00:18:29,755 --> 00:18:30,255 research. 452 00:18:32,474 --> 00:18:32,974 We 453 00:18:33,329 --> 00:18:33,829 have 454 00:18:34,450 --> 00:18:34,950 have 455 00:18:35,369 --> 00:18:35,869 a 456 00:18:36,289 --> 00:18:38,869 large group, excellent people. And, historically, 457 00:18:39,970 --> 00:18:40,470 indeed, 458 00:18:42,130 --> 00:18:44,609 from from 2001 459 00:18:44,609 --> 00:18:47,105 on, since since the institute was founded, 460 00:18:47,904 --> 00:18:48,565 we produced, 461 00:18:48,944 --> 00:18:51,585 like, lots of postdocs, which went on to 462 00:18:51,585 --> 00:18:54,244 be faculty in other places. So kind of, 463 00:18:55,105 --> 00:18:57,904 it's really center for quantum gravity research. But 464 00:18:57,904 --> 00:18:59,204 beyond that, we 465 00:19:00,029 --> 00:19:02,289 have lots of other theoretical physics 466 00:19:02,990 --> 00:19:03,490 directions. 467 00:19:04,430 --> 00:19:05,250 For instance, 468 00:19:06,430 --> 00:19:08,990 you know, in trying to develop numerical methods, 469 00:19:08,990 --> 00:19:11,625 I was interacting with condensed matter people here. 470 00:19:12,184 --> 00:19:13,325 There's strong gravity, 471 00:19:13,785 --> 00:19:16,744 which also there's lots of close interactions with 472 00:19:16,744 --> 00:19:18,285 quantum gravity or cosmology. 473 00:19:19,704 --> 00:19:21,625 So it's great to have all these different 474 00:19:21,625 --> 00:19:22,125 fields, 475 00:19:22,825 --> 00:19:23,325 because, 476 00:19:23,625 --> 00:19:25,500 you know, very interesting things happens 477 00:19:25,900 --> 00:19:27,680 happened at these intersections. 478 00:19:28,380 --> 00:19:30,480 I see. I mean, your your responsibilities 479 00:19:30,859 --> 00:19:33,500 here, do you I mean, primarily, you you 480 00:19:33,500 --> 00:19:35,500 do research. But do you do you do 481 00:19:35,500 --> 00:19:37,660 any teaching, you know, for example, at the 482 00:19:37,660 --> 00:19:40,220 University of Waterloo, or is is it mostly 483 00:19:40,220 --> 00:19:40,664 a 484 00:19:41,144 --> 00:19:41,644 a 485 00:19:42,025 --> 00:19:42,684 research position? 486 00:19:43,465 --> 00:19:45,725 Yeah. I'm research faculty, so, 487 00:19:47,384 --> 00:19:49,244 well, I don't kind of 488 00:19:49,545 --> 00:19:50,845 have to do teaching. 489 00:19:51,465 --> 00:19:52,125 I did 490 00:19:52,505 --> 00:19:53,309 I did talk 491 00:19:53,950 --> 00:19:56,130 in in the in the outside master 492 00:19:56,990 --> 00:19:58,750 course, also at some point at AIMS in 493 00:19:58,750 --> 00:20:00,990 Africa. So I, I did it a couple 494 00:20:00,990 --> 00:20:01,570 of times. 495 00:20:03,309 --> 00:20:05,865 Currently, I'm also faculty chair, so kind of 496 00:20:05,865 --> 00:20:07,884 busy with There's lots of administration. 497 00:20:08,585 --> 00:20:09,644 It was administration 498 00:20:10,265 --> 00:20:10,765 things. 499 00:20:11,865 --> 00:20:12,684 And so 500 00:20:13,305 --> 00:20:14,684 yeah. So there's kind of 501 00:20:16,025 --> 00:20:17,805 some teaching we do on, 502 00:20:18,730 --> 00:20:19,230 on 503 00:20:20,009 --> 00:20:22,329 on particular master on a master basis and 504 00:20:22,329 --> 00:20:23,630 PhD level basis. 505 00:20:24,890 --> 00:20:25,630 But, otherwise, 506 00:20:27,369 --> 00:20:29,149 it's very focused on on research. 507 00:20:30,250 --> 00:20:32,654 And and finally, we talked a bit about 508 00:20:32,894 --> 00:20:33,634 the difficulty 509 00:20:34,894 --> 00:20:35,795 of getting 510 00:20:36,174 --> 00:20:39,615 data, experimental data on quantum gravity. You mentioned 511 00:20:39,615 --> 00:20:41,934 the Planck scale and, you know, having to 512 00:20:41,934 --> 00:20:44,575 think about photons travelling across the universe to 513 00:20:44,734 --> 00:20:46,595 Yep. But to maybe see 514 00:20:46,974 --> 00:20:47,474 something. 515 00:20:49,410 --> 00:20:51,970 Does that discourage you sometimes when you're when 516 00:20:51,970 --> 00:20:54,309 you're doing your theoretical work? Or 517 00:20:54,609 --> 00:20:56,289 do you do you I suppose you have 518 00:20:56,289 --> 00:20:58,369 to have faith in the mathematics. Do you? 519 00:20:58,369 --> 00:21:00,855 Is that Yeah. I guess it depends. It's 520 00:21:00,934 --> 00:21:03,414 it's possibly, you know, different generations have different 521 00:21:03,414 --> 00:21:03,914 expectations. 522 00:21:05,095 --> 00:21:05,595 So, 523 00:21:07,734 --> 00:21:10,214 I'm possibly coming from a generation which is 524 00:21:10,214 --> 00:21:12,855 possibly okay. It takes a long time to 525 00:21:12,855 --> 00:21:15,255 kind of do quantum gravity, maybe, like, twenty 526 00:21:15,255 --> 00:21:16,380 years before me. People 527 00:21:17,339 --> 00:21:17,920 are expecting 528 00:21:18,619 --> 00:21:20,079 the solve it in ten years. 529 00:21:20,779 --> 00:21:23,259 Well, there's certainly always a certain level of 530 00:21:23,259 --> 00:21:23,759 excitement, 531 00:21:24,859 --> 00:21:28,240 about upcoming experiments. So as I mentioned, indeed, 532 00:21:29,305 --> 00:21:31,164 where there's kind of a number of proposals 533 00:21:31,384 --> 00:21:31,884 to, 534 00:21:33,465 --> 00:21:34,924 to measure things. 535 00:21:35,625 --> 00:21:38,105 Are are there any upcoming experiments that you're 536 00:21:38,105 --> 00:21:40,105 really excited about, or or have you been 537 00:21:40,105 --> 00:21:42,079 involved in any proposals? 538 00:21:43,259 --> 00:21:45,259 I well, I have not been so I 539 00:21:45,259 --> 00:21:47,440 mean, I've coming from a more theoretical, 540 00:21:48,619 --> 00:21:49,980 directional sense of, 541 00:21:50,700 --> 00:21:53,019 for spin for models, a key aspect for 542 00:21:53,019 --> 00:21:55,065 us was to show that, you know, we 543 00:21:55,065 --> 00:21:55,784 get to, 544 00:21:56,744 --> 00:21:58,524 a smooth space time, which, 545 00:22:00,664 --> 00:22:02,845 you know, actually well, if I can 546 00:22:03,464 --> 00:22:06,284 say why why would that be a key 547 00:22:07,000 --> 00:22:08,779 He said it is, that 548 00:22:09,799 --> 00:22:12,619 this was tried very often with various models, 549 00:22:14,759 --> 00:22:17,480 but most models use this idea of a 550 00:22:17,480 --> 00:22:19,900 weak quotation, so so called Euclidean models. 551 00:22:21,184 --> 00:22:23,984 And also, you start with four dimensional building 552 00:22:23,984 --> 00:22:25,664 blocks. It turned out if you try to 553 00:22:25,664 --> 00:22:27,445 glue them together into simulations, 554 00:22:28,545 --> 00:22:29,684 statistical simulations, 555 00:22:30,945 --> 00:22:33,345 most of the resulting structures you saw at 556 00:22:33,345 --> 00:22:34,325 larger scales 557 00:22:35,289 --> 00:22:37,930 didn't look at all like smooth manifolds. So 558 00:22:37,930 --> 00:22:40,330 they looked like fractals, for instance. So we 559 00:22:40,410 --> 00:22:42,430 actually, technically, they're called like polymers. 560 00:22:44,730 --> 00:22:46,670 And so that's happened for for 561 00:22:48,424 --> 00:22:50,825 twenty years. So it was only recently we 562 00:22:50,825 --> 00:22:51,565 we see, 563 00:22:52,345 --> 00:22:54,265 we have one model where this does not 564 00:22:54,265 --> 00:22:55,545 happen. So it's kind of, 565 00:22:56,025 --> 00:22:56,765 what be 566 00:22:57,224 --> 00:22:59,164 a key aspect to show non perturbatively 567 00:22:59,465 --> 00:23:01,244 that we get a smooth space time. 568 00:23:01,940 --> 00:23:03,079 However, I made 569 00:23:03,779 --> 00:23:06,339 a particular progress with spin forms in a 570 00:23:06,339 --> 00:23:07,400 more perturbative 571 00:23:08,259 --> 00:23:09,640 approach, so kind of, 572 00:23:10,980 --> 00:23:12,839 and we could show that we get, 573 00:23:13,884 --> 00:23:16,045 a gravitational waves. Assuming that we get a 574 00:23:16,045 --> 00:23:18,045 smooth space time, we do get we can 575 00:23:18,045 --> 00:23:20,304 show that we have gravitational waves, 576 00:23:20,765 --> 00:23:23,345 and we get also corrections to the dynamics 577 00:23:23,565 --> 00:23:24,065 compared 578 00:23:25,164 --> 00:23:26,464 to general relativity. 579 00:23:27,589 --> 00:23:29,829 So I'm kind of in the process indeed 580 00:23:29,829 --> 00:23:30,329 to 581 00:23:30,869 --> 00:23:32,170 think about experiments. 582 00:23:32,549 --> 00:23:34,329 No. That's it. So so are those 583 00:23:34,630 --> 00:23:37,029 those deviations, are they something that could be 584 00:23:37,029 --> 00:23:37,849 seen by 585 00:23:38,309 --> 00:23:41,305 LIGO or maybe a future experiment? To do 586 00:23:41,305 --> 00:23:41,884 the calculations. 587 00:23:42,265 --> 00:23:43,945 Right. But that would be a you know, 588 00:23:43,945 --> 00:23:45,484 that would be, interest 589 00:23:45,785 --> 00:23:48,285 some some things to to explore. 590 00:23:49,865 --> 00:23:51,465 It's actually also turns out that, 591 00:23:53,065 --> 00:23:55,305 you know, spin forms are technically kind of 592 00:23:55,384 --> 00:23:55,884 it's 593 00:23:56,950 --> 00:23:59,130 in principle, is a penalty violating 594 00:23:59,750 --> 00:24:01,990 theory if a certain parameter is not has 595 00:24:01,990 --> 00:24:04,250 not a very particular value. And so 596 00:24:05,029 --> 00:24:06,490 this is something which 597 00:24:07,190 --> 00:24:09,990 could provide more of an experimental signature because 598 00:24:09,990 --> 00:24:11,674 everything else is not penalty 599 00:24:12,134 --> 00:24:12,634 violating. 600 00:24:13,095 --> 00:24:13,595 So, 601 00:24:14,375 --> 00:24:16,375 on the other hand, it's very constraining, so 602 00:24:16,375 --> 00:24:17,515 I can see that. 603 00:24:18,295 --> 00:24:20,075 But there's, of course, many other 604 00:24:20,855 --> 00:24:23,755 ideas and and and proposals 605 00:24:24,420 --> 00:24:26,440 of of experimental signatures 606 00:24:27,860 --> 00:24:28,259 that, 607 00:24:28,740 --> 00:24:29,320 are always 608 00:24:30,340 --> 00:24:33,619 seem to be very promising. And, so, and 609 00:24:33,619 --> 00:24:37,000 that indeed includes gravitational waves or probing, 610 00:24:39,015 --> 00:24:40,794 probing's a big bang via cosmology. 611 00:24:41,974 --> 00:24:43,894 So has that I mean, with the, you 612 00:24:43,894 --> 00:24:45,434 know, discovery of gravitational 613 00:24:45,734 --> 00:24:48,534 waves and also, yeah, I suppose the information 614 00:24:48,534 --> 00:24:50,294 that we have, you know, from the cosmic 615 00:24:50,294 --> 00:24:51,835 microwave background, etcetera, 616 00:24:53,140 --> 00:24:53,460 You know, the 617 00:24:54,259 --> 00:24:55,880 I suppose these really amazing 618 00:24:56,660 --> 00:24:57,160 measurements 619 00:24:57,619 --> 00:24:59,619 Mhmm. Are they I mean, is that something 620 00:24:59,619 --> 00:25:02,099 that peep people who work on quantum gravity 621 00:25:02,099 --> 00:25:04,740 are very excited about? Is this possibly opening 622 00:25:04,740 --> 00:25:05,559 up a new 623 00:25:05,974 --> 00:25:07,815 view on the universe that could be very 624 00:25:07,815 --> 00:25:10,394 useful to you? I mean, it's certainly certainly 625 00:25:10,455 --> 00:25:12,215 that's what we hope. You know, on the 626 00:25:12,215 --> 00:25:14,394 technical side, and the, you know, the gravitational 627 00:25:14,535 --> 00:25:15,515 wave observations 628 00:25:16,134 --> 00:25:18,089 are also highly technical in itself. 629 00:25:19,130 --> 00:25:21,609 So there needs to be, well, some people 630 00:25:21,609 --> 00:25:22,429 which bridge, 631 00:25:22,970 --> 00:25:26,029 like, the theoretical chronology side to the observational 632 00:25:26,250 --> 00:25:26,750 side 633 00:25:27,289 --> 00:25:29,710 because there are many questions about about noise. 634 00:25:30,184 --> 00:25:30,924 No. But, 635 00:25:31,384 --> 00:25:31,884 physically, 636 00:25:32,265 --> 00:25:34,285 you know, there's this idea where, 637 00:25:37,304 --> 00:25:39,005 yeah, for instance, with a cosmological 638 00:25:39,625 --> 00:25:41,644 microwave background, so the elect 639 00:25:42,194 --> 00:25:42,694 electromagnetic 640 00:25:43,460 --> 00:25:45,080 radiation with electromagnetic 641 00:25:46,580 --> 00:25:48,119 electromagnetic radiation, we can probe 642 00:25:50,820 --> 00:25:53,559 early universe cosmology only so far 643 00:25:54,019 --> 00:25:56,724 because we need well, it's only after, you 644 00:25:56,724 --> 00:25:59,944 know, electromagnetic radiation decoupled from everything else. 645 00:26:01,444 --> 00:26:04,244 Whereas this, kind of if we could, like, 646 00:26:04,244 --> 00:26:05,625 gravitational wave background, 647 00:26:06,484 --> 00:26:08,964 that goes much further to the towards the 648 00:26:09,284 --> 00:26:11,284 Oh, I see. Yeah. The big bang. So 649 00:26:11,284 --> 00:26:12,450 you would expect to 650 00:26:13,649 --> 00:26:15,669 see much deeper to towards 651 00:26:15,970 --> 00:26:17,269 the beginning of the universe, 652 00:26:17,649 --> 00:26:19,889 the beginning of time. And so would that 653 00:26:19,889 --> 00:26:23,109 take you into a regime where quantum gravity 654 00:26:23,730 --> 00:26:26,289 was significant in terms of the evolution More 655 00:26:26,369 --> 00:26:29,923 of the universe. Certainly more significant. Right. So 656 00:26:30,017 --> 00:26:31,112 kind of 657 00:26:31,800 --> 00:26:32,634 yeah. So 658 00:26:34,315 --> 00:26:34,815 and, 659 00:26:35,914 --> 00:26:36,734 yeah, certainly 660 00:26:37,115 --> 00:26:37,855 more significant 661 00:26:38,154 --> 00:26:39,215 and, with, 662 00:26:39,914 --> 00:26:40,894 this kind of 663 00:26:41,195 --> 00:26:42,174 now also microwave 664 00:26:43,035 --> 00:26:45,539 measurements, which hopefully at some point, 665 00:26:46,480 --> 00:26:47,140 we could 666 00:26:47,840 --> 00:26:49,380 see nonlinear effects. 667 00:26:50,160 --> 00:26:52,100 And also for the nonlinear effects, 668 00:26:52,559 --> 00:26:55,059 we would see the quantum gravity would play 669 00:26:55,440 --> 00:26:57,039 more of a role than form of the 670 00:26:57,039 --> 00:26:58,180 linear linear 671 00:26:58,985 --> 00:27:01,965 things. And, there are also predictions of 672 00:27:03,225 --> 00:27:06,825 kind of predictions of, yeah, deviations for the 673 00:27:06,825 --> 00:27:07,725 linear theory, 674 00:27:08,904 --> 00:27:11,085 like the tilt of the spectrum and, 675 00:27:12,609 --> 00:27:15,089 which currently my understanding, you know, we cannot 676 00:27:15,089 --> 00:27:16,789 distinguish these effects, but, 677 00:27:17,170 --> 00:27:19,569 hopefully, in the future, we will. Oh, wow. 678 00:27:19,569 --> 00:27:21,730 So that well, that's really exciting then. I, 679 00:27:22,210 --> 00:27:23,890 I mean, I suppose my view of quantum 680 00:27:23,890 --> 00:27:26,049 gravity has always been, well, they'll never get 681 00:27:26,049 --> 00:27:28,815 any experimental data. I mean, it sounds like 682 00:27:28,954 --> 00:27:30,974 there could be lots coming through the pipeline. 683 00:27:31,755 --> 00:27:33,914 Yeah. So so we you always hope that 684 00:27:33,914 --> 00:27:34,414 this 685 00:27:34,714 --> 00:27:37,355 people will always predict some things. Yeah. Well, 686 00:27:37,355 --> 00:27:39,660 that Yeah. That's great. Thanks so much for 687 00:27:39,660 --> 00:27:41,980 explaining that to us, Bianca. And, best of 688 00:27:41,980 --> 00:27:43,759 luck with your research in the future. 689 00:27:44,220 --> 00:27:45,900 Thank you. It was nice to talk to 690 00:27:45,900 --> 00:27:46,400 you. 691 00:27:54,345 --> 00:27:56,125 That was Bianca Dietrich 692 00:27:56,585 --> 00:27:59,164 who spoke to me at the Perimeter Institute 693 00:27:59,625 --> 00:28:01,244 for Theoretical Physics. 694 00:28:01,865 --> 00:28:04,044 Thanks to Bianca for a fascinating 695 00:28:04,505 --> 00:28:05,005 conversation 696 00:28:05,544 --> 00:28:07,085 about quantum gravity. 697 00:28:07,730 --> 00:28:10,369 And a special thanks to our producer Fred 698 00:28:10,369 --> 00:28:10,869 Ailes. 699 00:28:11,570 --> 00:28:14,049 We'll be back again next week. See you 700 00:28:14,049 --> 00:28:14,549 then.