1 00:00:00,410 --> 00:00:09,960 Okay. Okay, folks, we can probably start today with allies and friends on the topic and minorities. 2 00:00:11,370 --> 00:00:17,040 Minorities. Our president is due to have that where you said his position before that mean 3 00:00:17,490 --> 00:00:22,380 their undergraduate degree in Athens they at Stanford University introduced 4 00:00:22,500 --> 00:00:27,660 interestingly enough first couple of issues at Stanford he was in my late seventies 5 00:00:27,870 --> 00:00:31,980 and married and then relation although I just go to temptation oversaw the life 6 00:00:34,350 --> 00:00:39,759 that wasn't too long ago very committed to UC Berkeley and not actually that 7 00:00:39,760 --> 00:00:43,319 happens for a post and then went to a senior position at Stanford is that most 8 00:00:43,320 --> 00:00:47,969 recently to get the completed appointments did a minor amenities very famous 9 00:00:47,970 --> 00:00:53,790 Nobel for having really no thoughts at the forefront of young cerebral physics, 10 00:00:54,000 --> 00:00:58,410 particularly thinking about new ways of investigating programmable physics, 11 00:00:58,440 --> 00:01:03,360 new ways of detecting very light particles, new particles in various ways with atoms and clocks. 12 00:01:03,360 --> 00:01:08,370 And that moved from a tree. And she kept us going baffled as to what was going on. 13 00:01:09,630 --> 00:01:13,230 Oh, thank you, John. I should say it's great to be back. 14 00:01:13,230 --> 00:01:20,130 I've actually spent a large part of my time as an and as a graduate student here in Oxford in the summer. 15 00:01:20,490 --> 00:01:24,390 And I have very fond memories of Oxford, have great physics. 16 00:01:24,450 --> 00:01:27,150 We did great physics here and it's good to be back. 17 00:01:27,750 --> 00:01:37,110 Um, so, um, so you see the title of my talk, but before I go to the nitty gritty details and try to explain what the title means, 18 00:01:37,620 --> 00:01:43,110 I would like to tell you or some of you remind you of another very interesting prospect. 19 00:01:43,890 --> 00:01:52,680 In the next few years, we actually will be able to observe, directly observed gravitational wave radiation for the first time. 20 00:01:53,370 --> 00:02:06,120 And actually we expect this to happen from two experiments. One is light go, which is a light in the foot ometer and the other is and works. 21 00:02:06,120 --> 00:02:11,880 It looks for gravitational wave radiation of frequencies between ten hertz and a thousand hertz. 22 00:02:12,600 --> 00:02:20,310 And the other the other is actually a astrophysical experiment which looks at the timing of pulsars. 23 00:02:20,670 --> 00:02:26,190 And both of them are and looks at very low frequency gravitational wave radiation 24 00:02:26,430 --> 00:02:30,120 frequencies that have periods of gravitational waves that are almost a year. 25 00:02:31,110 --> 00:02:36,749 And both of them are in the kind of race against the clock with each other to 26 00:02:36,750 --> 00:02:39,780 see which one is going to be the first experiment to see gravitational waves. 27 00:02:40,980 --> 00:02:46,920 And of course, gravitational waves are very important because they're the missing piece of the general theory of relativity. 28 00:02:47,610 --> 00:02:52,680 They are the ripples of spacetime that are created. If you have two very massive objects going around each other. 29 00:02:53,310 --> 00:03:00,299 And in astrophysics, these are stars, black holes, super stellar mass black holes. 30 00:03:00,300 --> 00:03:07,920 SuperMassive black holes. Um, they, they are spin to particles, so they are quadrupole radiation. 31 00:03:07,920 --> 00:03:14,340 So you're seeing the little video, how the vehicle that causes spacetime to oscillate in these two different shapes. 32 00:03:14,340 --> 00:03:22,980 This is a cross, an X plus, a cross polarisation and actually we already know that they're there. 33 00:03:23,910 --> 00:03:30,120 So in the figure that you see to the left, this is the eye. 34 00:03:30,420 --> 00:03:40,640 They they have already observe the increase in the period of a binary system to two pulsars going around each other as they fall towards it, 35 00:03:40,650 --> 00:03:48,940 either because they lose energy due to gravitational wave radiation. The red dots, as you see, we have observed that now in several binary systems. 36 00:03:48,940 --> 00:03:54,480 This, the first one that they've observed is this PSR B 1913 plus 56. 37 00:03:54,960 --> 00:04:00,090 They started driving it in the 1950s then before going for 30 years. 38 00:04:00,450 --> 00:04:05,460 The red dots are the measurement of the rotational period of the two objects around each other. 39 00:04:05,970 --> 00:04:10,890 And the blue line is the real prediction, and you see how well they agree with each other. 40 00:04:10,890 --> 00:04:19,540 So we know they have to be there. So again, so there is space time. 41 00:04:19,540 --> 00:04:28,509 So if you take the way you detect them is you take if you had to 2 to 2 masses to the masses, the distance, 42 00:04:28,510 --> 00:04:33,490 if you have a gravitational wave passing through them, the distance between the two masses will change. 43 00:04:34,600 --> 00:04:43,870 And in light go the light interferometer. You measure the change in the distance by using lasers and for the pulsar timing array, 44 00:04:44,500 --> 00:04:49,120 you use actually some of the best clocks that we have in the universe. 45 00:04:49,630 --> 00:04:57,220 Pulsars. They are frequency stability competes the ones with atomic clocks that can be better than one part in ten to the 15. 46 00:04:57,970 --> 00:05:02,920 And we look at the difference in the arrival times, the variation, 47 00:05:02,920 --> 00:05:09,850 the arrival time of the pulses from distance pulses within the local or local neighbourhood of the of the universe. 48 00:05:11,650 --> 00:05:22,000 And besides the fact that we will complete the theory of general relativity, we will also have new eyes to the universe we will start seeing. 49 00:05:22,120 --> 00:05:26,380 So given that they look at these two experiments, like going to look at different frequencies, 50 00:05:26,770 --> 00:05:32,890 we will see different properties of astrophysical objects in the universe like for example, 51 00:05:33,010 --> 00:05:43,510 is very sensitive to stellar mass objects that have roughly the mass of our sun coalescing and falling towards each other. 52 00:05:43,960 --> 00:05:50,350 While the PDA, the pulsar timing array, is more sensitive to the in spite of supermassive black holes, 53 00:05:50,350 --> 00:05:53,500 the holes the black holes that that in the centre of galaxies. 54 00:05:54,250 --> 00:06:01,090 And the great thing about this is that hopefully in five years or ten years, 55 00:06:01,390 --> 00:06:07,810 we will have a similar picture of the universe of our galaxy that we have in the optical. 56 00:06:07,810 --> 00:06:17,800 So this is a picture of of how the middle way looks at different frequency bands starting from the from radio waves all the way down to gamma rays. 57 00:06:18,790 --> 00:06:22,060 And we have different information come from that. So it's very exciting. 58 00:06:23,720 --> 00:06:26,970 Uh uh, so. 59 00:06:27,050 --> 00:06:36,650 And of course, we know there is a lot to learn besides learning many things about, um, a, 60 00:06:36,890 --> 00:06:46,250 about astrophysical properties and properties of black holes, neutron stars and the dynamics in our galaxy, in our galaxies, in the universe. 61 00:06:46,550 --> 00:06:51,590 We'll also learn new things about beyond the standard model of physics. 62 00:06:52,430 --> 00:07:06,500 So this this axis here summarises what we already know about in terms of length scales, what we already know about our world. 63 00:07:06,950 --> 00:07:09,350 So this big scale that we know is the Hubble scale. 64 00:07:09,860 --> 00:07:15,650 It's ten to the it's the size of our universe, ten to the 26 metres, the smaller scale that we know of. 65 00:07:15,950 --> 00:07:19,190 But there should be new physics is the Planck skill set by gravity. 66 00:07:19,520 --> 00:07:26,630 And these are six orders of magnitude apart, somewhere in the middle of this axis. 67 00:07:27,770 --> 00:07:39,950 Somehow, by coincidence, maybe we don't know that the dark energy, energy scale suits and which actually the dark energy, 65% of our universe. 68 00:07:40,610 --> 00:07:49,120 And we also have probably by coincidence also the neutrino mass goes up around there that on terms of minus three, 69 00:07:50,450 --> 00:07:56,030 if you go higher in energy, you start seeing that the standard model particles that we know of, 70 00:07:56,600 --> 00:08:01,280 the three families of leptons and quarks, along with the fundamental interactions, 71 00:08:01,700 --> 00:08:09,350 occupy some five orders of magnitude, starting from 500 k v for the air for the electron. 72 00:08:09,950 --> 00:08:13,190 And the LHC is pushing us toward higher energies. 73 00:08:13,880 --> 00:08:23,120 Now, if you sum up, if you in a large scale how much what we have observed this, you see that it only covers 80% of this energy scale. 74 00:08:24,100 --> 00:08:26,260 So there's a lot of things to learn and to explore. 75 00:08:27,670 --> 00:08:35,590 And as I've already said, there are already things to learn in the standard model because we have not observed gravitational radiation. 76 00:08:36,190 --> 00:08:39,580 We have not observed another thing that we know is there in the standard model, 77 00:08:39,850 --> 00:08:45,249 the cosmic neutrino background, which will have which will carry information about physics. 78 00:08:45,250 --> 00:08:49,420 That happened one second when the universe was one second. 79 00:08:50,950 --> 00:08:57,610 Of course, this is great, but it only accounts 5% for the known of the unknown energy budget of the universe. 80 00:08:58,090 --> 00:09:06,649 The rest, 95% has to be covered by what we know seems to be dark matter, which is 25%. 81 00:09:06,650 --> 00:09:16,450 Then the rest has to be covered by dark energy. And in string theory, one of the conditions to try to explain all of these string theory. 82 00:09:16,810 --> 00:09:26,750 You also have a few particles that come with our efforts to explain these dynamics, like axioms that photons, that sectors delight. 83 00:09:26,800 --> 00:09:30,910 On July, you may have heard all this. All this work has been thrown around. 84 00:09:31,720 --> 00:09:41,680 And this is something else that motivates expanding our search in this huge energy range that we know is there. 85 00:09:42,320 --> 00:09:47,000 So so this is so far putting everything in perspective. 86 00:09:48,340 --> 00:09:51,910 But for the rest of the talk, I will focus on one particle alone. 87 00:09:53,040 --> 00:09:57,989 And that is what particle physics a physicist knows that you should. 88 00:09:57,990 --> 00:10:04,590 The axiom capacity stands for quantum thermodynamics. 89 00:10:05,370 --> 00:10:08,579 It is the force. It's the strong interactions. 90 00:10:08,580 --> 00:10:17,880 It's the force that holds the nuclei together. It's derived from the world, from the Greek word Kurama, which is the Greek word for cholera. 91 00:10:18,810 --> 00:10:22,020 This is what we call the charge of the strong interactions. 92 00:10:22,200 --> 00:10:26,010 And this is what the charged quarks kind of its strong charge. 93 00:10:27,510 --> 00:10:35,970 Turns out that even in the standard model, strong interactions can introduce large violation of the charge. 94 00:10:36,180 --> 00:10:47,220 Part of the symmetry a charge a charge conjugation is the symmetry that takes that the changes positive to negative charges and vice versa. 95 00:10:47,850 --> 00:10:53,040 But these are symmetry that the symmetry. Symmetry. It takes it takes you from X to minus x. 96 00:10:54,530 --> 00:11:03,710 So the standard model turns out by allowed by all symmetries that we know in the Lagrangian, you can write down it. 97 00:11:03,860 --> 00:11:09,469 What looks like a base is the DOT product between the electric feel of the strong interactions, times, 98 00:11:09,470 --> 00:11:19,670 the magnetic field of the strong interactions and the way the the magnetic field is captured while the electric field, the CP. 99 00:11:19,670 --> 00:11:24,680 Even so, this term is something that mixes Scipio and CP even quantities, 100 00:11:24,680 --> 00:11:31,190 so it could be violating its effects of parameter rise by the Greek letter seta. 101 00:11:32,600 --> 00:11:38,750 It's called activity feedback. You see the angle and what this article does. 102 00:11:39,770 --> 00:11:44,000 It introduces an electric dipole moment for the neutral. 103 00:11:45,440 --> 00:11:48,349 So of course, the neutral by its name means neutral. 104 00:11:48,350 --> 00:11:56,960 But it doesn't mean that the charge over quarks, the concept that the charge of the quarks that constitute it is uniformly distributed over its size. 105 00:11:57,500 --> 00:12:03,920 So we're not totally expecting this parameter, given that what we know about the standard model, if we expected the parameter to be order one, 106 00:12:04,520 --> 00:12:11,510 meaning we expect to be the ETM, the electric dipole moment of the neutron to be of order, the charge times the size of the neutron. 107 00:12:12,320 --> 00:12:15,770 But we've looked for it for many, many years. 108 00:12:15,770 --> 00:12:22,250 Even back in the seventies they were looking for it and we found that we found nothing. 109 00:12:22,880 --> 00:12:28,580 All we've done so far is try to constrain this parameter to be less than ten to the minus ten. 110 00:12:30,000 --> 00:12:36,630 Even back in the in the seventies, this parameter was was constrain to be less than ten to the minus eight. 111 00:12:37,110 --> 00:12:42,360 So people wondered how do we solve the problem, a parameter that naturally we want to be put to one. 112 00:12:42,960 --> 00:12:46,350 We find it to be tiny and several. This was back to below one. 113 00:12:46,990 --> 00:12:57,030 So beton quy, along with the help of Weinberg and Franklin, checks Steve Weinberg and Frank Wiltshire. 114 00:12:57,300 --> 00:13:04,740 I said, Look, let's make this accidental dynamic fulfilled. And we called it Frank, called it reaction out of a detergent brand. 115 00:13:05,190 --> 00:13:09,000 He didn't have a good reason. We couldn't find a better name for it. 116 00:13:09,690 --> 00:13:20,900 And this action of it's the dynamic of food, its cosmic evolution dynamically relaxes this parameter to zero this off. 117 00:13:21,270 --> 00:13:25,770 So we know. So these properties of the action of this particle are well known. 118 00:13:26,280 --> 00:13:32,640 We can calculate them very well. We can calculate the mass and get from strong interaction corrections, 119 00:13:33,060 --> 00:13:40,630 from corrections from UCD and its parameters and its properties can be characterised by only one parameter. 120 00:13:40,650 --> 00:13:50,400 What you may hear me say during the talk axiom decay constant, and this is one continuous parameters that varies across the energies. 121 00:13:50,790 --> 00:13:56,790 And for a certain choice of this part, this part, for certain charge of this part of this particle is very, very light. 122 00:13:57,550 --> 00:14:01,510 Its constant wavelength is three kilometres. 123 00:14:02,580 --> 00:14:09,420 So if you compare it to what it is for the if you take the size of the proton, for example, it's one centimetre. 124 00:14:10,350 --> 00:14:16,470 So compared to the size of the proton, this is ten to the 18 times larger. 125 00:14:17,010 --> 00:14:22,739 So it's a very big particle, much bigger than the size of this, almost the size of Oxford. 126 00:14:22,740 --> 00:14:34,260 This is this downtown Oxford. So if you look at the particle data group and you look for actions and you see when when they summarise its properties, 127 00:14:34,470 --> 00:14:37,590 you will see a figure like this one axis, 128 00:14:37,590 --> 00:14:49,200 the action f, the action decay constant which characterises its interaction, strength and the measured in units of electron volts. 129 00:14:49,610 --> 00:14:53,570 And behind this parameter goes in giga electron volts. 130 00:14:53,580 --> 00:14:57,600 The bigger it gets, the more weakly the interaction of the action becomes. 131 00:14:58,950 --> 00:15:05,400 At the same time, this parameter, uniquely, as I said before, uniquely determines the mass or the quantum wavelength of the particle. 132 00:15:06,590 --> 00:15:13,100 Which can be as small as tens of microns or as large as thousands of kilometres. 133 00:15:14,090 --> 00:15:20,870 And for the rest of the dog, I will only talk about the oxygen mask and the Compton wavelength. 134 00:15:21,320 --> 00:15:31,040 So given that this idea is 30 years old, people have again have studied this particle and they know that it is also an 135 00:15:31,040 --> 00:15:34,670 excellent dark matter candidate for a certain part of its parameter space. 136 00:15:36,150 --> 00:15:42,660 Um, we've, we've looked for it, trying to find it in stages, but they didn't find it. 137 00:15:43,230 --> 00:15:53,640 And by looking at constraints come from a stark ruling, we find that its Compton wavelength has to be given roughly 30 microns. 138 00:15:55,380 --> 00:16:07,220 We've designed experiments to look for it. You may have heard cast people, as I saw, even at 100 people have looked for axioms. 139 00:16:07,560 --> 00:16:15,270 The first experiment to really probe the action parameter space outside too of what it is already constrained by. 140 00:16:15,270 --> 00:16:18,630 Astrophysics is an experiment at Washington University, 141 00:16:18,900 --> 00:16:28,080 at the University of Washington in Seattle called the Atom X and will probe this factor of roughly 100th in the oxygen parameter space. 142 00:16:28,890 --> 00:16:40,170 So. What I'll be talking today is about the process that probes the action in a part of its parameter space, 143 00:16:40,170 --> 00:16:45,000 where there's no current experiment that looks for it looking for it there. 144 00:16:45,900 --> 00:16:53,400 What I'm going to be talking about the actual wavelengths between 300 metres and 300 kilometres and the process that's 145 00:16:53,400 --> 00:17:01,290 involved in looking for this is super irradiance and in particular super radiance for astrophysical black holes. 146 00:17:05,410 --> 00:17:11,530 And the reason black holes are relevant is because of their size. 147 00:17:12,550 --> 00:17:17,980 So if you look at the size of astrophysical black holes, in particular black holes that come from the collapse of stars, 148 00:17:18,610 --> 00:17:23,470 you see that the size is roughly 15 kilometres for a certain solar mass. 149 00:17:24,280 --> 00:17:30,160 So that black hole, there are billions of them in the galaxy. 150 00:17:32,140 --> 00:17:34,960 Somewhere between 100 million and a billion in the galaxy alone. 151 00:17:36,020 --> 00:17:44,690 And they match the size matches the gives you the action for a certain part of its parameter space effects to measure the muscle. 152 00:17:44,720 --> 00:17:52,640 If if you measure the mass in the vs between ten to the -1310 to March 11, if we similarly couldn't imagine using supermassive black holes. 153 00:17:52,970 --> 00:17:56,720 Now they look for even lighter particles with much bigger wavelengths. 154 00:17:57,230 --> 00:18:04,160 Who's. Who's? Now we're talking about Compton, wavelengths of 24 seven kilometres approaching. 155 00:18:05,420 --> 00:18:13,010 If this is actually this one is close to the way to earth. 156 00:18:13,010 --> 00:18:20,919 Some distance. So now I'm going to tell you what black holes. 157 00:18:20,920 --> 00:18:27,730 But I didn't actually is and how how black holes can be turned into particle detectors. 158 00:18:28,470 --> 00:18:42,250 And so this was super ideas that I've been throwing around is has been known to people doing general relativity since the mid sixties. 159 00:18:43,940 --> 00:18:50,630 It's also known as the Penrose process, and it's a process that extracts energy and angular momentum from the black hole. 160 00:18:51,440 --> 00:18:54,740 So if now I'm looking for that, let's say you have a spinning black hole. 161 00:18:55,430 --> 00:19:00,499 And if you look at it from the top there, you have the rotating black hole in the middle with the horizon. 162 00:19:00,500 --> 00:19:05,380 And there's a region around it called the region. This is a very special region. 163 00:19:05,390 --> 00:19:09,090 What even like has to rotate? So if you take now. 164 00:19:09,510 --> 00:19:13,620 So what is the operator so prepared? And electromagnetic pulse. 165 00:19:14,910 --> 00:19:20,760 And you prepare an electromagnetic pulse in such a way that it takes the trajectory that takes it to their origin, 166 00:19:20,760 --> 00:19:30,260 but of course, not to the horizon of the black hole. And you see that it comes out with higher amplitude than what it came in. 167 00:19:31,900 --> 00:19:43,190 So in this process, the response has managed to increase its energy by extracting some of the mass energy. 168 00:19:43,610 --> 00:19:53,190 That means energy of the black hole and its angular momentum. A blessing to Gorski had the following amusing idea. 169 00:19:53,210 --> 00:19:58,840 They said, okay, let's repeat the same experiment and we take now. 170 00:19:58,930 --> 00:20:03,580 But at the same time now we take a perfectly spectacle mirror to put it around the black hole. 171 00:20:04,560 --> 00:20:11,160 In that case, what will happen is the electromagnetic pulse will start scattering. 172 00:20:14,950 --> 00:20:19,220 Oh, yeah. So we'll start gathering back and forth from here, 173 00:20:19,280 --> 00:20:29,070 go back to the mirror and eventually something that will start growing exponentially and the media will explode due to the huge radiation pressure. 174 00:20:29,870 --> 00:20:42,919 This is what they call super irradiance instability. And, um, and of course, I mean, you can imagine, okay, how do we realise this in a lab? 175 00:20:42,920 --> 00:20:49,520 I mean, we cannot make this perfectly circle metre, but it turns out what's to care about. 176 00:20:49,520 --> 00:20:55,430 Super identical of course, is having a bowser. And in particular if you have a massive boson, 177 00:20:56,270 --> 00:21:01,520 its mass will act like a mirror because now the massive bosom can create a bound state 178 00:21:01,520 --> 00:21:06,200 with a black hole that causes it to sit in the vicinity of black hole and leak. 179 00:21:06,200 --> 00:21:12,260 So all its wave function begins slowly through the in the ergo region, extracting the energy and angular momentum from the black hole. 180 00:21:12,830 --> 00:21:20,630 So those are the process is most efficient when the particle quantum wavelength is comparable to the black hole size. 181 00:21:23,680 --> 00:21:33,910 So now what you would expect to happen if you have a Nazi on or any bozo and a black hole that fits all five parameters much the right way. 182 00:21:34,210 --> 00:21:41,470 What you will see is the black hole start to spinning down and then you get this cloud of particles rotating around the black hole. 183 00:21:42,100 --> 00:21:45,610 Eventually the black hole, you spin down enough and the cloud will stop growing. 184 00:21:46,330 --> 00:21:51,120 This is. Oh, so this is what will happen. 185 00:21:51,130 --> 00:21:54,190 This is how you expect the accident from the existence of this cloud. 186 00:21:55,090 --> 00:21:59,800 So how does this cloud look like? Well, you see the very close to the black hole. 187 00:22:00,100 --> 00:22:06,870 You know what the potential is like. It's a mass because in one overarching Newtonian potential, it's not very special. 188 00:22:06,880 --> 00:22:13,060 So when you try to solve what the bound states looks like, they look like hydrogen wave functions. 189 00:22:13,720 --> 00:22:18,430 So what you have is a gravitational atom in the sky. So the fine. 190 00:22:18,700 --> 00:22:24,490 So again, you can define now you can describe its properties of the state very well. 191 00:22:24,970 --> 00:22:32,650 But just you have the fine structure constant, which determines the strength of the interaction between the black hole mass and the oxygen. 192 00:22:32,860 --> 00:22:36,639 So it's the product of Newton's constant times, the black hole masters, 193 00:22:36,640 --> 00:22:42,400 the action mass and the properties of each state can be described by three quantum numbers, 194 00:22:42,850 --> 00:22:48,940 the principal quantum number, and which of them is the energy of the energy level, the orbital quantum number? 195 00:22:49,540 --> 00:22:56,380 L Which is of course, the angular momentum and the magnetic quantum number and which is the projection of the angular momentum in the Z direction. 196 00:22:57,820 --> 00:23:05,820 And if you calculate what the energy binding energy is, of course, you find similar things to what you find for there for the hydrogen atoms, 197 00:23:05,830 --> 00:23:11,200 just alpha squared times the mass of the particle instead of the mass of the electron over ten squared. 198 00:23:11,260 --> 00:23:17,560 But n is the principal quantum number. So of course, though, there's one main difference with a hydrogen atom, 199 00:23:18,220 --> 00:23:23,500 instead of fermions occupying these energy levels, you have actions and actions at bottom. 200 00:23:24,100 --> 00:23:29,650 So instead of maximally two particles at each level, you can have ten of the 75. 201 00:23:31,390 --> 00:23:38,910 So you have this entire so this is a very classical. So it's like having a Bose-Einstein condensate rotating around the black hole. 202 00:23:40,040 --> 00:23:45,649 Um, so, uh, which levels can cause this? 203 00:23:45,650 --> 00:23:56,960 The question is, um, there's out so I'll go through slowly here there is out a super radiance is a kinematic condition. 204 00:23:58,520 --> 00:24:07,159 So it happens not the level comes, but at the actually most levels if you have, if you put any action in in one of those levels, 205 00:24:07,160 --> 00:24:12,110 what we will see most of the time is that the action falls back into the black hole. 206 00:24:12,590 --> 00:24:16,040 It doesn't want to do anything, just be absorbed by the horizon of the black hole. 207 00:24:16,790 --> 00:24:23,300 The special ones are the ones for which the total energy of the action in this bound state, 208 00:24:23,540 --> 00:24:35,390 which is the action mass plus the binding energy, has to be less than the product of the magnetic and quantum number of a state times. 209 00:24:35,870 --> 00:24:40,250 This quantity Omega plus, which has a weird formula, depends of the spin of the black hole. 210 00:24:40,490 --> 00:24:45,200 But you can think about it as the angular rotational velocity of the black hole. 211 00:24:46,220 --> 00:24:51,370 Um, so, uh. So this is, uh. 212 00:24:51,500 --> 00:24:54,860 This sounds a bit magical. The best way. 213 00:24:55,160 --> 00:25:06,290 The best understanding I found to explain what this cinematic condition is, is in some beautiful papers by their dovish and Bacons type. 214 00:25:06,890 --> 00:25:10,730 So sporadic. So they they. 215 00:25:11,030 --> 00:25:13,070 These are papers that were written in the seventies. 216 00:25:13,520 --> 00:25:20,400 But that's really the first version of Super Radiance that was ever put down in literature is called inertial motions, 217 00:25:20,430 --> 00:25:26,360 parabens or else cherenkov radiation. So what happens in Chekhov radiation. 218 00:25:26,360 --> 00:25:30,980 And this is probably something that you've all seen pictures, the blue light coming out of reactors. 219 00:25:31,940 --> 00:25:35,930 So in that case, you have a very energetic, very, 220 00:25:36,260 --> 00:25:44,090 very fast moving particle that goes through a medium with a speed that's higher than the speed of light in the medium. 221 00:25:45,620 --> 00:25:47,360 When this condition is satisfied, 222 00:25:47,390 --> 00:25:54,260 the particle starts emitting spontaneously and we think ahead of the dish and turns out it's picked up a UAV for the electron. 223 00:25:54,270 --> 00:25:59,240 So that's why you get the blue light. So this is for linear motion. 224 00:25:59,810 --> 00:26:03,680 You get actually an analogous effect when you have rotation. 225 00:26:04,640 --> 00:26:08,960 So now what you have is a cylinder less like a cylinder. 226 00:26:09,800 --> 00:26:14,660 It doesn't have to be. And you can think of a black hole, take a picture of a black hole as a cylinder. 227 00:26:15,110 --> 00:26:20,030 And now you, Scott, think it's got that from the cylinder and the electromagnetic wave, 228 00:26:20,750 --> 00:26:26,120 which because you're talking about rotation now you you call the compose in you have E to the 229 00:26:26,120 --> 00:26:34,700 Iomega T minus from five because you're decomposing as a muscle in a num car in momentum, 230 00:26:34,880 --> 00:26:45,140 in angular momentum, I get functions. And now the requirement is that the object that does the rotation moves faster than 231 00:26:45,140 --> 00:26:52,010 the it has angular velocity that is faster than the angular phase velocity of light. 232 00:26:53,570 --> 00:26:57,460 Um, uh, in particular. Actually, there is another example. 233 00:26:57,620 --> 00:27:06,160 If you have the, you can even imagine this for a particle. If you have a cylinder and you want to scatter a particle tangentially from the cylinder 234 00:27:06,550 --> 00:27:11,680 in order for the particle to come out with a higher velocity than what it came in, 235 00:27:12,040 --> 00:27:19,690 it has to come out, come in tangential it with slightly less linear velocity than, than the rotational velocity of the cylinder. 236 00:27:21,340 --> 00:27:28,180 So, uh, uh, so I'm trying to spit out this is not very special. 237 00:27:28,780 --> 00:27:35,259 It has nothing to do with strong gravity. You can imagine you can design systems in the lab with just electromagnetic interactions 238 00:27:35,260 --> 00:27:39,610 with separate things can occur and people have indeed tried to do experiments on this. 239 00:27:40,780 --> 00:27:47,500 Um, the other important parameter is the rate of growth for radians. 240 00:27:49,040 --> 00:27:55,600 So people have calculated this, uh, it's basically, it has to do with wave function overlap. 241 00:27:55,630 --> 00:28:01,420 How much the wave function of the action within the ball state overlaps with the ergo region. 242 00:28:01,960 --> 00:28:12,330 And we find that the fastest we can be is ten to the seven times the full time to the black hole the size of the black hole in. 243 00:28:12,340 --> 00:28:19,540 Uh, uh, so if you convert this to seconds for a one Solomon's Black Hole, this is 100 seconds. 244 00:28:21,850 --> 00:28:27,670 And if you compare it to the two, for example, if you if you want to know what does it mean for astrophysics? 245 00:28:27,940 --> 00:28:32,889 The dynamical evolution timescale for black holes, which is called the electron accretion rate, 246 00:28:32,890 --> 00:28:38,080 is how fast black holes accrete each stuff and grow is ten to the eight years. 247 00:28:39,170 --> 00:28:44,120 So four astrophysical black holes. So you have 400 seconds compared to 10 to 8 years. 248 00:28:44,720 --> 00:28:54,830 So for astrophysical black holes, turns out even though this effect naively seems small, it has a lot of time to grow and affect their properties. 249 00:28:54,830 --> 00:28:58,790 The properties of astrophysical, black hot. And again, 250 00:28:59,060 --> 00:29:11,150 we have the like a coincidence that for stellar mass black holes this size can match the Compton wavelength of the gas should the oxygen for a decade. 251 00:29:11,150 --> 00:29:14,300 Constance that that around the Planck scale. 252 00:29:16,620 --> 00:29:21,900 So this is this is a slide that summarises what I've told you so far. 253 00:29:22,200 --> 00:29:25,380 So Supernatants actually has nothing to do with gravity. 254 00:29:25,830 --> 00:29:31,500 It's just a purely kinematic effect. You can design systems in the event in the lab where this happens. 255 00:29:33,030 --> 00:29:38,580 There's out. You need to move very fast because it's still a super luminosity condition of some sort. 256 00:29:38,970 --> 00:29:43,980 So black holes are great because they spin very fast and they have very strong gravity. 257 00:29:45,120 --> 00:29:48,929 And the other thing that black holes do, because exactly. They have very strong gravity. 258 00:29:48,930 --> 00:29:57,059 They're very good vacuum cleaners. So they can clean the environment well enough so that any gravitational potential 259 00:29:57,060 --> 00:30:00,630 perturbation around the black hole does not perturb the potential of the state. 260 00:30:00,900 --> 00:30:04,140 It does not cause it to fall back to black hole. 261 00:30:06,840 --> 00:30:15,899 So to see how this effect, how this effect evolves for us, the physical system for it, 262 00:30:15,900 --> 00:30:21,660 for a realistic astrophysical black hole, what you need to know is, of course, how fast does the instability grow? 263 00:30:22,560 --> 00:30:29,640 How does it how fast is the sequential growth happens? What is the dynamical scale of black, of the evolution of the black hole, 264 00:30:30,120 --> 00:30:35,190 which I've already told you is said by the accretion rate, which is roughly ten to the eight years. 265 00:30:40,140 --> 00:30:49,560 I won't go into this detail, but there's something interesting that can happen when you have oxygen safe interactions, 266 00:30:49,950 --> 00:30:57,750 when you have oxygen safe interactions. They can affect the evolution of the. 267 00:30:58,740 --> 00:31:05,250 Of of the effect. So when the energy due to self interactions in this huge cloud of ten to the 75 268 00:31:05,260 --> 00:31:11,130 actions becomes comparable to the binding energy of the state of the black hole. 269 00:31:11,160 --> 00:31:12,210 The cloud collapses. 270 00:31:13,270 --> 00:31:24,340 And you actually get the very, very, very spectacular effect that they've actually observed for real Bose-Einstein condensates in the lab. 271 00:31:24,610 --> 00:31:35,830 And it's called the Bossa Nova Effect, taken from, uh, uh, the, um, the similar name for the astrophysical instability of stars. 272 00:31:36,650 --> 00:31:40,510 Um, now signals, what do signals how would we know that this actually happened? 273 00:31:41,950 --> 00:31:51,580 So given that I've been talking about atom and hydrogen wave functions, the first thing you would expect is transitions. 274 00:31:52,450 --> 00:31:59,470 You have this gravitation of atoms, so you expect the transitions of actions between different levels of this atom 275 00:31:59,830 --> 00:32:05,950 and simultaneous admission of gravitational wave radiation because of reactions. 276 00:32:05,980 --> 00:32:11,890 These are bosons that occupy exactly the same state. So you get a gravitational wave laser. 277 00:32:12,730 --> 00:32:20,100 So what you get out of this process is a very monochromatic signal whose strength is enhanced by the product of the occupation. 278 00:32:20,110 --> 00:32:21,160 Number of these two sets. 279 00:32:23,130 --> 00:32:36,630 Another similarity monochromatic process that is not you may not be very familiar with is action in relation to one graviton. 280 00:32:37,260 --> 00:32:42,510 And this happens because gravitons are particles. If they are, they are only particles. 281 00:32:42,840 --> 00:32:46,140 So in fact, two axioms can relate to grab atoms. 282 00:32:46,920 --> 00:32:54,180 But what happens now? Because you have the black hole, one graviton gets falls back into the black hole and you only get one coming out. 283 00:32:54,900 --> 00:33:00,210 So this actually has been observed. A similar effect has been observed for the atom, the positron. 284 00:33:00,720 --> 00:33:06,510 So you can take positrons and throw them towards electrons with are bound to atoms. 285 00:33:07,110 --> 00:33:14,850 And what happens in the case of spin out of the positron annihilate in two photons, you select them positrons and you get into only one photon. 286 00:33:15,540 --> 00:33:19,890 Because now the photons that were supposed to come out get absorbed by the nucleus, 287 00:33:20,520 --> 00:33:23,730 who got all the recoil to preserve energy and momentum in the process. 288 00:33:25,290 --> 00:33:33,730 I'm. So let's let's follow now the history of spreads, huh? 289 00:33:34,150 --> 00:33:40,180 So now let's start with the stellar mass black hole. This is a plot that shows in the in the Y axis. 290 00:33:40,180 --> 00:33:43,329 You see, the parameter is that the parameter rises. 291 00:33:43,330 --> 00:33:47,620 The spin of the black hole zero is a non spinning black hole spots a black hole. 292 00:33:47,980 --> 00:33:53,200 One is extreme a black hole. It's the fastest it can be. Possibly spin, basically rotational velocity of one. 293 00:33:55,450 --> 00:34:01,570 And on the on the x axis you can see the black hole mass masses in solar masses. 294 00:34:02,680 --> 00:34:12,100 The black dot that you see there is a solar mass is a stellar mass black hole of over because of mass six solar masses. 295 00:34:12,760 --> 00:34:18,940 Um, and we, we started with theta when it was first created after the supernova collapse, 296 00:34:19,600 --> 00:34:25,330 you would get a black hole that has this mass and it's been that close to 3.95. 297 00:34:27,010 --> 00:34:32,350 What is shaded now in blue is the different super advanced level. 298 00:34:32,950 --> 00:34:36,130 And for a given action of mass of tens of -11, 299 00:34:36,340 --> 00:34:43,050 which is a Compton wavelength of roughly three kilometres and this is this this black dot sits in the region. 300 00:34:43,060 --> 00:34:47,020 What it would be affected by to produce. So what happens? 301 00:34:47,660 --> 00:34:54,610 Uh, since it is affected by Irradiance and in this case, the one that's relevant for separate things is the equal to level. 302 00:34:56,830 --> 00:35:03,790 The equal status to level starts growing. And for these parameters, it takes roughly two years to grow. 303 00:35:04,750 --> 00:35:14,560 At that point. At some point, the the the black hole loses so much pain that the level no longer satisfies the sporadic condition. 304 00:35:14,860 --> 00:35:21,640 And you stop growing and you get stuck along this line that because it's a relation between what has been called the trajectory. 305 00:35:23,750 --> 00:35:27,530 Then there is out for reasons that I don't have time to explain. 306 00:35:27,890 --> 00:35:34,880 The blood clot stays there for roughly ten to the six years for about a million years before the next level starts. 307 00:35:34,970 --> 00:35:43,010 It starts starts growing and then the next level starts growing and you fall down again in Spain. 308 00:35:45,200 --> 00:35:51,230 Oh. And this time we fix it for a longer time. They extend to the four years for this process to happen. 309 00:35:51,530 --> 00:35:55,050 At some point you stop growing, but there is no longer a focus. 310 00:35:55,100 --> 00:35:59,389 But I call because the rate for the next, for the timescale, 311 00:35:59,390 --> 00:36:04,930 for the next level to grow is bigger than the Eddington accretion rate or the age of the universe. 312 00:36:04,940 --> 00:36:07,640 So the black hole is no longer affected by sporadic. 313 00:36:09,080 --> 00:36:15,530 The reason, by the way, that you go vertically in the mass and this whole process, you lose a lot of speed, but not a lot of mass. 314 00:36:15,890 --> 00:36:19,010 The reason is that the cloud is much bigger than the black hole. 315 00:36:19,490 --> 00:36:25,970 So you have the ballerina effect. So you can carry a lot of angular momentum without having to carry too much mass. 316 00:36:26,690 --> 00:36:29,540 So that's why it moves vertically across this plot. 317 00:36:32,210 --> 00:36:41,330 The interesting thing is that actually what I've drawn here is that is a realistic situation because we can learn something from it. 318 00:36:42,320 --> 00:36:47,690 So if we had an action that has a quantum wavelength, for example, three kilometres here, 319 00:36:48,380 --> 00:36:55,520 it would have effective all of black holes, all of stellar mass black holes in the in the universe that were sitting in the blue. 320 00:36:56,480 --> 00:37:00,260 And you should have no black holes in the blue region. 321 00:37:00,260 --> 00:37:07,960 And all the black holes should be concentrated in the white region. And we've actually done measurements. 322 00:37:08,890 --> 00:37:14,080 People have actually started measuring and this has been going on for 15, almost 30 years now. 323 00:37:14,920 --> 00:37:21,130 People have measured in spins and masses of both stellar mass and supermassive black holes. 324 00:37:21,610 --> 00:37:25,360 And this is actual data. 325 00:37:27,040 --> 00:37:31,180 So this, again, a plot that shows the black hole spin is a function of black hole mass. 326 00:37:32,050 --> 00:37:38,200 And we've drawn here for a roughly one kilometre sized action. 327 00:37:38,530 --> 00:37:48,130 And you see that that action do you see that red point up there that actually this now this measurement excludes the action that's plotted here. 328 00:37:48,820 --> 00:37:54,580 So you can actually put constraints. And we've done that. 329 00:37:55,660 --> 00:37:57,580 And you can make plots that look like this. 330 00:37:57,880 --> 00:38:05,800 So on the horizontal axis you put, you can do it separately for stellar and supermassive and supermassive black holes. 331 00:38:06,280 --> 00:38:11,530 So on the top, right, you see what you learn from stellar mass black holes. 332 00:38:13,750 --> 00:38:17,320 One axis is the action mass or the action quantum wavelength. 333 00:38:17,560 --> 00:38:20,650 The other axis is the action solely for interaction. 334 00:38:21,430 --> 00:38:25,500 At some point as you go up into the Y axis, the action. 335 00:38:25,510 --> 00:38:30,520 So that actually becomes stronger and stronger. And at some point it inhibits the growth of. 336 00:38:30,820 --> 00:38:34,240 And so you don't get a fixed for a superior view. 337 00:38:35,650 --> 00:38:41,050 And this is for a similar for supermassive black holes. So this is actually the first ever constraint, 338 00:38:41,470 --> 00:38:46,480 what appears to be the first ever constraint for the use of the action that part of the of parameter space. 339 00:38:47,260 --> 00:38:51,730 And this has happened like 30 years after it was first proposed. So now let's go to. 340 00:38:52,180 --> 00:38:57,220 So, of course, these exclusions. This is not very interesting, but let's talk about signatures. 341 00:38:58,330 --> 00:39:01,870 Again, as I told you, this is a gravitational atom. 342 00:39:02,500 --> 00:39:11,290 And turns out for this gravitational atom, the you can have levels that have the same angular momentum kind of numbers, 343 00:39:11,680 --> 00:39:19,480 but different principal quantum numbers that can be occupied by large number of accidents at the same time. 344 00:39:20,530 --> 00:39:24,429 And you can have transitions of oxygen for stellar mass black holes. 345 00:39:24,430 --> 00:39:29,799 The transitions appear at frequency at anywhere from 15 to 150 hertz for the 346 00:39:29,800 --> 00:39:33,600 Q should the action which is the optimal frequency band for advanced legal. 347 00:39:35,050 --> 00:39:36,879 As I told you, the signal is enhanced. 348 00:39:36,880 --> 00:39:47,350 It's like a losing effects of the signal is enhanced by the by the occupation number, by the product number of the two levels. 349 00:39:49,270 --> 00:39:56,409 You bet. If this also determines the signal strength, this h you don't worry about this formula. 350 00:39:56,410 --> 00:40:02,620 I should have removed it. And the signal loss can last from anywhere from one here to 100 years. 351 00:40:03,850 --> 00:40:12,070 Um, so we took, um, so people have done feats of the distribution of the, they've, 352 00:40:12,250 --> 00:40:17,350 they've done feat by, by measurements of the distribution of black hole masses, 353 00:40:17,350 --> 00:40:26,650 black holes spins as well as the black hole distribution stellar mass black hole distribution in our galaxy. 354 00:40:27,370 --> 00:40:37,210 So we can take those distributions. I take into account the birth rate of black holes and estimate how many, given the sensitivity of advanced LEGO, 355 00:40:37,510 --> 00:40:46,030 how many black holes will advance like you'll be able to observe going through the sporadic process while the experiment is running. 356 00:40:46,990 --> 00:40:56,170 And we took as they do for when they calculate event rates for uh, for inspired us we took a pessimistic, 357 00:40:56,170 --> 00:41:02,530 realistic and optimistic assumptions and we get this plot from the bottom, right? 358 00:41:02,770 --> 00:41:07,570 So this is the number of expected events as a function of the actual mass. 359 00:41:08,970 --> 00:41:16,020 And what you see here, of course, given the loss, as you see, the first thing you see, astrophysical uncertainties are huge. 360 00:41:16,590 --> 00:41:24,120 You can get something that's event rates that go from depending on the action must have zero from 1 to 10 to the minus three. 361 00:41:26,040 --> 00:41:34,060 So this signal is a bit probably a bit tough to see in advance, like, oh, these are not very they couldn't be better. 362 00:41:34,590 --> 00:41:35,700 They could also be worse. 363 00:41:36,440 --> 00:41:47,100 So and what you cannot see actually in grey of this plot doesn't show very well what is already excluded by spin measurement. 364 00:41:48,450 --> 00:41:51,900 The most promising, though, signature for the. 365 00:41:54,170 --> 00:41:59,690 Four four for observing actions of advance legal is action in relations. 366 00:42:01,430 --> 00:42:08,060 So you think, as I told you, this is a process that takes two actions and produces one graviton. 367 00:42:08,630 --> 00:42:15,530 The frequency, the energy of the action of the graviton is twice the action muscles, the direct measurement of the action mass here. 368 00:42:16,160 --> 00:42:20,660 And the frequency appears at very high frequency for the gives you the actions for these parameters of the 369 00:42:20,660 --> 00:42:28,730 drums can be above kilohertz around the kilohertz again because this action sit exactly on the same state. 370 00:42:29,330 --> 00:42:35,809 This is a process that the hands by the occupation, by the number of above, by the number of actions the signal person has, 371 00:42:35,810 --> 00:42:41,450 but the number of actions quit in the cloud so you can get something reasonable. 372 00:42:41,450 --> 00:42:50,570 This signal actually, because this process turns out is much slower than transitions, the signal can last up to thousands of years. 373 00:42:51,770 --> 00:42:54,770 And this is good because. 374 00:42:55,910 --> 00:43:03,290 It makes our signal observable, more easily observable at the vast library. 375 00:43:04,040 --> 00:43:08,980 So again, we took the same assumptions for the distribution of black holes. 376 00:43:09,020 --> 00:43:12,930 PS Masses you cannot really see. 377 00:43:13,010 --> 00:43:16,540 Is it a pointer? That should be. Yeah. 378 00:43:16,560 --> 00:43:21,550 Here. Uh. Let's see here. 379 00:43:21,970 --> 00:43:30,030 Okay, so here is what is excluded. This grey band. Here is what they excluded currently by black hole spin measurements. 380 00:43:30,060 --> 00:43:36,540 This is the actual mass here. And now you see that the event rates have gone precipitously up. 381 00:43:37,500 --> 00:43:43,200 You can imagine the owners get thousands, more than thousands of events, if there is an axiom there. 382 00:43:43,830 --> 00:43:48,809 And if the right must care, this corresponds actually to actually the conference around the Planck scale, 383 00:43:48,810 --> 00:43:59,820 which is actually it's a well-motivated scale. And you see that advance, like what could be it could be turning on and see thousands of events. 384 00:44:00,210 --> 00:44:05,820 That means thousands of black holes have an oxygen cloud around them, producing monochromatic gravitational wave radiation. 385 00:44:07,950 --> 00:44:10,110 So, of course, though, as you can see, again, 386 00:44:11,100 --> 00:44:18,870 there is huge uncertainties that have to do with black hole distribution and black hole spin distributions in our galaxy. 387 00:44:19,830 --> 00:44:21,960 Nevertheless, this is extremely interesting. 388 00:44:23,950 --> 00:44:34,750 Uh, and so, uh, so and so I've, we've, we are in touch with like people and they seem to be very excited about it. 389 00:44:35,230 --> 00:44:39,010 Um, so this is a blog that summarises what I have told you. 390 00:44:39,400 --> 00:44:52,450 So black holes turns out. Ah, a have provided us with a natural detector of this of a large wavelength particles, black holes. 391 00:44:52,450 --> 00:45:04,179 But I think it's a process that has been known for a long time and it can be used for can turn black holes into particle detectors and probes, 392 00:45:04,180 --> 00:45:05,680 a very well-motivated particle, 393 00:45:05,680 --> 00:45:14,470 a particle that could be the dark matter of the universe in a part of its parameter space that is not probed by any run experiment. 394 00:45:14,830 --> 00:45:21,250 There are several. There is only one proposal that probes a similar part of the action parameter space, 395 00:45:22,030 --> 00:45:31,930 but that also assumes that the reactions that come out so black holes operatives does not care if the particle is any component of dark matter. 396 00:45:32,200 --> 00:45:37,150 It will happen if the particle has a gravitational copy and that's it. 397 00:45:38,300 --> 00:45:50,630 Um, so and I and as we estimate, it turns out that advanced light, which is about to turn on is about to start in a few years, 398 00:45:50,990 --> 00:45:56,510 will be sensitive in a part of the parameter space where there are currently no other constraints. 399 00:45:56,840 --> 00:46:05,990 And this will come just from astrophysics and because of irradiance, not because just in and because of that identity kinematic effect. 400 00:46:06,410 --> 00:46:15,709 And all you care about is your particle boson. Those are audience is a process that will be sensitive to any light particle that 401 00:46:15,710 --> 00:46:20,390 is a boson and has a constant wavelength larger than a thousand kilometres, 402 00:46:21,260 --> 00:46:23,420 naturally kilometres. So. Thank you.