1 00:00:10,450 --> 00:00:13,510 My photos actually on searches from black holes to the basement. 2 00:00:13,780 --> 00:00:19,030 As you'll see, the basement includes basements here in Oxford. And there are a lot of Oxford connections for the research I'm to tell you about. 3 00:00:19,510 --> 00:00:30,919 Yeah. So this topic is how to discover fundamental so not in the current condensed matter context that just told us about fundamental axioms. 4 00:00:30,920 --> 00:00:35,150 Axioms. Why should you own or actually own some string theory or axiom like particles? 5 00:00:36,380 --> 00:00:41,270 And there are a huge range of possibilities for searches, for axioms. 6 00:00:41,270 --> 00:00:43,430 This is actually an immensely growing field. 7 00:00:43,760 --> 00:00:49,669 In fact, over the last ten years there have been literally hundreds of new experiments and observations suggested. 8 00:00:49,670 --> 00:00:55,190 And so this is one of most exciting fields of experimental physics, experimental astrophysics and cosmology. 9 00:00:55,550 --> 00:01:01,520 So here is the axiom math I'm always going to call the actual mass you saw by here in TV. 10 00:01:01,520 --> 00:01:08,650 And this a very wide range of masses. And actually this is only a subset of all the possible mass is the axiom could have you say many of 11 00:01:08,660 --> 00:01:14,780 magnitude and every one of these things is a different experiment or observation or test you can do. 12 00:01:14,780 --> 00:01:21,770 So it's really quite incredible the range of things. And I'm going to tell you about two particular bits of this diagram and two particular things. 13 00:01:23,780 --> 00:01:26,800 So I want to tell you, just remind you just a little bit of actions. 14 00:01:26,810 --> 00:01:28,250 The things can be important for us. 15 00:01:28,370 --> 00:01:36,679 So as Joe explained to us, actually expected to often be very light with mass is much, much below the electron mass, let's say. 16 00:01:36,680 --> 00:01:43,220 And as you showed on this diagram for I was looking at a lot of axioms, what may be one of your ten to the minus ten TV or even lighter axioms. 17 00:01:43,940 --> 00:01:48,560 Right. And also expected and constrained to be very feebly interacting. 18 00:01:49,970 --> 00:01:53,090 So that's the two things. They're very light, they're very feebly interacting. 19 00:01:53,300 --> 00:01:57,410 They also have a whole variety of types of interactions with normal matter. 20 00:01:57,410 --> 00:02:00,440 And I'm going to discuss those types later on. 21 00:02:00,920 --> 00:02:09,230 Okay. Now the key see the axial has this formula for its mass which were like this scale fe 22 00:02:09,500 --> 00:02:14,899 sometimes called the axis on the constant or something like this to the axial mass. 23 00:02:14,900 --> 00:02:22,280 So there's a definite relation. So for instance, I took for you to be ten to the 17 gives a large scale that's close to the unification scale. 24 00:02:22,580 --> 00:02:25,880 Then the kicking axial mass will be this tiny number. 25 00:02:26,090 --> 00:02:30,860 And if and later on you'll see it's useful to express this in terms of distances. 26 00:02:30,860 --> 00:02:36,640 So the in terms of distances, this constant wavelength is three kilometres, three kilometres inversely, right? 27 00:02:36,650 --> 00:02:39,770 So the constant wavelength would be three kilometres. Right. 28 00:02:39,830 --> 00:02:41,090 And that's going to be interesting for us. 29 00:02:41,330 --> 00:02:47,390 And this formula was first really written down by Weinberg and we'll check in the very famous papers in the late seventies. 30 00:02:48,560 --> 00:02:55,490 So this scale, if I use large scale, also suppresses all interactions the action by one over five factors. 31 00:02:55,730 --> 00:03:02,300 So correspondingly because the scale is very large constrain to be very large for fundamental actions, this is a very feebly interacting particle. 32 00:03:03,110 --> 00:03:09,460 Okay, now this is the relation for the Q, see the XY on axial like particles of generalised. 33 00:03:09,560 --> 00:03:14,480 You see the action like curve very often in string theory share many features of the action, 34 00:03:14,480 --> 00:03:21,260 except they don't have this tight relationship between mass and this this scale, this strength of the couplings. 35 00:03:21,590 --> 00:03:24,620 Right. That's violated or broken. Right. 36 00:03:24,620 --> 00:03:30,680 So Axion, mass and Axion interaction, strength for this scale and our independent parameters. 37 00:03:31,490 --> 00:03:37,220 And that's the thing I want you to remember about. So back to the huge range of possibilities. 38 00:03:37,250 --> 00:03:42,440 They come in broad categories. We could do collider experiments with new particles and fact. 39 00:03:42,470 --> 00:03:46,490 How this is the original. Weinberg We'll check axioms look for in fact the original proposal. 40 00:03:46,490 --> 00:03:52,190 Weinberg would check what they thought the mass of the actual might be was rolled out very quickly by precision. 41 00:03:52,190 --> 00:03:57,980 Experiments are colliders. There's also either astro or cosmological observations. 42 00:03:58,280 --> 00:04:03,769 Well, we can either look for new particles, new forces, or it could be the dark matter, as you'll see. 43 00:04:03,770 --> 00:04:09,590 That's a very interesting possibility. We can also do lab experiments looking for new forces. 44 00:04:09,980 --> 00:04:15,410 Or again, it could be that this axial natural light particles of the dark matter and we see that's a very exciting possible the in fact, 45 00:04:15,410 --> 00:04:19,370 there's a whole range of other things here. All the categories even I'm not even go into. 46 00:04:20,620 --> 00:04:23,649 So I'm going to focus in this talk on two things. 47 00:04:23,650 --> 00:04:29,500 I'm going to focus on what is a very interesting astrophysics constraint on new particles. 48 00:04:29,620 --> 00:04:32,170 It doesn't have to be the dark matter. All right. 49 00:04:32,560 --> 00:04:37,570 And I'm also going to go in the second half of my talk lab experiment, searching for Axion dark matter. 50 00:04:37,570 --> 00:04:40,899 So I'm going to tell you two different things and those are particularly interesting. 51 00:04:40,900 --> 00:04:44,830 One, well, they are strong also connections with both of these things. 52 00:04:45,760 --> 00:04:53,829 That's nice. But also on this diagram, the astro thing involves black holes and you see this a very strong constraint. 53 00:04:53,830 --> 00:04:55,920 This goes down to even very, very tiny couplings. 54 00:04:55,920 --> 00:05:02,000 And actually, if this thing was to extend off further to the left in mass, it would go down way lighter ranges. 55 00:05:02,030 --> 00:05:05,620 So it's a very stringent and very good constraint over a lot of parameter space. 56 00:05:05,890 --> 00:05:10,480 And the other thing the lab experiments impacts on dark matter also are very sensitive. 57 00:05:10,480 --> 00:05:17,530 So you see most of these things are up here, but these are some of the things that go down towards this action of the action line. 58 00:05:17,530 --> 00:05:24,009 So this strong relationship between mass and coupling strength is this line here for the case of Axion outs can live anywhere in 59 00:05:24,010 --> 00:05:29,800 this diagram general out of 50 actually is here and these experiments are some of the few that get down to sufficient sensitivity. 60 00:05:29,950 --> 00:05:35,739 So I'm going to tell you about these two classes of things and the very interesting new physics and thoughts. 61 00:05:35,740 --> 00:05:40,870 What's going on here, both theoretical and experimental. So first, the astro constraints. 62 00:05:42,780 --> 00:05:48,690 So it is a very remarkable statement. I'm one of the people who came up with this. 63 00:05:48,720 --> 00:05:51,900 I'm with my friends on the West Coast in the States. 64 00:05:52,230 --> 00:05:57,540 Remarkably, astrophysical black holes provide a way to search for light actions, 65 00:05:57,960 --> 00:06:02,230 and this search only depends upon their absolutely mandated gravitational interactions. 66 00:06:02,300 --> 00:06:05,750 So this, in fact, doesn't use any of the weak couplings. Right. 67 00:06:05,760 --> 00:06:10,230 The only thing it cares about is the fact that you interact with gravity and everything interacts with gravity. 68 00:06:10,390 --> 00:06:15,420 We're going to use that. This is very powerful. In fact, you can be used to search for any light particles. 69 00:06:15,990 --> 00:06:22,709 With one caveat I'll tell you about. So we're going to use what we now know exists. 70 00:06:22,710 --> 00:06:30,420 And I'm doing this, which is black holes. I'm going to tell you about black hole, super radiance or an acciones or black holes as nature's detectors. 71 00:06:31,440 --> 00:06:36,679 Right. So we know now remarkably, of course, that as fiscal black holes exist, 72 00:06:36,680 --> 00:06:42,970 we see advanced like I have seen gravity wave signals from merging black holes. 73 00:06:42,980 --> 00:06:46,900 We have a whole family of mergers of different black holes, masses. 74 00:06:47,240 --> 00:06:52,370 We know actually that there are lots of different black holes and binary black holes existing in our universe. 75 00:06:52,610 --> 00:06:57,679 And we know that the short idea the size of these black holes varies from a few kilometres for 76 00:06:57,680 --> 00:07:04,370 solar mass black holes up to 10 to 10 kilometres for the biggest galactic centre black holes. 77 00:07:04,550 --> 00:07:09,980 So some of these things can be unbelievably huge this few kilometres. 78 00:07:10,430 --> 00:07:14,419 Remember I gave you this for three kilometres? What the quantum wavelength for the Axion might be. 79 00:07:14,420 --> 00:07:18,170 In certain case, that's going to be an important, quote unquote coincidence. 80 00:07:19,480 --> 00:07:23,080 All right. So moreover, the black hole has filled. 81 00:07:23,080 --> 00:07:26,770 Black holes are rotating. They're always cur black holes. 82 00:07:26,770 --> 00:07:33,009 They always have some angular momentum. And how much the rotating is quantified by this finger's spin parameter. 83 00:07:33,010 --> 00:07:38,080 A star I'm always going to call the axis on this the I right. 84 00:07:38,260 --> 00:07:41,920 A star is a different thing. It's the spin parameter for black holes. 85 00:07:42,040 --> 00:07:46,240 And this is the angular momentum of the black hole divided by G. Newton and the mass of the black hole square. 86 00:07:47,050 --> 00:07:52,030 And this is a useful variable because I start being zero means they're not rotating at all. 87 00:07:52,300 --> 00:07:56,500 An ice star equals one. Is maximum rotation the maximum you can ever rotate? 88 00:07:56,710 --> 00:08:02,860 This is where effectively the black hole horizon velocity is is the speed of light right going around. 89 00:08:03,370 --> 00:08:10,509 And we know from measurements this is for galactic sort of mass, this is for ten to the six up to ten to the nine. 90 00:08:10,510 --> 00:08:13,450 So low mass black hole so so galactic centre black holes. 91 00:08:13,930 --> 00:08:19,540 People have done measurements, this band parameter and you see that a very often very high above 0.9. 92 00:08:20,170 --> 00:08:23,530 Right. Some of them up to a point. 6.8. Right. 93 00:08:23,650 --> 00:08:30,910 And so we know, in fact, there many black holes are in fact relativistic, like rotating, which is a quite incredible thing. 94 00:08:34,040 --> 00:08:38,750 So black holes contain a huge amount rotational kinetic energy. 95 00:08:40,100 --> 00:08:46,520 It's a wonderful, remarkable fact with this angular momentum they have and this rotational kinetic energy can be extracted. 96 00:08:47,530 --> 00:08:56,440 From a black hole. In fact, of our very good friend Roger Penrose show that there is this classical Penrose process 97 00:08:57,220 --> 00:09:01,000 and its close relatives and it can extract energy that he was proposing back in, 98 00:09:01,000 --> 00:09:09,399 I think, late 1960s when I wrote this paper that maybe advanced civilisations would power their civilisation by doing this process, 99 00:09:09,400 --> 00:09:13,910 sending in stuff, gathering things, split, extracting the energy, setting angular momentum. 100 00:09:13,910 --> 00:09:19,840 And maybe this our balance of power relations ultimately would power themselves. However, I'm not interested in this process. 101 00:09:20,770 --> 00:09:24,070 I'm interested in a remarkable quantum process that occurs. 102 00:09:24,760 --> 00:09:32,919 So if you have a non-zero mass, it's very important that it's not exactly zeroth, a non-zero mass feebly interacting. 103 00:09:32,920 --> 00:09:36,230 That's also important. It can't be too strongly self interacting. 104 00:09:36,700 --> 00:09:42,399 Right. Bose on. So Bose wants let me remind you of spin zeros and ones with two in each of our equals one 105 00:09:42,400 --> 00:09:48,400 units and most historians and I'm going to say H by two one and C equals one just to drive, 106 00:09:48,400 --> 00:09:55,180 you know, many of you crazy as the units in which I think and I'll put some balances back right at the very end, 107 00:09:55,780 --> 00:09:58,179 then there's a process called quantum super radiance. 108 00:09:58,180 --> 00:10:02,050 In fact, super radiance, the thing that occurs in many, many different domains and has many different guises. 109 00:10:02,350 --> 00:10:08,770 But I'm going to talk about a particular thing. So what does this quantum super radiance in words do for you in a black hole environment? 110 00:10:09,310 --> 00:10:12,190 Well, what it does it say is a cloud of both zones. 111 00:10:12,550 --> 00:10:22,890 In a nonzero angular momentum, bound states around the black hole grows exponentially, actually, due to a form of lasing instability of this curve. 112 00:10:22,900 --> 00:10:26,860 Black holes. You start off with this curve, black hole. Let me show you in pictures. 113 00:10:27,580 --> 00:10:32,260 All right. Here it is. Here's my black hole. It's got some large angular momentum. 114 00:10:32,260 --> 00:10:35,710 It's highly spinning. Spin parameter is near one. All right. 115 00:10:36,130 --> 00:10:46,620 And what happens is there's a quantum instability of this where a cloud in a bound state of like feebly interacting particles. 116 00:10:46,630 --> 00:10:49,570 Ross actions is formed outside the black hole. 117 00:10:49,570 --> 00:10:56,940 And this thing extracts most of the angular momentum of this initial object, not all of it, and extract some percentage of the mass. 118 00:10:56,940 --> 00:11:00,909 So the initial mass energy of this black hole and puts it in this region exterior. 119 00:11:00,910 --> 00:11:06,970 And so the end situation is some part of the original mass has gone into the cloud and a lot of the angular momentum has gone into the cloud, 120 00:11:07,750 --> 00:11:12,850 this axial cloud. Okay, this is quantum super radians for spinning black holes. 121 00:11:12,850 --> 00:11:17,080 Now why does it occur? So I can say this a little bit more mathematically. 122 00:11:17,410 --> 00:11:26,650 And the reason is this. If you study the the quantum mechanics of a massive Bose field right in a black hole background, 123 00:11:26,920 --> 00:11:35,200 you find that it has bound states with with where they don't have purely real energy eigenvalues. 124 00:11:35,800 --> 00:11:40,840 All right. Remember, if I take you back also to trigger warning, second quantum mechanics, 125 00:11:41,500 --> 00:11:49,450 hamiltonians emission or the eigenvalues of the emission operator are real subtly because of the weird boundary conditions that black holes have. 126 00:11:49,810 --> 00:11:51,370 They're absorbing boundary conditions. 127 00:11:51,370 --> 00:11:58,389 This Hamiltonian of the system is not emission, and correspondingly you can have imaginary parts to its eigenvalues. 128 00:11:58,390 --> 00:12:08,230 And in fact it has an imaginary part of the energy eigenvalues which is positive, right is gamma is and the decay rate is negative, KMP is negative. 129 00:12:08,500 --> 00:12:14,560 And this leads when you write down mode squared or the Y function to exponential growth in time 130 00:12:15,160 --> 00:12:20,680 of this this cloud because we're solving this weird non commission quantum mechanics problem, 131 00:12:21,100 --> 00:12:24,190 this, this behaviour was first realised by these people. 132 00:12:25,120 --> 00:12:30,250 Press them to tell it to Koski and to more and zeros Erdely and Detweiler and various other people. 133 00:12:30,340 --> 00:12:35,350 They thought this was just an interesting, formal, you know, statement quantum mechanics in this background. 134 00:12:36,990 --> 00:12:42,000 An important part of this thing is these states here, the spatial wave function here. 135 00:12:42,000 --> 00:12:46,770 So this is exponentially growing. But this spatial other state is very similar to the. 136 00:12:47,040 --> 00:12:50,580 L greater than zero orbitals in the hydrogen atom. 137 00:12:50,910 --> 00:12:56,129 Looks like these you know these beautiful diagrams I'm sure you see when you do quantum mechanics, the hydrogen atom or chemistry. 138 00:12:56,130 --> 00:13:00,210 Quantum chemistry, they look like atomic orbitals, right of non-zero l. 139 00:13:02,330 --> 00:13:05,420 Now. Why does this occur? All right. 140 00:13:05,420 --> 00:13:10,930 Why does this feature occur? So here is a particular coordinate system called the tortoise core, 141 00:13:10,940 --> 00:13:14,210 and that which is very useful describing because it's right outside a black hole horizon. 142 00:13:14,390 --> 00:13:17,780 So the black horizon is way, way off into the left here. 143 00:13:18,230 --> 00:13:26,960 And here is the potential a massive particle sees in this in this background, when you translate it to an equivalent quantum mechanics problem. 144 00:13:27,810 --> 00:13:34,709 Right. So what happens is this region here, the ergo region, which Roger Penrose used to do, is classical energy extraction. 145 00:13:34,710 --> 00:13:41,790 And Anglo American extraction is a barrier region. This barrier is due to states having nonzero angular momentum and also L.Z. 146 00:13:42,690 --> 00:13:46,470 All right. So, you know, the Z component, the Angela mentum operator as well, 147 00:13:46,740 --> 00:13:53,500 and this this cool Coulomb like rise of the potential here is due to the mass of the particle. 148 00:13:53,520 --> 00:13:56,580 So so if a mass was zero, this wouldn't be this rise wouldn't be there. 149 00:13:56,940 --> 00:14:03,420 So what you see is because of the combination, this barrier and this rise, there's a little well here. 150 00:14:04,050 --> 00:14:07,860 All right. Which is interesting. And when you compute the quantum mechanics, this problem, 151 00:14:07,860 --> 00:14:13,979 what you find is you find quantum fluctuations of the of the Axion or whatever feeble interacting light particle you have 152 00:14:13,980 --> 00:14:21,450 here called sort of anti tunnel or tunnel through this barrier region and lead to this exponential growth of bound states, 153 00:14:21,690 --> 00:14:27,840 which have a tiny, tiny little tile here in this region here. But in fact, the dominantly located in this potential well region. 154 00:14:28,170 --> 00:14:36,720 So this is if you're thinking about short SR radii, this is sort of like one and a half to two short, short radio away from the black horizon. 155 00:14:36,990 --> 00:14:43,260 So a black hole that size, this size, this cloud is sitting a little bit outside, right in a region displaced from this. 156 00:14:43,260 --> 00:14:46,860 And you find this is exponentially growing. Right. 157 00:14:46,860 --> 00:14:57,759 This this this wave function. So you can calculate the analytically, numerically the growth rate for all the various atomic bound states, 158 00:14:57,760 --> 00:15:03,280 a function of the black hole speed parameter. And what you find is you always find the fastest growth rates for high speed. 159 00:15:03,910 --> 00:15:07,120 The growth rate goes down a lot as you lower the spin. 160 00:15:07,480 --> 00:15:18,219 So I'll show you that in a second. It also is a function of the the mass of your light particle times, the gravitational radius of of your black hole. 161 00:15:18,220 --> 00:15:21,820 Remember it spinning. It's not quite the short of radius, but something like it, basically. 162 00:15:21,820 --> 00:15:27,160 It's this, though. That's the thing. This is a dimensionless number, this thing of a mass times a distance. 163 00:15:27,230 --> 00:15:34,960 So you can think of this also as a ratio of the short, short radius of the black hole to the Compton wavelength of your particle. 164 00:15:35,320 --> 00:15:42,070 And what you find here. So here is log scale of this growth rate normalised to the mass, right? 165 00:15:42,070 --> 00:15:46,510 And so you see this thing is varying as you vary. Various things are here on this scale. 166 00:15:46,510 --> 00:15:52,570 Here is increasing axial mass linear scale. So here is 0.1.5. 167 00:15:52,810 --> 00:16:03,490 Here is point two, here is 1.8 varying the axial mass varying this ratio of gravitational radius of of the black hole to the same wavelength. 168 00:16:03,640 --> 00:16:07,840 And you see you quick, very quickly grow and then you fall off. 169 00:16:08,470 --> 00:16:13,420 That's a so optimal region you get. This is four different bound states. 170 00:16:13,420 --> 00:16:18,969 The leading state, the one where you super radiantly produce most is the l equals one. 171 00:16:18,970 --> 00:16:22,690 M equals one state, the simplest of the hydrogen like orbital. 172 00:16:23,650 --> 00:16:31,750 And then as you increase the black hole spin. So these colours here, this is the really high speed black holes like 0.99, you know, 173 00:16:31,780 --> 00:16:39,450 and it's like go down in spin then the growth rates decrease with I said so the dominant thing is I, 174 00:16:39,570 --> 00:16:52,840 I dominantly produce acciones will be when the mass is is about 0.4 right of inverse gravitational radius of my CO and 175 00:16:52,840 --> 00:16:59,130 I dominantly produce the things when the black hole is my spinning and I slow down a lot as I move away from my spin. 176 00:16:59,920 --> 00:17:09,700 Okay so this the bottom line of this is this is only a fast process for a massive field with Compton wavelength close to the black hole size. 177 00:17:10,180 --> 00:17:11,200 Right. That's the answer. 178 00:17:12,440 --> 00:17:18,800 In fact, you can look at the two previous timescales, how how for astrophysical black holes, how quickly does this process occur? 179 00:17:18,980 --> 00:17:25,010 Let me look at the high spinning highs we saw. We know that black and centre, black holes of high speed and things like this. 180 00:17:25,020 --> 00:17:31,309 So let's look at this high speed case and you find an optimal match between inverse Compton wavelength and the gravitational right, 181 00:17:31,310 --> 00:17:39,770 as when this thing is about point four for the leading atomic so bound state, and this timescale turns out to be this. 182 00:17:39,770 --> 00:17:44,180 I've written this and C equals one unit so length so the same as times here. 183 00:17:44,480 --> 00:17:50,480 So it's about it's almost 10 million times the light crossing time of the black hole. 184 00:17:50,870 --> 00:17:58,189 So in terms of the natural timescale of the black hole, light crossing time of the black hole, this takes a million times or 10 million times longer. 185 00:17:58,190 --> 00:18:05,260 So it's slow. But compared to astrophysical and cosmological timescales, in fact, this is very show. 186 00:18:05,620 --> 00:18:13,980 This is as short as 100 seconds. Right. Compared to the age of the universe, which is ten to the 17, you know, ten to the 18 seconds. 187 00:18:13,990 --> 00:18:19,990 Right. Or or accretion, which takes the place of a black hole ten to the 15 seconds. 188 00:18:20,200 --> 00:18:25,659 So this is a very fast process compared to the universe or anything. 189 00:18:25,660 --> 00:18:26,890 Astrophysical, right. 190 00:18:27,040 --> 00:18:33,520 And it happened, but it's a slow process as far as kind of minimal timescale it could be, which is like crossing time for the black hole. 191 00:18:34,340 --> 00:18:42,760 And as you go away from this optimal coincidence here, you either get exponentially suppressed or polynomials suppressed. 192 00:18:43,270 --> 00:18:50,050 All right. And that's what you were doing. These are the analytic formulas you can derive according to the graphs previously. 193 00:18:50,710 --> 00:18:55,090 So bottom line for this is you get fast, black hole spin down. 194 00:18:55,540 --> 00:19:01,130 If there exists a boson of the right mass and right mass means, you know, 195 00:19:01,270 --> 00:19:07,870 close to this and you can go refactor a few less and a few greater and still have a fast enough spin down. 196 00:19:07,880 --> 00:19:15,250 But once you go say a factor of 100 either away from this, then the spin down rates become so low they don't occur in the age of a galaxy. 197 00:19:17,830 --> 00:19:27,159 All right. Now, Astro black holes have have radii between a few kilometres and 10 to 13 kilometres so they 198 00:19:27,160 --> 00:19:34,120 can thus act as both produces via this quantum super irradiance instability and detectors. 199 00:19:34,270 --> 00:19:37,600 And you'll see how you might do that in a second of light both zones. 200 00:19:38,020 --> 00:19:46,030 And if you match these radii up with these with the masses to get this coincidence in Compton wavelength and radii, 201 00:19:46,210 --> 00:19:49,990 you find between ten to the -20 V and ten to the -21 Eevee. 202 00:19:50,440 --> 00:19:59,680 So it's 11 orders of magnitude in mass where any light particle which is weakly interacting as long as it's strictly massive, 203 00:20:00,010 --> 00:20:03,220 you can produce and try to detect by this process. That's very remarkable. 204 00:20:06,550 --> 00:20:13,150 But let's step back. Let's ask what this is. This thing is done for us. So what we've ended up with, if you think about this, 205 00:20:13,150 --> 00:20:20,260 is we've ended up with a quite extraordinary statement that there should or can exist gravitational atoms in the sky. 206 00:20:21,200 --> 00:20:26,329 Right. But rather than having, as you would have for a normal atom with electrons, we would only have. 207 00:20:26,330 --> 00:20:32,080 So you can see to spin up and spin down electrons in each possible orbital because these are both states. 208 00:20:32,500 --> 00:20:35,800 Now you can have arbitrary large occupation numbers. 209 00:20:35,810 --> 00:20:40,790 In fact, they're favoured right by Bose in usual Bose statistics argument. 210 00:20:40,930 --> 00:20:45,580 In fact, the occupation numbers of this leading state can be as high as ten to the 77. 211 00:20:46,730 --> 00:20:50,270 All right. Truly vast occupation numbers. All right. 212 00:20:50,270 --> 00:20:54,590 In this in this leading state carrying possibly four galactic black holes, 213 00:20:55,100 --> 00:21:02,750 ten to the eight solar masses worth of mass energy and true and truly vast amounts of angular momentum to. 214 00:21:06,250 --> 00:21:09,850 Now, as I said, it's rather important. I didn't mention this caveat. 215 00:21:10,090 --> 00:21:16,389 It's rather important that actually just particles of people interacting, if you turn on self interactions of these bosons or interactions, 216 00:21:16,390 --> 00:21:23,920 these photons with other things, in fact, this this exponential growth of this bounced light outside the black hole could be quenched, right? 217 00:21:24,100 --> 00:21:28,420 And so you can limit the cloud to small occupancy and you don't get any interesting signals. 218 00:21:28,870 --> 00:21:35,110 So you only get this maximal process going up through these kinds of occupation numbers for feebly interacting bosons. 219 00:21:35,470 --> 00:21:40,660 And of course axioms are a they are probably a leading example of something that we 220 00:21:40,660 --> 00:21:46,150 think is should be very light but but not exactly massless and also feebly interacting. 221 00:21:46,360 --> 00:21:49,749 Right. That's why this is an incredible possibility for action. 222 00:21:49,750 --> 00:21:53,639 Such as. So I've argued to you. 223 00:21:53,640 --> 00:21:57,690 The Astro Blanco should can have clouds around them. 224 00:21:58,950 --> 00:22:04,800 Containing lots angular momentum and a fair amount of mass. All made up of these actions in this cloud like configuration. 225 00:22:04,830 --> 00:22:08,250 Well, okay. So what does this cause for you? Right. 226 00:22:08,340 --> 00:22:15,060 How do you see this? What do you do with the test? Well, one test is if you now look at the spin of the black hole itself, 227 00:22:15,660 --> 00:22:19,590 there should be regions as you as you look at black holes with different masses. 228 00:22:20,050 --> 00:22:22,010 Right. If a black hole happened to be in the region, 229 00:22:22,050 --> 00:22:28,200 has this nice fluorescence effect with an axis on the Compton wavelength that all those micro should be spun down. 230 00:22:28,230 --> 00:22:32,790 You shouldn't see any high spin guys. For certain regions of black hole mass. 231 00:22:32,820 --> 00:22:35,820 There should be always gaps in the black hole mass. 232 00:22:37,530 --> 00:22:40,680 Spin plot. Right. Another thing is this. 233 00:22:40,690 --> 00:22:45,210 Well, zoned cloud now modifies the metric around the black hole. 234 00:22:45,420 --> 00:22:52,650 It's a black hole in an environment where I've put a lot of mass and angular momentum out there in a quantum state out there outside of my call. 235 00:22:52,830 --> 00:22:56,610 And of course, we are seeing black hole mergers through advanced lingo. 236 00:22:56,850 --> 00:23:02,580 And so if I have, you know, one of these two black holes has this cloud around it and the second black hole spirals in. 237 00:23:02,880 --> 00:23:06,270 In fact, you would change the spiral signal in delicate, interesting ways. 238 00:23:06,630 --> 00:23:11,730 That's another thing you can see. Another thing you could say is just like Joe spoke about in his talk, 239 00:23:12,120 --> 00:23:18,570 you could get actions if there's magnetic fields around and there's many fields all over the place in in astrophysics. 240 00:23:18,930 --> 00:23:22,830 Right. Then you can get Axion photon conversions. 241 00:23:23,550 --> 00:23:29,790 Now, these photons turn out to be of a sort of annoying frequency, very often hard for us to see on earth. 242 00:23:30,000 --> 00:23:35,280 But do we ever have good radio telescopes on the surface of the moon, dark side of the moon, which be a wonderful thing. 243 00:23:36,540 --> 00:23:39,600 Maybe that's a good reason to have a moon base. I mean, other things. 244 00:23:39,930 --> 00:23:43,860 Just talk to Elon Musk and get him to fund this. We have a radio telescope. 245 00:23:44,340 --> 00:23:47,370 We have that possible for us to see such things. That's another possibility. 246 00:23:48,770 --> 00:23:55,430 But one of the one of the really, really striking things you could see is you could say monochromatic. 247 00:23:55,880 --> 00:24:03,890 So not a broad spectrum of gravity waves is what we now see in advance logo but monochromatic gravity waves from stellar mass black holes. 248 00:24:05,070 --> 00:24:13,520 Right. And the idea here and this was mentioned in our original paper and then studied in a very beautiful follow up paper by Mina and Serguei. 249 00:24:13,940 --> 00:24:20,149 In this paper here, you can have these actions, a member or an l equals one orbitals, right? 250 00:24:20,150 --> 00:24:28,639 So one unit of each bar of an aluminium each. You can have two axioms meeting this means the so background metric background gravitational 251 00:24:28,640 --> 00:24:32,930 field of the black hole and you can have a process with two actions in this background. 252 00:24:32,930 --> 00:24:40,380 Gravitational field can produce a graviton. This graviton carries off two units of angular momentum to a bar that agrees with the two. 253 00:24:40,580 --> 00:24:41,959 What I get from these two axioms, 254 00:24:41,960 --> 00:24:48,620 each in the open line commitment states and the graviton energy is at essentially twice times of the mass of the Axion. 255 00:24:48,620 --> 00:24:52,699 And you get this monochromatic line, right, which is this sort of frequency, 256 00:24:52,700 --> 00:24:59,210 ten kilohertz going down and going down to lower frequencies as you make the axial mass less and less and less. 257 00:24:59,900 --> 00:25:05,540 So this and in fact, you could possibly see these lines even in quite distant black holes. 258 00:25:05,840 --> 00:25:13,520 And this is an incredible possibility for the next generation of gravity waves, detectors, that humanity is building different frequency ranges. 259 00:25:14,240 --> 00:25:19,460 So the signal enhanced, well, one, you might think, oh, god, how could how could this ever be a fast process? 260 00:25:19,790 --> 00:25:24,290 You know isn't there you know factors of one over implying Koji Newton here that's making is really slow. 261 00:25:24,470 --> 00:25:31,490 Well yes but that's true but the the occupation number of these initial states a huge ten to the 77 262 00:25:31,820 --> 00:25:38,780 and these ten to the 70 sevens in fact enhance this signal by square of this state occupation number. 263 00:25:39,260 --> 00:25:43,670 So even though this is a this is a almost a quantum this is a quantum gravity process. 264 00:25:43,700 --> 00:25:47,300 You're producing a quantum of gravity gravitation here. 265 00:25:47,570 --> 00:25:51,080 In fact, it's enhanced by the incredibly large occupation numbers. 266 00:25:51,900 --> 00:25:57,180 Right. So that would be another amazing thing. So you could see like vast numbers of that. 267 00:25:57,230 --> 00:26:01,250 You'd be seeing actions, you'd be see you can some aspects of quantum gravity, 268 00:26:01,250 --> 00:26:05,360 you'd be doing other tests, you know, you'd be doing something once you saw monochromatic. 269 00:26:05,480 --> 00:26:09,740 Let me remind you that we get an immense amount of information about our universe, our world. 270 00:26:10,280 --> 00:26:14,900 One of the reasons is from observations of spectra. 271 00:26:15,170 --> 00:26:18,350 One of the great things is that Spectra is discrete. All right. 272 00:26:18,560 --> 00:26:22,280 The fact that we saw Obama theories and other things all over, you know, in the universe, 273 00:26:22,280 --> 00:26:25,849 we saw it in our sun and we saw it in distant stars, and we can match things together. 274 00:26:25,850 --> 00:26:29,629 We could get a tremendous amount of information from the redshift, bit of hints and other things. 275 00:26:29,630 --> 00:26:31,880 This discrete. This is another extraordinary thing. 276 00:26:33,410 --> 00:26:42,290 Well, there's many, many other signatures of of axioms in astro cosmological environments being an activity by groups all across the world. 277 00:26:42,320 --> 00:26:46,460 It's really quite extraordinary. Rich Field And Joe has already told you about some of the things you can do. 278 00:26:46,910 --> 00:26:54,890 But I now want to turn from the sky to the basement, including our basement here in in Clarendon and in the Beecroft. 279 00:26:56,150 --> 00:26:59,000 So this is going from this is the black hole spins thing. 280 00:26:59,000 --> 00:27:04,340 I've just told you this constraint which carries on down here, and then there's this region here. 281 00:27:04,760 --> 00:27:11,870 Right. So I want to tell you about that. So how do we search for feebly interacting actions in labs? 282 00:27:12,770 --> 00:27:19,580 Well, the interactions of the leading interactions of actions with ordinary matter come in three basic forms. 283 00:27:20,000 --> 00:27:26,450 There's a thing that both Joe and Sid told us about, which is the action a dot be interaction with electronic and be filled. 284 00:27:27,530 --> 00:27:35,060 There's also an interaction of the grade into the Axion with Fermi on spin, whether these could be any fermions electron, proton, neutron. 285 00:27:35,240 --> 00:27:39,380 Notice the gradients. This is about some sort of Axion variation. 286 00:27:39,950 --> 00:27:43,520 All right. Sometimes it's called the second wind coupling. 287 00:27:43,970 --> 00:27:51,430 And then finally, there's this thing which is special for the quick action, which you can give a thing which is dependent on the electric field. 288 00:27:51,440 --> 00:28:01,580 This is an electric field that the nucleons spin. And this can give what will be a varying or time varying electric dipole moment of some objects. 289 00:28:01,970 --> 00:28:04,280 Right? So these are three basic things. 290 00:28:04,910 --> 00:28:12,830 All of these couplings G, Gamma, Gamma, GIF and GBM, all of these couplings go like one over this far, this large scale. 291 00:28:12,870 --> 00:28:17,420 They're all very tiny couplings. All right. But this is the sort of form that they have. 292 00:28:18,380 --> 00:28:26,250 Now, the most commonly used coupling is this action in dot B, electric field, dot magnetic field term. 293 00:28:26,270 --> 00:28:30,500 And I'm going to talk about this to both Sid and Joe mentioned this, so I'm going to talk about the use of this. 294 00:28:31,040 --> 00:28:34,550 So I want to give you some little bit more intuition for this term. 295 00:28:35,090 --> 00:28:38,120 So there are various ways of thinking about this, this term. 296 00:28:38,840 --> 00:28:48,799 So if if both I, the Axion and the and B fields are well described as classical fields, of course, we always usually think of EMG as classical fields. 297 00:28:48,800 --> 00:28:50,150 But of course, you know, this photons, 298 00:28:50,150 --> 00:28:56,719 we could in principle have discrete packets of of of electromagnetism as well as the continuous classical fields. 299 00:28:56,720 --> 00:29:02,900 But if there is the world's most classical fields, then this new term here, this term modifies a Sid. 300 00:29:03,210 --> 00:29:06,590 Explain two of Maxwell's equations and you get Axion electronics, 301 00:29:07,220 --> 00:29:12,980 which I believe was first written down by C Kivi and then we'll check over a series of papers and study and here it is. 302 00:29:12,980 --> 00:29:19,460 Here the there's two Maxwell equations that stay exactly the same and then you get these two mode of modified Maxwell equations. 303 00:29:19,850 --> 00:29:24,200 So this is Dave of the electric field is the normal charge density. 304 00:29:24,410 --> 00:29:29,480 So Rho and J here just the normal charge density and current of normal matter. 305 00:29:29,660 --> 00:29:32,690 And you get these extra affective terms. Here we go. 306 00:29:32,690 --> 00:29:40,519 Like, gee, I'm a I'm at times derivative of the Axion rather the action dot B or this thing here time to reflect sometimes B and then this thing, 307 00:29:40,520 --> 00:29:43,670 which is a curl. All right. Okay. 308 00:29:44,450 --> 00:29:47,560 So what does this mean? Well, if you think about this, 309 00:29:47,860 --> 00:29:54,669 I could define as an experimental is I could define everything that occurs on the right hand side of this equation is an 310 00:29:54,670 --> 00:30:00,160 effective charge density and everything occurs on the right hand side of this equation is an effective current density. 311 00:30:00,670 --> 00:30:04,900 So what it says when I think about this in the presence of any field, 312 00:30:05,260 --> 00:30:12,730 the action is a new kind of charge density which is this and a new kind of current density, which is that. 313 00:30:12,970 --> 00:30:16,930 And you could try to look for these new types of charge density and current density. 314 00:30:18,750 --> 00:30:25,770 On the other hand, that was for classical things. If one or more of Axion or the field of the B field is the quantum limit, 315 00:30:26,070 --> 00:30:31,590 so Axion control and or photons, then it's useful to think in terms of Feynman diagrams. 316 00:30:32,540 --> 00:30:39,620 And here's a FINEMAN diagram game. Joe, use this. So here's the incoming action of Quantum of Energy Omega. 317 00:30:39,920 --> 00:30:44,060 Here's a background classical B field. All right. 318 00:30:44,450 --> 00:30:48,950 The reason why I'm going to focus on the B field cases that large B fields are very easy to produce in the laboratory. 319 00:30:49,370 --> 00:30:52,700 Large E fields are hard to produce in the laboratory, at least macroscopic ones. 320 00:30:53,420 --> 00:30:58,050 So here's a large B field, and then this, then this new terminal constant. 321 00:30:58,070 --> 00:31:06,920 I b gives you a new Feynman diagram, which is Axion quanta comes in and produces an outgoing photon of energy omega. 322 00:31:08,290 --> 00:31:11,980 Okay. So you get axial photon conversion, as Joe described. 323 00:31:14,720 --> 00:31:19,850 So we can try to use this coupling to try to detect actions. 324 00:31:20,780 --> 00:31:26,569 So these are very. So one possibility is we detect these very tiny new charges in current cells by the 325 00:31:26,570 --> 00:31:32,510 actual field of presence of A and B side by detecting anomalous heating of a cold, 326 00:31:32,510 --> 00:31:37,460 shielded cavity, I give you a cold shoulder cavity and I say that some sort of axial is coming in 327 00:31:37,790 --> 00:31:41,330 and it should be dumping because it generates currents and electric charges. 328 00:31:41,430 --> 00:31:45,440 It should be dumping electromagnetic energy inside this cold cavity. That's one thing. 329 00:31:45,830 --> 00:31:54,979 There's there's also the quantum version of that. Or almost equivalently, you try to detect these very rare photons that are being produced. 330 00:31:54,980 --> 00:32:04,910 So by Axion Quanta in the presence of the B here you detect anomalous photon counts in a cold shielded cavity. 331 00:32:05,360 --> 00:32:12,710 Okay, so this is the idea. But there's one major thing I haven't told you yet, which is where do these actions come from? 332 00:32:12,730 --> 00:32:17,040 Where do these initial axioms come from? In a black hole case, the black hole itself producing axioms. 333 00:32:17,810 --> 00:32:23,110 Right. But I'm assuming I don't have a spare black hole just hanging around the lab that we great piece of equipment to have. 334 00:32:23,110 --> 00:32:31,899 But sadly, you know. So one very important possibility is the axioms could occur naturally be produced in the early universe. 335 00:32:31,900 --> 00:32:37,900 And this was studying two very beautiful papers by press, quoting wires and evidence giving back in the early eighties. 336 00:32:38,290 --> 00:32:45,540 In fact, the QC, the Axion and also Axion like particles are probably now a leading candidate for dark matter. 337 00:32:45,550 --> 00:32:50,170 They could be the dark matter. And I'm not going to tell you about all of these dark matter production mechanisms. 338 00:32:50,470 --> 00:32:57,160 That would be an entire other talk. All right. Actually, many talks, but I'm just gonna say it does exist. 339 00:32:57,160 --> 00:33:00,340 There's a beautiful set of mechanisms. It would use axioms. Does that not matter? 340 00:33:00,340 --> 00:33:05,889 And it could be. That's what they are. Ex-cons are excellent automatic candidates as they're very feebly interacting. 341 00:33:05,890 --> 00:33:09,190 So that dark. Right. And that's what we mean by dark. 342 00:33:09,490 --> 00:33:16,260 They're very long lived. They're still around today. I don't care why that would be bad if we had lots of decaying dark matter. 343 00:33:16,260 --> 00:33:20,710 You'd already gone. And they have nice production mechanisms that leave them cold. 344 00:33:20,830 --> 00:33:27,760 That's important. That means cold means non relativistic, the moving non relativistic clean out around in our galaxy and in our universe. 345 00:33:27,910 --> 00:33:33,730 And that's necessary for successful galaxy formation. So axioms are great dark matter candidates. 346 00:33:34,420 --> 00:33:37,540 However, there's one thing I should say that's important to bear in mind. 347 00:33:38,050 --> 00:33:45,070 The Axion dark matter is better described not as individual, usually think of dark matter as being lots of particles moving around. 348 00:33:45,120 --> 00:33:48,550 Occasionally it hits you or one of your nuclei and you get some signal. 349 00:33:48,970 --> 00:33:55,209 But in fact, because these actions are so light as you just create the mass of dark matter, 350 00:33:55,210 --> 00:34:00,760 since we know it has a different given mass density as you decrease the mass of these particles, 351 00:34:01,030 --> 00:34:09,530 given the fact you had a fixed mass density to be the dark matter, the number density has to go up and more of these particles. 352 00:34:09,550 --> 00:34:14,890 And moreover, as you decrease that mass their Compton wavelength and also the de broglie wavelengths get longer and longer. 353 00:34:15,130 --> 00:34:22,480 So as you just create this mass of the particles, what happens is they're the broad wavelengths very strongly overlap with each other. 354 00:34:22,660 --> 00:34:30,370 And this limit when you have a very, very large occupancy per quantum state, the way of saying this is best described as a field. 355 00:34:31,180 --> 00:34:39,220 So in fact, here is the sort of a plot of the of bosonic dark matter landscape wearing with mass is normal wimps. 356 00:34:39,760 --> 00:34:45,280 These are now slightly disfavoured and here all the way down from one ivy down to ten to the -22. 357 00:34:45,280 --> 00:34:50,710 B If you have bosonic dark matter in this range, then it's best described as the classical field. 358 00:34:51,760 --> 00:34:58,280 Right. And it's because the number density which is given by this is much, much bigger than one over the wavelength. 359 00:34:58,790 --> 00:35:03,620 Right. And this is when the mass of the particles is about roughly less than one anything. 360 00:35:04,540 --> 00:35:09,620 Right. So this should be described. You should think of dark matter as a classical field that everyone. 361 00:35:10,930 --> 00:35:13,360 Now. What is it? Friends, it's everywhere. 362 00:35:13,360 --> 00:35:21,370 Prisons is a classical field where these actions are known relativistic, so dominantly oscillates at a frequency set by just the mass. 363 00:35:21,670 --> 00:35:25,840 For the first time this talk I put back the C and H, right. 364 00:35:25,870 --> 00:35:30,159 I've turned it on. So here is the frequency term of the Axion field just generate mass. 365 00:35:30,160 --> 00:35:32,050 That's because it's basically almost stationary. 366 00:35:32,350 --> 00:35:43,600 It's not quite stationary though, because there is some known velocity dispersion of of matter in our galaxy. 367 00:35:43,990 --> 00:35:50,920 Right. And so this thing actually means that this field is not perfectly temporally and spatially coherent. 368 00:35:51,490 --> 00:35:55,330 It's a it's a quasi coherent Axion field. 369 00:35:56,140 --> 00:36:02,680 And moreover, this frequency that it's normally oscillating at again is this frequency by the axial masses. 370 00:36:02,740 --> 00:36:09,520 Amplitude. How about the amplitude of this field? It's set by square root of the dark matter density and the and the axial mass. 371 00:36:09,640 --> 00:36:15,430 We know reasonably well up to about a factor of two or three what the dark matter density is and all galaxy. 372 00:36:16,350 --> 00:36:21,310 Right. So here's a picture that I drew for some lectures I gave her. 373 00:36:21,590 --> 00:36:26,110 He is asked, moving through a random Gaussian field of of actions. 374 00:36:26,120 --> 00:36:30,889 And here is us on the earth, on some experimental lab, and we're moving through the galaxy. 375 00:36:30,890 --> 00:36:34,310 Our speed through the galaxy is roughly ten to the minus three at the speed of light. 376 00:36:34,610 --> 00:36:43,339 So we are moving slowly through this, slowly moving and varying quasi coherent action fields. 377 00:36:43,340 --> 00:36:48,170 This blue and the orange is supposed to do difference coherence patches of the axial. 378 00:36:48,860 --> 00:36:52,000 And here is a translation time between the mass. 379 00:36:52,010 --> 00:36:54,440 The action is frequency and experiment. 380 00:36:54,440 --> 00:37:01,700 We looking for the the coherence time experiment earth would have and here is the coherence length for these patches. 381 00:37:01,700 --> 00:37:11,780 So for instance, if I'm shooting an actions with ten to the -40 V, I get a coherence length which is sort of like maybe ten or a few metres. 382 00:37:12,150 --> 00:37:16,310 I get a coherence time, which is something like ten to the minus 4 seconds. 383 00:37:16,820 --> 00:37:20,270 Right. And I get a frequency which is sitting up at ten to the ten hertz. 384 00:37:20,840 --> 00:37:24,950 Okay. So ten gigahertz. That's the end of the dark matter. 385 00:37:24,980 --> 00:37:29,310 Almost done. So now we know where the Mexicans are coming from. 386 00:37:29,330 --> 00:37:33,080 They're coming from the dark matter. And they're not relativistic. They're slowly moving. 387 00:37:33,470 --> 00:37:37,640 So how exactly do you search for dark matter axioms when you search for dark matter? 388 00:37:37,820 --> 00:37:41,750 Well, it depends, actually. Which dark matter Axion, Mass you're looking at. 389 00:37:42,080 --> 00:37:46,670 Technologies vary a lot as you go from one frequency range to others. 390 00:37:46,700 --> 00:37:50,590 This comes from a very nice report that was done by the DOE a few years ago. 391 00:37:50,630 --> 00:37:51,470 Think about these technologies. 392 00:37:51,650 --> 00:38:00,390 So here gigahertz microwave cat is here a megahertz circuits magnetic resonance atom in parameters right here is on the it varies. 393 00:38:00,410 --> 00:38:04,370 In fact there's a very wide range of quantum technologies can be used to actually on detection. 394 00:38:05,120 --> 00:38:10,120 I'm going to focus on, well, two things. Oxygen's involved in microwave cavities and almond promises. 395 00:38:10,970 --> 00:38:14,720 And in fact, these are two of the leading technologies. I might tell you five times just one other thing. 396 00:38:15,320 --> 00:38:20,450 So here is the basic idea that comes from a basic initial proposal, security back in 83. 397 00:38:20,450 --> 00:38:26,749 But finally it's actually being realised and getting to the sensitivity you need to search for actions over a wide range. 398 00:38:26,750 --> 00:38:31,579 Here is a cavity you put on. A strong magnetic field is a classical, classical magnetic field. 399 00:38:31,580 --> 00:38:37,040 You keep this cavity extremely cold. All right. An axion comes in from the dark matter. 400 00:38:38,360 --> 00:38:46,340 You can think of it because it's a quasi coherent process. In fact, if you leave the experiment waiting for a while, you can build up the signal. 401 00:38:46,460 --> 00:38:52,670 Also, because this is a this thing is a quasi coherent field, almost oscillating at a single frequency. 402 00:38:52,970 --> 00:38:56,900 You can do high CU resonance enhancement of the signal. 403 00:38:56,900 --> 00:38:59,510 So we're going to use the fact is a high queue cavity as well. 404 00:38:59,810 --> 00:39:06,080 So you produce really a photon or another way of seeing that is you choose excess power. 405 00:39:06,290 --> 00:39:13,939 So what you do is you then using actually hopefully better than quantum noise, limited amplifiers, squeezed state things. 406 00:39:13,940 --> 00:39:17,540 You mix this thing down to a frequency and fast for your transform this and you see 407 00:39:17,540 --> 00:39:22,610 the power spectrum of this thing and you hope to see a little excess power somewhere. 408 00:39:23,890 --> 00:39:29,960 Right in this corresponding to the action, dumping, anomalous heating inside your cavity. 409 00:39:32,490 --> 00:39:37,810 Now. How can you tell if you saw a signal? It's not just some mess up, you know that some suspect. 410 00:39:37,950 --> 00:39:42,810 Well, this thing has. If you turn the field off, this signal should go away. 411 00:39:42,840 --> 00:39:46,319 That's one thing you can do. Another thing you can do is you focus. 412 00:39:46,320 --> 00:39:50,040 Once you start seeing some excess power, you do even higher IQ cavities. 413 00:39:50,040 --> 00:39:57,420 And now you can scan the line shape. And this line shape here actually is predicted to have a definite shape, not absolutely known, 414 00:39:57,630 --> 00:40:05,070 but this line shape depends upon this thing, which is the way that the galactic galactic velocity dispersion is. 415 00:40:05,360 --> 00:40:09,959 We know some things about this, not everything about this. So we have some idea about the line shape. 416 00:40:09,960 --> 00:40:10,200 In fact, 417 00:40:10,200 --> 00:40:18,420 there's a number of other tests you can do which could test that this was truly an action dark matter signal and not some sort of other systematic. 418 00:40:19,460 --> 00:40:27,780 Right. I want to emphasise this is resonant conversion of the axioms, which is why it's raining. 419 00:40:28,200 --> 00:40:32,640 So this is just like you exit excess v dependent power of a particular furniture. 420 00:40:33,240 --> 00:40:38,610 Now, how much power are we looking for? We're looking for extremely small access power. 421 00:40:38,910 --> 00:40:42,930 In fact, of accused. Here is the formula for the expected power. 422 00:40:42,960 --> 00:40:49,200 And one of these cavities. He's a 30 metre cavity. Quality factor of the cavity of ten to the five. 423 00:40:50,490 --> 00:40:56,700 I should say the sort of line of natural line width is expected to be about ten to the minus ten to the six to the minus six. 424 00:40:57,090 --> 00:41:05,460 So this is we are doing slightly broader than the actual line of ten Tesla magnetic fields, which you can now achieve. 425 00:41:06,160 --> 00:41:10,680 Here is the of the power expressed in terms of what the Axion frequency is. 426 00:41:10,680 --> 00:41:14,520 Let's say that one gigahertz is a particular choice that gives you the actual mass and you see, 427 00:41:14,520 --> 00:41:18,060 but this number is ten to the -23 or few times to the -23 watts. 428 00:41:19,070 --> 00:41:25,310 So this is incredibly small deposition or or if you want to take the vote on term, 429 00:41:25,550 --> 00:41:29,420 incredibly rarely do you see an excess photon sitting in your cavity. 430 00:41:30,590 --> 00:41:38,930 So it's obviously essential to maximise B field strength cavity parameters and very much minimising thermal and quantum noise. 431 00:41:39,470 --> 00:41:43,640 You have to go beyond really standard quantum limit to do this. 432 00:41:44,550 --> 00:41:50,160 But finally, over the last couple of years, the experiments worldwide are now reaching the sensitivity. 433 00:41:51,060 --> 00:41:54,420 The one fly in the ointment is that they're resonance searches. 434 00:41:55,080 --> 00:41:58,170 And that means you do one frequency band, which is pretty narrow. 435 00:41:58,740 --> 00:42:02,160 But we don't know where the axial mass is. So you have to step through. 436 00:42:02,340 --> 00:42:06,600 And at the moment with with it's just a flame consuming thing at the moment. 437 00:42:06,600 --> 00:42:12,540 The rate of scanning at the moment, we're going to take maybe tens of years to cover, you know, the full range. 438 00:42:12,780 --> 00:42:18,180 We would like to speed it up. So a lot of the ideas we're currently working on is how to do the scanning better. 439 00:42:18,620 --> 00:42:22,350 Right. And I'll show you one issue with the scanning right at the very end. Right. 440 00:42:22,410 --> 00:42:25,899 But we're getting there and. Now. 441 00:42:25,900 --> 00:42:27,500 Very nice final statements. 442 00:42:27,510 --> 00:42:35,290 Fortunately, the UK for a long time wasn't really seriously involved in this, this particular kind of actual search, to my great sadness. 443 00:42:35,740 --> 00:42:42,400 But in fact, we're now involved in a major project in the area called Quantum Sensors for the Hidden Sector, which I'm one of the theorists. 444 00:42:42,640 --> 00:42:44,980 I'm just a parasite on them. 445 00:42:44,980 --> 00:42:58,210 Clearly, the real people doing the work are people like Peter League and Boon ten, an experiment at Oxford and other experimentalists. 446 00:42:58,420 --> 00:43:00,160 In fact, this is our collaboration. 447 00:43:01,210 --> 00:43:07,660 This is a collaboration between Sheffield, Cambridge, Oxford Royal Holloway, Lankester, UCL National Physics Laboratory, Liverpool. 448 00:43:08,440 --> 00:43:16,629 Using incredible expertise we share as this combined group, we are hoping we've got a memorandum of understanding with IBEX, 449 00:43:16,630 --> 00:43:21,430 which is the current world leading experiment in this area, and we're going to build an even better facility. 450 00:43:21,430 --> 00:43:26,350 In fact, we've got government funding for this actually partially due to Ian, where Ian is. 451 00:43:26,530 --> 00:43:30,190 Thank you Ian. For, for pushing the government to actually provide. 452 00:43:30,940 --> 00:43:34,480 We course we went through a competitive review. It wasn't fixed or anything like that. 453 00:43:35,500 --> 00:43:41,470 We went through it. But the government actually provided £40 million for quantum technologies for fundamental physics. 454 00:43:41,910 --> 00:43:50,260 Right. And then we're using some about £7 million of this to do this, what we think is going to be a world leading to the actual out search, 455 00:43:50,260 --> 00:43:58,720 maybe also another type of hidden photon, a possible in a certain mass range, which is sort of complementary to the idea mixed mass range. 456 00:43:59,470 --> 00:44:05,440 So that's this here, this is actually a picture of the AB Max experiment when I mentioned the problem 457 00:44:05,440 --> 00:44:09,610 is is scanning how do they change the resonant frequency of the cavity? 458 00:44:09,820 --> 00:44:16,990 The way they do at the moment is you have these incredibly precisely machine bars that you physically move around in 459 00:44:16,990 --> 00:44:21,850 the cavity and this changes everything slightly the rest of the modes of the cavity and their resonant frequency. 460 00:44:22,060 --> 00:44:28,150 But this is a mechanical way of tuning, so you can imagine that you have to do these incredibly fine scans. 461 00:44:28,420 --> 00:44:33,370 This this is the real time, but this is the best thing that was known how to do this five years ago. 462 00:44:33,640 --> 00:44:39,730 We're now thinking about new ways of doing it, which are using quantum electronics to do the scanning. 463 00:44:40,180 --> 00:44:43,900 Okay. So that's a new progress. So this is my conclusions. 464 00:44:45,370 --> 00:44:47,529 As you've seen from all three of our talks, I hope, in fact, 465 00:44:47,530 --> 00:44:53,290 there is a vast number of new experiments and new theory ideas and axiom physics worldwide. 466 00:44:54,190 --> 00:45:00,399 In fact, I think this is one of the most exciting and active areas of all of combined theoretical experimental physics, 467 00:45:00,400 --> 00:45:06,430 and I wouldn't be at all surprised if there was some very interesting things happening in future years. 468 00:45:06,460 --> 00:45:08,860 I mean, big surprises. So please stay tuned. Thank you.