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  • those of you who follow us on Twitter or Facebook might know that our very own professor, Ed Copeland, recently won a prestigious medal from the Institute of Physics.

  • Now we're all really pleased.

  • It was a great excuse to go and have a night out and amazingly see Professor Moriarty in a bow tie.

  • Something you don't see every day.

  • Professor of the university.

  • But here it 60 symbols, of course, were especially happy for Professor Copeland.

  • Now, his wind has nothing at all to do with 60 symbols.

  • He's won it for his own research into three areas.

  • Cosmic strings and superstrings.

  • Inflation.

  • That's not the financial type.

  • Of course, we're talking on a cosmic scale here and dark energy.

  • So we're gonna post three videos, one on each area of research on I really let off the leash a bit here, so it's gonna be talking for quite a while, but I know a lot of you always say you want to hear more from the professor's.

  • So he ago.

  • Here's the first of three videos with head on.

  • This one is cosmic strings and super strength.

  • You know, when they announced the Nobel price on duh they announced it two Higgs and on Blair who quite rightly received the prize.

  • They didn't give it to Kimble, which, uh, upset me badly because Tom was a good friend.

  • But also, I think he probably deserved it as much as they did.

  • And so I tweeted a few minutes later and I said, You know, congratulations to Higgs non gleefully deserved by I feel sorry for Tom, and what we now need to do is gone.

  • Find cosmic strings so that he can get his own Nobel Price.

  • Because Tom Cable came up with the idea of cosmic strings back in 1976.

  • These wonderful objects.

  • First of all, you need a riel imagination to come up with these kind of things.

  • They're related to the Higgs field.

  • They are made up of what we could call the Higgs field, but just a completely different energy.

  • Sir.

  • Cosmic strings are examples of something called atop a logical defect.

  • These are objects that formed in the vet may have formed in the very early universe.

  • There's no evidence yet of their existence on DA.

  • They're incredible.

  • They're amazing objects.

  • And so I'll just try and describe give you an idea of them.

  • Their their strengths.

  • Their thickness is much, much smaller than a proton.

  • OK, so you've no chance of seeing them, but they can be a CZ long as the observable universe.

  • Moreover, if you had about a kilometer of such a string, it would have the mass of the earth.

  • So there is much thinner than a proton, but that the mass of the objects are the energy stored in the objects Would be of a kilometer of them would be about that of the Earth on dhe.

  • They could.

  • They formed these particular ones would have formed within the 1st 10 to the minus 35 seconds after the Big Bang.

  • You just need quite an imagination to think about these things on dhe they formed in the first transitions, just as we've been hearing about the Higgs field undergoes face transitions.

  • And as it undergoes this transition, where it changes from one state to another state, it can give masses to the particles.

  • In this particular case, what happens is that the equivalent field, but at a much higher energy as it changes from one high energy state to another under a first transition throughout the universe.

  • This doesn't happen all smoothly on DDE.

  • There are various parts of the universe where it were.

  • A bit of the original high energy bet gets trapped on these air formed the lines thes long strings so that the strings of the original high energy bit That was before the first transition on the surrounded by the new phase, which is at the lower energy on once they're formed, you haven't.

  • You have a network of these long strings crossing across the universe and loops of string on, then there because they're so massive.

  • And then there's so much tension they begin to flop around, and as they flop around, moving at close the speed of light or about half the speed of light, they begin to cross one another.

  • So you imagine a long piece of string like a shoe less Okay, imagine a shoelace and you as it wraps back and crosses itself.

  • But with a shoe less, you can't do anything.

  • It just can't go through itself.

  • But with a cosmic string, they can.

  • It can chop off at that point where where a piece of string crosses itself, Then at the junction where they've crossed it will break These loops of string now are under a huge tension.

  • Remember Kilometers, about the mass of the earth there are selecting around that.

  • Moving close to the have been a good fraction of the speed of light on because they're moving and oscillating, they radiate.

  • They radiate gravitational waves, just like any massive object that moves will radiate gravitational waves.

  • And that's its principal way of losing energy.

  • Because if they didn't do that, what would happen is the long strings would just keep Stretching as the universe expands is be like pulling an elastic band on the energy stored in these long strings would get bigger and bigger and bigger, and eventually they would come to totally dominate all the other contributions to the energy in the universe.

  • And it would completely change the dynamics of the universe.

  • So that doesn't happen.

  • We don't seen any, so either they're not there or something else has happened, which is meant they don't dominant on.

  • The thing that we think happens is that because these long strings conform loops on these loops can then radiate their energy and gravitational waves, Then they can reach what we call a stable scaling solution where the energy stored in the strings becomes a constant fraction of the total energy.

  • So it never comes to dominate the energy and the strings doesn't disappear.

  • It doesn't grow and become too big.

  • Just becomes like the Goldilocks amount of energy is just right.

  • And that was what got people very excited.

  • When Tom Cable first came up with this amazing idea of the formation of these objects, he demonstrated that when they evolve under the expansion of the universe that they were chop off these loops and they would radiate away their energies in just the right amount so that they overall energy of this network of strings would be some fixed fraction of the background energy.

  • Now it turns out you can work out what that fixed fraction is on it and use.

  • You find that for for first transitions which correspond to what we call the grand unified phase transition.

  • That's where we unify the strong electoral week and the electromagnetic forces.

  • This is about 10 to the minus 35 seconds after the big bang that the energy scale associated with that which determines the masses of these strings that is just sufficient to lead to the fluctuations in the matter that producers the cosmic microwave background radiation on the distribution of Galaxies.

  • This was what it seemed to be the case back in the 19 seventies and early 19 eighties, that cosmic strings provided that the seeds from which structures would fall so people so no, we had a theory which was rivaling another theory called the inflationary universe, but they were competing with one another.

  • Unfortunately, about the time I started working on these theories, um, they the evidence from the cosmic microwave background was coming in and it was getting better and better.

  • More accurate.

  • You could.

  • You could see the fluctuations in the temperature of the microwave background in all different sizes across the across the university observable universe.

  • And you could begin to fit your predictions from cosmic strings with what you observed in terms of what this distribution should be and you found cousin and it was found that cosmic strings just weren't working.

  • They were not matching the observed cosmic microwave background on our Satrapi's, and so people began to lose interest.

  • These wonderful objects that could well have formed in the early universe on, I should say that the analog objects that have been observed in converts, matter systems there, observed in liquid helium systems there observed insistence with dramatic liquid crystals, the scaling properties a roll scene and match what you might expect from cosmology.

  • It's just that they're not been senior in cosmology.

  • So back in the turn of the end of the 19 nineties beginning of 2000 people began to lose interesting these objects because they were not doing what they were, it said.

  • On the tin in particular, when you look at the observed map and look at the power in the map has a function.

  • If you like of the of the angle of the sky that you're looking at, it's got a very distinctive set of peaks and troughs.

  • They called the Doppler peaks and troughs.

  • When you compare that with what the prediction is from cosmic strings, basically, the cosmic strings would give you one peek.

  • Andi no, the second repeats not the Secondly Doppler Peaks I carried on because I was interested in some of the features.

  • There are some, as I mentioned just a few minutes ago, that there really Iraq on this matter systems, which demonstrate these and and in fact, there are a number of convents.

  • Matter systems, which are driven by loops of voter, sees, loops on off effectively of strings.

  • And there's a a particular thing called the Vine and Equation, which which is used a lot in helium.

  • And no one's really been able to derive that equation from first principles.

  • And I think there's a way of doing it from the work we did on.

  • So that was something I carried on working on and still am thinking about with Tom and Danny Steer, but basically the idea of using strings in cosmology.

  • Yeah, we stop thinking about that for a little while.

  • And it wasn't until about 2002 when I was, in fact, early 2003 I went to a meeting in Santa Barbara, one of the perks of working in this field, and when I was there I got chatting to a few people who who were thinking about a different type of string.

  • They were thinking about what we might call fundamental strings off the super strings of string theory.

  • Back in the 19 eighties, people were working on that.

  • And if that was probably the most brilliant theoretical physicist alive today, Ed Witten had had asked the obvious question, If you have cosmic strings and if you have these fundamental strings, maybe they're the same thing on he'd come to the conclusion that couldn't be basically on the fundamental string.

  • Turn out to be very unstable if you If so, if you formed a string that was, you know, the size of a galaxy than a fundamental string would just want to chop up incredibly quickly.

  • Um, he also discovered that if you if you looked at what the natural value waas for this mass of the fundamental string, it was where two big compared to what observations were telling you the cosmic string could be.

  • And so there were these reasons why you know, the instability, the fact that the masses didn't work out, which meant that the feeling was they wouldn't want to work.

  • But in the early nineties, there was kind of a string revolution.

  • A second string revolution in which it was realized there was a new class of objects could fall on these new class of objects.

  • In those new class of objects these strings could actually be stable.

  • Normal strings that the normal strings, which we thought were unstable, could be stable.

  • Oh, at least live way, way longer than the age of the universe, Andi, that they could have attention or a mass per unit length much lower than Witten had thought.

  • Andi opened up the possibility that actually, maybe these strings could be like the cosmic strings and what were they became known as cosmic superstrings.

  • And so I I was involved in some work looking at that.

  • And that was one of the papers which sort of rejuvenated the subject in that a lot of the string theory people began to get it excited, not least because they had some unusual properties.

  • These cosmic superstrings.

  • It could come in different flavors, so that now, when let's call it an orange flavor in a yellow flavor.

  • If they came together, they wouldn't simply pass through one another that they couldn't because they had their various colors and they couldn't simply chop and go on.

  • Dhe connect the orange with the yellow.

  • They'd have to form a composite in between.

  • So you ended up with the position where these strings would no longer form simple loops, but that form what you call junctions three way junctions so two strings would come in and they they hit each other.

  • And at the point whether it hits each other that have to be a new bridge would evolve out.

  • And so this lead to these more complicated networks, which I and others have big have been, have been analyzing and thinking about on We're and we're looking at the possibility that these objects could actually be seen no, both in the microwave background, but also, if you remember, I said, the primary decay root of strangers through gravitational waves.

  • These strings on cosmic strings have some wonderful properties on them.

  • For example, when you have a loop of string, I'm getting to the decay of the strings now on how we might find them.

  • So if you have a Lupus string that's oscillating and backwards and forwards, then every now and again, once in an isolation, usually it would be a part of this string, which forms what's known as a cusp.

  • This customer is a very kind of a sharp region, which goes at the speed of light instantaneously goes at the speed of light on because it so sharp it's got so much energy packed into this region, it can emit bursts of gravitational waves.

  • And so there are detectors out there.

  • There's the lie go detector, and then they're upgrading it to the advanced, like your detector, which l searching for these so that you would get these beaming events coming up from the strings on DA number of us have been working on the properties of these beaming events, and you started to see whether or not they could be detected by the gravitational wave detectors.

  • And it's one of the many things these gravitational wave detectors will be looking for.

  • Beams grant beams of gravity.

  • Yeah, shooting out from these objects on because they are so sharp they don't beam gravitational waves that can be mother things they can beam particles out.

  • So they're just It's just like the ultimate laser disc a bouffant on.

  • The neat thing is, it's not doing it all the time.

  • It's doing it once a cycle, you know, just go beaming beams and beams.

  • And so you have this sort of pulsing effect that you ca NBA gin to look for.

  • You It's a distinctive signature.

  • So you have those and then you have other features on these strings, which are called kinks.

  • So every time a string chops chops off chops a loop off, it leaves this discontinuity where one string has come in on me and it's met.

  • The other string on where they've met on a Lupus has gone off.

  • You're left with this sort of discontinuity.

  • The string one string here and the other string there on that, then begins to propagate around the configuration.

  • And you just get buildup of these kinks, which also read yet on DSO.

  • You get these extra beaming effects from these objects as well, just making eyes just great, isn't it?

  • So one of the things they're trying to do is understand the distribution of these things and then the amount of radiation, the rate at which they'll come off.

  • And of course, we're not seen it.

  • Things could get a bit that's totally made out.

  • But one way of interpreting something that you don't see isn't that the objects, not there, is telling you about what that mass scale can be.

  • You know, if it's just getting lower and lower and lower.

  • If the mass scale of the strings was high enough, the tension in the strings was hide off the beam more energetically on, we would have seen them, So the fact we haven't seen them?

  • One interpretation is the mass scale is dropping down on that is so, in fact, they're dropping down so that they're getting difficult to reconcile with.

  • Grand Unified Fair is the typical grand unified there is.

  • But then they are consistent with some of these cosmic superstring models that those air still perfectly plausible.

  • If the coast what were background isn't helping the cause of the moment, it isn't matching.

  • There's no finding these gravity lasers, the big planes.

  • You know, finding any of the evidence and invest some of the evidence is going against the only what makes you keep the faith well from the first thing is it's such a beautiful idea.

  • The idea of a first transition is well accepted in in particle physics.

  • On dhe, the Higgs mechanism is a phase transition on dhe.

  • The breaking of a symmetry, which is what is going on here, is well accepted.

  • And so the the fact that these objects were seen in equivalent systems.

  • Terrestrial systems is sort of evidence that the ideas work.

  • Now there's no reason why that I'm aware of that.

  • This shouldn't be allowed to happen in the early universe, but we don't know if it did happen.

  • We know first transitions happened that we believe that they occurred, whether or not they're Kurds in such a way that they produced these objects.

  • And there are two more three more types of defects.

  • By that, I should just give them a name check, which isn't munna polls, domain walls and textures.

  • These could have all formed.

  • And in fact, the multiples is one of the reasons why people came up with the idea of inflation, which will maybe touched on in a different video.

  • That is the fact I think that these things are so, so natural in the sense of fair transitions are expected to have played a major role in the universe early universe that makes me think we should be looking for them and the fact that we don't see them yet.

  • I still interpret as more of a bound on the strings rather than this is clearly evidence this didn't have it may not have happened, and eventually, when it becomes clear that the detectors just have no chance of seeing these objects, then I think it's time probably to move on.

  • But that's not at that stage.

  • And in fact, Plank is currently looking at its second year of data on one of the things that it will be looking for.

  • What is known as polarization effect.

  • That's where the the radiation emitted gets polarized by the presence of objects and cosmic strings conduce that it can polarize the light.

  • And so and there are things called B modes, which is a particular type of polarized light to do with magnetic fields that cosmic strings will put, they'll produce a particular signal.

  • And that's something that I'm working on with regard to both cosmic strings and cosmic superstrings, with people here in Nottingham trying to make a prediction of what that signal should be, so that we can see if it's there in the plank, debtor or not probably won't be, but you never know how scenes where there's a 1,000,000 of them in the room or they like these great ribbons in states that you would want to cut through.

  • So that's a really important question.

  • And so the long strings that there are two types, right?

  • There's that There's the strings which stretched across the observable universe.

  • There will be a border, a dozen, maybe 2030 that kind of figure for the density of them on.

  • But the but the loops of string.

  • There are billions.

  • There are billions.

  • In fact, the majority of the energy in the strings are in loops because these long strings chopped themselves up into into loops.

  • These loops then gradually decay.

  • But the majority of loops that are formed a chopped off around the size of the observable universe at that time.

  • And then So they take a long time to decay, and they're being chopped off all the time.

  • So you've constantly replenishing these loops.

  • They'll bill the whole group will have decayed, but there'll be a whole group still decaying, and then a new group beginning where the new ones being chopped up from from the big giant 30.

  • Yeah, from that from from those and then from the big loops themselves, which is chopping themselves up on Dhe from all of it, you know, all the other loops will be chopping themselves up all the time.

  • It's not a case of it is not the majority of the loops ourself intersecting, in other words, that as they evolve they'll they'll move in such a way.

  • So if this is a loop, it will.

  • It will move in.

  • Such a weather, at some point in its evolution, it will chop off will come to more loops on dhe.

  • Most loops do that.

  • There's a small subclass of them, which called non self intersecting, which are able to evolve so as not to chopped themselves up on.

  • Some have come back out again and then go back and come back out without without some breaking up.

  • In fact, in the early this, this is research in This is how research girls that when when strings were first thought of a serious candidates for structures, one of the nicest results that someone came up with.

  • In fact, a guy called Neil Cheer up came up with Waas.

  • He looked at the class of non self intersecting loops and he realized that they're kind of could could match the distribution of clusters of Galaxies, and he got this kind of nice one toe, one map between the distribution of these big loops and the distribution of clusters.

  • And that was a very exciting time because people thought, Oh, wow, these you've clearly got evidence here of this.

  • But then we began to realize that actually, the string dynamics worked.

  • It didn't work quite like that.

  • And that that was a kind of a fluke on Dad.

  • Actually, the majority of the loops don't do about the toll.

  • It is break up very rapidly.

  • Encounter one of these strings, especially one of these big 30 that you've got me in your dream.