Cosmic Superstrings - Sixty Symbols

those of you who follow us on Twitter or Facebook might know that our very own professor Edie 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 bowtie something you don't see every day professor Edmund Copeland of the University here at sixty symbols of course were especially happy for professor Copeland now his win has nothing at all to do with sixty symbols he's won it for his own research into three areas cosmic strings and super strings inflation that's not the financial type of course we're talking on a cosmic scale here and dark energy so we're going to post three videos one on each area of research and I really let ed off the leash a bit here so it's going to 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 here you go here's the first of three videos with Ed and this one is cosmic strings and super strings you know when they announced the Nobel Prize and they announced it to Higgs a non-glare who quite rightly received the prize and they didn't give it to kibble which upset me partly because Tom's 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-glare fully deserved by feel sorry for Tom and what we now need to do is go and find cosmic strings so he can get his own Nobel Prize because Tom kibble came up with the idea of cosmic strings back in 1976 these wonderful objects first of all you need a real imagination to come up with these kind of things they're related to the Higgs field they're they are made up of what we could call the Higgs field but just at a completely different energy so cosmic strings are examples of something called a topological 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 and they're incredible they're amazing objects and so I'll just try and describe give you an idea of them there their strength their thickness is much much smaller than a proton okay so you've no chance of seeing them but there can be as 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 there the mass of the object so the energy stored and the objects would be of a kilometer of them would be about that of the earth and they could they formed and these particular ones would have formed within the first ten to the minus 35 seconds after the Big Bang you just need quite an imagination to think about these things and they formed in the first transitions just as we've been hearing about the Higgs field undergoes phase 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 phase transition throughout the universe this doesn't happen all smoothly and there are various parts of the universe where it were a bit of the original high energy bit gets trapped and these are formed the lines these long strings so that the strings of the original high energy bit that was before the phase transition and they're surrounded by the new phase which is at a lower energy and once they're formed you haven't you have a network of these long strings crossing across the universe and loops of string and then they're 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 to 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 shoelace okay imagine a shoelace and you as it wraps back and crosses itself well with a shoelace 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 kilometer is about the mass of the earth there are oscillating around they're moving closer they have you know a good fraction of the speed of light and because they're moving and oscillating they radiate they radiates gravitational waves just like any massive object that moves will radiate gravitational waves and that's its principal way of losing energy because the if they didn't do that what would happen is the long strings would just keep stretching as the universe expands this be like pulling an elastic band and 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've not seen any so that either they're not there or something else has happened which is meant they don't dominate and the thing that we think happens is that because these long strings can form loops and these loops can then radiate their energy in 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 in the strings doesn't disappear it doesn't grow and become too big just becomes like the Goldilocks amount of energies just right and that was what got people very excited when Tom kibble first came up with this amazing idea of the formation of these objects he demonstrated that when they evolved under the expansion of the universe that they would chop off these loops and they would radiate away their energies in just the right amounts so that they over all any 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 and it and you find it for for phase transitions which correspond to what we call the grand unified phase transition that's where we unify the strong the electroweak and the electromagnetic forces this is at 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 produces the cosmic microwave background radiation and the distribution of galaxies this was what that it seemed to be the case back in the 1970s and early 1980s that cosmic strings provided that the seeds from which structures would fall so people so now 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 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 and all different sizes across the across the 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 cosmic and it was found that cosmic strings just weren't working they were not matching the observed Cosmic Microwave Background anisotropies and so people began to lose interest these wonderful objects that could well afford in the early universe and I should say that the analog objects that have been observed in condensed matter systems they are observed in liquid helium systems they're observed in systems and pneumatic liquid crystals the scaling properties are all seen and match what you might expect from cosmology is that they're not been seen yet in cosmology so back in the at the turn of the at the end of the 1990s beginning of 2000s people began to lose interest in 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 as 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 peak and and not the secondary Peaks not the secondary Doppler Peaks I carried on because I was interested in some other features and there are some as I mentioned just a few minutes ago they're real Dirac on this matter systems which demonstrate these and and in fact there are a number of condensed matter systems which are driven by loops of vortices loops and effectively of strings and there's 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 and so that was something I carried on working on and still am thinking about with Tom and Danny steer and but basically the idea of using strings in cosmology yeah we stopped 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 were thinking about a different type of string they were thinking about what we might call fundamental strings or the super strings of string theory back in the 1980s people were working on that and if I were probably the most brilliant theoretical physicist alive today Ed Witten had asked the obvious question if you have cosmic strings and if you have these fundamental strings maybe they're the same thing and he'd come to the conclusion they couldn't be basically and the fundamental string turned out to be very unstable if you if so if you formed a string that was you know the size of a galaxy then a fundamental string we just want to chop up incredibly quickly he also discovered that if you if you looked at what the natural value was for this mass of the fundamental string it was way too 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 the feeling was the one of them to work but in the early nineties there was a kind of a string revolution a second string revolution in which it was realized there was a new class of objects could fall and these new class of objects in those new class of objects these strings could actually be stable these are the the easiest cosmic strings or long strings normal strings that the normal strings which we thought were unstable could be stable or at least live we're way longer than the age of the universe and that they could have a tension or a mass per unit length much lower than Witten had thought and it opened up the possibility that actually maybe these strings could be like the cosmic strings and what we and they became known as cosmic super strings 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 super strings it they could come in different flavors so that now when let's call it a an orange flavor in a yellow flavor if they came together they wouldn't simply pass through one another they couldn't because they they had their various colors and they couldn't simply chop and go and connect the orange with the yellow they'd have to form a composite in between so you you ended up with the position where these strings would no longer form simple loops but they'd form what you call junctions three-way junctions so two strings would come in and they they'd hit each other and at the point where they'd hit each other that have to be a new bridge would evolve out and so this led to these more complicated networks which I and others are bigger have been have been analyzing and thinking about and we're and we're looking at the possibility that these objects could actually be seen not both in the microwave background but also if you remember I said the primary decay root of strings is through gravitational waves these strings and cosmic strings have some wonderful properties on them for example when you have a loop of string and I'm getting to the decay of the strings now and how we might find them so if you have a loop of string that's oscillating and backwards and forwards then every now and again once in an oscillation usually it would there'll be a part of the string which forms what's known as a cusp this cusp is a very kind of a sharp region which goes at the speed of light instantaneously goes at the speed of light and because it's 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 LIGO detector and then they're upgrading it to the advanced LIGO detector which I'll searching for these so these you would get these beaming events coming out from the strings and a number of us have been working on the properties of these beaming events and you know so that to see whether or not they could be detected by the these gravitational wave detectors and it's one of the main things these gravitational wave detectors will be looking for beams of gravity beams and gravity you know shooting out from these objects and they because they're there's there they are so sharp but they don't just beam gravitational waves they can beam other things they can beam particles out and so they're just it's just like the ultimate laser this could Buffon it and that the neat thing is it's not doing it all the time it's is doing it once a cycle you know it just goes beaming and beams and beams and so you have this sort of pulsing effect that you can begin to look for 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 and chops a loop off it leaves this discontinuity where one string has come in and it's met the other string and where they've met and loop has has gone off you're left with this sort of discontinuity the string one string here and the other string there and that then begins to propagate around the configuration and you just get a buildup of these kinks which also radiates and so you get these extra beaming effects from these objects as well just making history it's just great isn't it so one of the things you'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 this could be the bit that's totally made up 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 the 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 high enough they'd beam more energetically and we would have seen them so the fact we haven't seen them one interpretation is the mass scale is dropping down and that is so in fact they're dropping down so that they're getting difficult to reconcile with grand unified theories the typical grand unified theories but then they are consistent with some of these cosmic super string models those are still perfectly plausible if the Cosmic Microwave Background isn't helping the cause at the moment it isn't matching they're not finding these gravity lasers these big waves you're not finding any of the evidence and in fact some of the evidence is going against the only ER 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 particle physics and the Higgs mechanism is a phase transition and and and the breaking of a symmetry which is what is going on here is is well accepted and and so the the fact that these objects are seen in equivalent system terrestrial systems is sort of evidence that the 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 phase transitions happened we believe they're they occurred whether or not they occurred in such a way that they produce these objects and there are two more three more types of defects by the way I should just give them a name check which is monopoles domain walls and textures these could have all formed and in fact the monopoles is one of the reasons why people came up with the idea of inflation and which will maybe touch on in a different video so that it's the fact I think that these things are so so natural in the sense of fair strands Asians are expected to play 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 now this is clearly evidence system now 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 to move on but that's not at that stage yet and in fact planck is currently looking at its second year of data and one of the things that it will be looking for and what is known as polarization effect that's whether the radiation emitted gets polarized by the presence of objects and cosmic strings can do 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 super strings and with people here at Nottingham trying to make a prediction of what that signal should be so that we can see if it's there in the Planck data or not it probably won't be but you never know how fountains are they those scenes where there's a million of them in the room or there are they like these great ribbons in space that you wouldn't want to cut through because I'm so that's a really important question and and so the long strings that there are two types right there's that there's the strings which stretch across the observable universe there will be of order dozen maybe 2030 that kind of figure for the density of them and but they 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 chop themselves up into inter loops these loops then gradually decay but the majority of loops that are formed a chopped off you know 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 a whole group will have decayed but there'll be a whole group still decaying and then a new group beginning and where the new ones being chopped off from from the leaf yeah from that from from those and then from the big loops themselves which are chopping themselves up and 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 it's not the majority of the loops are self intersecting in other words they as they evolve they'll they'll move in such a way so if this is a loop and it will it will move in such a weather at some point in its evolution it will chop and off will come two more loops and most of the loops do that there's a small subclass of them which are called non self intersecting which are able to evolve so as not to chop themselves up and somehow 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 goes it when when strings were first thought of as serious candidates for structures one of the nicest results that someone came up with in fact a guy called Neil Turok came up with was he looked at the class of non self intersecting loops and he he realized that they're kind of could could match the distribution of clusters of galaxies and he got this kind of nice one-to-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 this string dynamics worked didn't work quite like that and that that was a kind of a fluke and actually the majority of the loops don't do about at all they just break up very rapidly if I was to encounter one of those strings especially one of these big 30 that you've got me drape I what would happen I was think about that today and it wouldn't be a great idea I think is a fair thing to say because one of them one of the things that strings have they're so massive so they've got this large string tension and if they're moving they will they affect matter moving around it in fact if you were to walk around a straight string then you might think you go from 0 degrees you walk all the way around and you come back to 360 degrees with a straight string that's not quite right the string sort of cuts out a bit of space so when you walk around it makes your space conical and so walking around a string you might walk around maybe 350 degrees and you've come back to where you started and what that effectively means is that trajectories of objects going past a string get bent so this is one of the ways people think about looking for us looking for strings you you looked and coming to answer your question by the way you get light coming by the strings and will get bent and then when you trace back that light it looks like you've got double images and in fact one of the distinctive signatures of strings would be not that you get a pair of double images because that happens all the time but actually you'd get a line of them because the string is a line object and so if you if you're lucky you'll get lots of these lensing and there have been attempts to find such consecutive lens de vents and they've been found but they've turned out not to be from strings but just to be pure chance so these things are so massive right and so matter when it goes by it gets gets perturbed it gets then and that's why people thought that's its scientific word shove ik shoved in that's why people thought strings would be very good for structures because they knew that as a string went past say a distribution of matter search would be the gravitational pull around the string that the matter would clump together and then you've got your initial seeds that you've got your initial fluctuations which would allow other matter to form around it and you get wakes what I think will happen is so when one of if one of these strings was to say go through the earth which is alight you're going through you and what it because it's you know you're not going to see it first of all because it's so infant this incontestably thing it's about where I think it's about a trillion times smaller than the size of a hydrogen atom so it will go straight through but it's going through about point three or four the speed of light is going through police going straight through but it will do this effect right that it the matter the dense material that the earth is made of will get shoved in its also get attracted behind the string as a string as if it's performing a wake behind it and the argument is that I was and I was looking at the calculations that what will actually happen and in fact they're using this to akai and say maybe some of the earthquakes on the earth is due to this okay this is the kind of imagination you need so the string goes through the dense matter that's making up the earth gets attracted in behind the string so and then it begins to bounce it gets oscillates like this and they're saying it could be could cause these the ripples that you see a surface waves that lead to earthquakes for you and I it would probably have a bit more maybe what I can't figure out is whether I know it's going to sort terra's apart or whether we're just going to sort of feel you know pretty unpleasant for a few minutes and then we carry on yeah I do a bit obsessive bits I really yeah in my head I I happily will and think about them evolving chopping up bells happily think about how they might form my test for them I spend a lot of time trying to because they're fantastic right if they're there either as cosmic strings or as cosmic super strings I mean you have a probe a unique probe of the very earliest moments of the universe that we just can't get to without this kind of thing so I think the goal at the end of its worth it and the the theory behind it is so beautiful I mean what I don't know how kibble did it I mean he's he is one hell of a guy he just he comes up with a Higgs mechanism and then he just thinks I will now move on and I'll just discover topological defects it it it's just remarkable that he was able to do this and and they they have driven so much research the whole idea of these defects and and if we do see them then it really will be an amazing result for the understanding the early universe I think I'd be disappointed if we don't see them but I you know something at the end of the world and if they're not there and it's it's you know there's no evidence for them and yeah I'm very happy to think about them and work on them I'll feel I've done some really fun stuff just trying to understand objects that had every right to be there there was no reason why they shouldn't be there in the sense of the dynamics with which we think of them forming the the process which we think of Informer makes complete sense it's just that the the particulars of by which they would have formed didn't happen that's just unlucky and and yet the mathematics that we've developed that in understanding them and and the the physical intuition we've we've developed I think will has probably played a role in other things that I've been working on and other people have been working on know I'm if they're not there they're not there and I'm not going to loose like the very first thing I worked on this from my PhD were called Colusa klein theories I worked on a subject or candy Ellis Weinberg which everyone got very excited about as being a way of unifying the forces and it didn't work so maybe people should take note of what I'm working on and then move up to something else quickly just to reminder those other two interviews with Ed about inflation and dark energy will be coming very soon and congratulations again on the medal brilliant

Channel: Sixty Symbols

Views: 721,637

Rating: 4.9357905 out of 5

Keywords: sixtysymbols, Superstring Theory, edmund copeland, particle physics, Particle Physics (Field Of Study), big bang

Id: 03vIkZR2hNY

Length: 28min 41sec (1721 seconds)

Published: Fri Nov 29 2013

Reddit Comments

[u/loooooooooooo]

The editing on this was uncharacteristically annoying for a Brady Haran video. Had to switch to just listening to the audio because it was so distracting.

[u/iashido]

Inflation... the cosmic scale :)