13:01:58 Okay, I think we're good to go. We have a room full of visitors and we have our speaker here ready to go. My name is Lisa Stewart, and I am Chief Administrative Officer at the Kavli Institute for theoretical physics and Santa Barbara, it is my honor
13:02:16 today to welcome you to the seventh in a series of talks, NSBP's innovate seminar series, and today our speaker is Morgane Konig close to that.
13:02:36 I am not French native speaker so I tried.
13:02:41 And this is a speaker series, presented by the National Society of Black physicist, and our speaker today comes to us from UC Davis,
13:02:52 today's talk will be approximately 30 minutes and presented in webinar format.
13:02:58 This means that we will hold questions until the end. So as you have questions throughout the talk, please type them in the q amp a section, and our speaker will try to address these questions at the end, as time permits.
13:03:11 Next up my.
13:03:13 It's my pleasure to introduce you to Farrah Simpson, who is the leader of NSP Student Council, which is also the group responsible for leading this innovate seminar series, thank you again for joining us and we hope you enjoyed today's talk.
13:03:29 Hello everyone and welcome back to the MSP innovate seminar series, and thank you so much for joining us in this seminar series is a new forum for members to share their research ideas and projects in a non specialist way with a wide audience as Lisa
13:03:48 said it's a 15 minute talk, called 15 minutes of question and answer, and it was curated by the student council for or members, the new children's research and we're very excited that this is our seventh talk.
13:04:01 And we hope that you continue to join and support or series, and I would now like to introduce the President of the National Society of Black business Dr.
13:04:09 Alexander.
13:04:15 Thank you Lisa and Farrah. It's great to be here, and we're very excited about this.
13:04:22 Our next speaker. Morgan, soon to be Dr. Morgane Konig hails from Paris, France.
13:04:30 She is part of our, you know, NSBP family, and this VIP member, and she did her undergraduate studies, both undergraduate and master's degree in mathematics and physics at in Paris and then move to UC Davis where she's finished up a PhD dissertation under
13:04:51 the supervision of a colleague of mine, great cosmologists Nemanja caliper Morgan's actually been also co leading a group of of brilliant young black theorists, including our own Delilah gates and others, and a week on weekly meeting called Nexus where
13:05:12 they engage and talk about do lots of calculations together. So anyway, I'm not in a nutshell is.
13:05:25 So all yours.
13:05:27 Thank you for the lovely introduction and thank you for having me.
13:05:54 Okay, so today I'm going to tell you about inflation and a particular model of inflation called hybrid monogamy, and this is based on the work that I did with my advisor and Amanda caliper and a postdoc James Clark.
13:06:11 So today I'm really going to try to motivate inflation, why do we need inflation and then what do we need to build a model of inflation.
13:06:20 And then in the third part I'm going to try to explain to you why this hybrid model of inflation solves a lot of our problem, and it's a good solution for inflation.
13:06:32 Okay, first of all what is inflation or should we say, when is inflation. Inflation is a moment in the expansion of the universe in the history of the universe that last from 10 to the negative 36 second to tend to the negative 33 seconds.
13:06:49 And during that very short amount of time. The universe is going to expand by a factor of 10 to the 26 so at this time the universe is very young, it's very dense, and it's going to expand extremely fast to give you an idea, the expansion during inflation
13:07:07 is as much as between the no inflation, up to today.
13:07:13 So this model of inflation. Inflation as an age of expansion has been developed, mainly by three. Brilliant physicists, Alan growth and Melinda and
13:07:27 or just a little technical issues.
13:07:35 here. And sorry and Andres trimming.
13:07:38 So okay first of all, why do we need inflation, why did this physicist need to come up with this idea of an extremely fast, inflation, an extremely fast expansion of the universe.
13:07:52 So we really came from observation so here we're looking at the oldest map of the University School of the CMT the cosmic microwave background. And this is a stage of the universe at 380,000 years after the big bank.
13:08:09 So we're going to this stage the universe is still very young, but photons are free to propagate and the bigot, all the way to us, and this gives us a lot of information so what are we looking at we're looking at difference in temperature so the hotspot
13:08:26 or the red one the blue spot with cold one.
13:08:29 But overall it's extremely uniform to 2.7, Kelvin, with very with hotspot and the cold spot there again very, very close in temperature. And the reason why this is surprising is because it's extremely uniform.
13:08:46 To give you an example, if you have a soup and you put in the microwave and you warm it up your soup is not going to be the same temperature everywhere, but the microwave background assembly is basically the same temperature everywhere.
13:08:58 And so looking at that map we can also evaluate the power spectrum, and that gives us a lot of infer information about the cosmology we can get information about the density of photons, at the edge of the universe etc etc so we get a really a lot of information
13:09:17 Another thing that's important about this map is that older is extremely uniform. We don't want it to be absolutely uniform because those codes, but in hotspot those difference in temperature those difference in density or the seeds for the structure
13:09:33 that we see today.
13:09:36 Okay, so what do we know about the universe we know the universe is very old 13.8 billion years old, it's very homogeneous. It's almost perfectly flat and it's made of older good things to mate of galaxies etc etc.
13:09:49 And it looks like it's filled with those very small structure that we're seeing the CFPB that again, are the seeds for the large scale structure that we see in the universe, today and that rose.
13:10:03 A couple of questions. First of all, why is the universal flat.
13:10:07 Why is the universe so homogeneous it's called the horizon problem, what are the origin of the structure, what are the seeds that are going to evolve and give us the galaxy that we see today or, or, mainly the main question is, how do we were produced
13:10:23 this observation from arbitrary initial conditions.
13:10:29 observation from arbitrary initial conditions. Okay, so let's look at some of those problems the whole reason problem the tourism problem is the problem that, again, we have the same temperature everywhere.
13:10:37 So if we look at those two points A and be there very far away, and what is interesting is that with the old model of this big bang. And if you look at the past like cone of those two points on the right here.
13:10:53 It appears that those two points were never in causal contact the two orange triangle, never meet there is no common area. And so those two points were never able to exchange information.
13:11:08 But then if they were never able to extend information, how come that they have the same temperature.
13:11:13 Another way to think about it, is to look at the Hubble sphere. If you're inside of Hubble sphere of two points there is no Hubble's fear they're able to communicate they're able to exchange information, but here the Hubble sphere with the old model of
13:11:27 the Big Bang. The Hubble sphere radius is extremely small. So again, those two point DNQ are never look like, what they were never able to exchange, any type of information.
13:11:38 So how do we explain the fact that they have the same temperature.
13:11:41 We can also evaluate the number of causally disconnected bridging bridging they're not able to communicate and we find that this number spent the night we have tend to the nine causally disconnected region.
13:11:57 Okay. Another problem is the flooding this problem. The universe is flat and one way to evaluate this is to look at this omega, that's the actual mass density over the critical mass entity anyways know today that it's roughly one.
13:12:14 But in order for this to be one today, it would have had to be one to the tend to the negative 16 you would have to be exactly one earlier in the universe and this is also something that we don't really know we didn't really know how to explain.
13:12:29 So now let's see how inflation solves those problem, so you can hear remember we have that problem to two points with those orange regions that we're not in causal contact.
13:12:40 But what if we're able to think about a mechanic that would push the beginning of the universe. Earlier in time, we do this, then those two points would be able to be in constant contact earlier than the universe is going to expand, very quickly, and
13:12:56 they're going to get out of our contact, but still keep some information, and hence have the same temperature.
13:13:05 We can also express that looking at the Hubble sphere. So again, if two points are within the Hubble sphere, they can communicate so if we think about a decreasing Hubble sphere from earlier in the universe, all the way to this end, we can see that those
13:13:19 two points. Not only were in causal contact, but this region was able to exchange information that to the left you can see an expression of a decreasing Hubble's fear DTDTH minus one is the Hubble sphere.
13:13:32 And so a is a scale factory tells you how the universe expand and he is the Hubble perimeter.
13:13:39 And by doing a little bit of calculation we realize that if we need a decreasing Hubble's fear it's equivalent to having an accelerated expansion, a double that is positive and that's why when we talk about inflation we talk about an area of accelerated
13:13:55 expansion.
13:13:56 Okay so inflation, which is again a moment, an area of an era of accelerated expansion so for the horizon problem now, does it solve the flatness problem.
13:14:07 So we can rephrase the flatness problem, looking at this omega parameter and remember we need this omega parameter to be basically one earlier.
13:14:18 In time, and one which again to solve that is to have a decreasing Hubble's fear we need ah to be very large so that omega minus one will be very small.
13:14:27 And so a decreasing Hubble's fear solves that problem and remember that is the same statement as saying that we need an accelerated expansion. So, inflation.
13:14:39 so suppose the horizon problem.
13:14:41 And the flatness problem, and inflation to have inflation we need a decreasing her Hubble's fear, which is the same thing as saying we need an accelerated expansion.
13:14:50 And if we want to feel the universe with a particular fluid, we need a fluid that satisfied the following set parameter is W smaller than negative one third.
13:15:01 Okay, so now how do we build a model of inflation, because we have no preferred direction. First thing to think about is to look at a scalar field. So this is the action of a scalar field when we have gravity, it's dynamical we have a potential, and we
13:15:16 we can look at the equation emotion where we have a friction term is the term on the right, and a restoring force. So now we talk about slow roll inflation because we can define two parameters, excellent and a tiny those two parameters are small enough,
13:15:32 we know that we can have inflation that less long enough to give us what we see today, in the universe, so excellent here is going to be a measure of how flat, the potential is and it has going to be a measure of how long it stays flat.
13:15:48 So we do want a potential but we also want some quantum fluctuation because this quantum fluctuation give us the seed for the structure formation.
13:15:58 So we do need quantum fluctuation in order to have those little different intensity that gives us again the Lord structure that we see today. But if we have quantum fluctuation.
13:16:15 This can spoil our potential so we need to be able to control those quantum fluctuation.
13:16:23 Because here we can just evaluate how dangerous, those would be, and so on the first on the on the left part, we look at how the inflate on interacts with itself so inflate don't is going to have to couple to other particles because at the end of inflation.
13:16:35 Inflation is going to oscillate and give us the particle from the standard model. So we can first look at the self introduction of the inflation.
13:16:44 But if we look at it, we realize that we get a correction in log. So those corrections are actually controlled. We can also look at how the coupling between the inflation and gravity is going to affect our theory, and those quantum corrections have been
13:17:01 calculated. And if we make sure that the potential is flight and implement, make sure that the potential is flat for long enough, it doesn't seem to be a problem, either.
13:17:11 So, again, it looks like. One way to solve those issues, is to have a potential that is flood, and that is flood for long enough, and one would you have that is, with a shift symmetry forever shifts symmetry, we have a flood potential.
13:17:26 So we want it to be flood, but not forever.
13:17:29 Because we keep this idea of we want something to be flooded let's just look at a particular model of inflation just easier model we can think about, we have dynamical field, we're going to give it a mass.
13:17:42 So that's give us this potential. Here we want to evaluate this low roll parameter and remember if those parameters are small enough, we have a good theory of inflation.
13:17:53 But in order for this parameters to be small, we need to start with field with a value that would be above the Planck scale, the Planck scale is the the scale of which we are in the quantum gravity wrong.
13:18:09 So here we need to start with a field into quantum gravity Roman that can be a problem because then we have to control the correction coming from quantum gravity.
13:18:19 OK, so again, we need again we need the potential to be flat we need to be fluent enough we need, what we call the shift symmetry symmetry gives us a lot of potential for this is an equation that maybe is a little complicated there's an action we have
13:18:39 we have a dynamic field, and we have this for form. But in a nutshell, we have here, shifts mature but in a nutshell, if you look at the dynamic of this action.
13:18:55 It just end up being a theory of a massive scalar field with a shift symmetry. But here, if you look at the last equation.
13:18:58 At the bottom we have this qq here is a constant that we can choose.
13:19:03 And every time we choose a constant would jump from one possible potential to the other one. And that is why it's called monogamy monitoring means choosing a path.
13:19:12 So here what we do is we are going to choose a value of two we're going to choose a particular path and we're going to realize what we called a monogamy.
13:19:22 I guess in the model that we did, we looked at monogamy because remember he has a shift symmetry which ensure that the potential is flat and it's flat enough.
13:19:30 So once we have our model, we also need to make sure that it fits the data we need to make sure that it gives us the cosmological parameter that we want.
13:19:37 And one of the great thing about our model is that it keeps the field set plank in that way we don't have to worry about the quantum gravity corrections.
13:19:46 So this is the model, and instead of one field, we have to field, we have sigma and fine. So fight here is still in fleet done and see my school, the water fall.
13:19:58 The waterfall fail so what's going to happen is sigma is very quickly going to reach its minimum, and then we're going to effectively end up with a theory with only one field.
13:20:09 So that idea came from Linda, who developed.
13:20:14 Sorry, that who developed the method that is in green here.
13:20:18 Fine.
13:20:20 But the issue with this theory is that it does not give us a good spectral index, the spectral index tells us how our theory is scaling variant, and we know that it has to be around point, 96, but his model gift something that was greater than the ones
13:20:38 that did not fit the data.
13:20:41 did not fit the data. Now Stewart came up with a different model was still have the coupling it's a little bit different with change the convexity of the potential, and this time we get correct cosmological perimeter.
13:20:53 But the problem is you look at it is that phi does not have a mass, and we do not have a symmetry sZ to symmetry, so we thought, Okay, how can we get the both the best of both worlds.
13:21:07 While we can just add them up together, make sure that inflation is in the steward regime for long enough to give us the good cosmological parameters and that that the end, it's going to be in the Linda's regime.
13:21:21 So again here even though it looks complicated it's always the same story. We have sigma being the waterfall field that is going to reach its minimum really quickly, with a certain value on the right, and then we're going to end up with an effective potential
13:21:36 that is only going to depend on five fi is going to be the only dynamical field.
13:21:41 And then here we had to do is, is make sure that we had two good values for our apartments or parameters here, and began Linda, we need to find good parameters that would ensure that we are in the steward regime long enough, and that we end up in the
13:21:57 Linda's region.
13:21:59 So we looked at the data and we look at three particular cosmological parameters the spectral index that I talked about earlier the scalar fluctuation that's around 10 to the negative five, and the ratio of gravitational waves to density perturbation
13:22:12 that also need to be small.
13:22:16 And we were able to evaluate those values here and as r amp d rho v zero.
13:22:25 And we're able to keep our field sub plank and so here we showed that actually, although Linda's model didn't work, or able to resuscitate that model of monitoring was to field, and to keep the field sub plank into we did not have to worry about quantum
13:22:42 gravity corrections. We also had to make sure that our theory was stable against quantum corrections. And to do that we purchase the background and we look at one look effect to make sure that the mass corrections would not boil, or theory and hearing
13:22:59 read this is the only one that we had to worry about but they looking at them and comparing it with the previous values for our parameters we actually realized that that was also controlled.
13:23:10 So we can now why are we worrying so much about monogamy Why do we need to feel so the reason why monogamy is favored is because monogamy can be derived from a string theory from a higher dimensional theory.
13:23:26 And so in that way it has what we call the UV completion, or another word, we have an argument of naturalness this theory can be derived again from a theory in with a UV condition.
13:23:39 And so here we also had to do is we had to write this theory in complicated form so again we started with this theory of two scalar, but we need to show that we can write it in terms of those four forms because when we're writing this for forms, we have
13:23:54 a better argument to say that it can be derived from a string theory, and we were able to do it. So now again we have a theory of two scalar, that is stable against quantum correction that gives us the correct cosmological parameters that stays sub planking
13:24:09 so we don't have to worry about the quantum gravity corrections.
13:24:17 And so, this is I think a great way to think about inflation, because again this is a natural theory that comes from a high dimensional string theory that has a UV completion, that is stable that give us all that we want that fits the data.
13:24:40 that is protected from quantum correction. So now what we're doing it to do is that, so we realize that the the dual at week coupling we have to do it at strong coupling.
13:24:49 We know that it can be derived from a string theory but we still have to really like show it to all the mechanics.
13:24:57 And then there's a lot of different avenues that we can think about it at the end of inflation what happens, the inflation is going to oscillate is going to give us all the particles from the standard model.
13:25:06 This is called reheating so we can also see how does our model.
13:25:21 Behave during reheating, and another ways here we looked at two field inflation, but we could also look at three field inflation for field inflation, what can we learn from those models, is it more stable.
13:25:24 Do we get better.
13:25:26 A better mechanism we can also look into this avenue. Why, because again, string theory favors multi field, inflation. So, this is another avenue that we could explore.
13:25:37 All right, thank you very much.
13:25:45 Thank you so much more gun, I was very much looking forward to this talk and you did not disappoint.
13:25:52 Some comments wonderful um so if you have a question Could you just put your question in the q amp a box and then I'll moderate questions and answers.
13:26:16 Okay, so or first question is from the renowned cosmologist doctor and Shonda Prescott Weinstein, thank you for attending.
13:26:35 So the way I understand naturalness maybe it's just kind of a buzzword or it's the fact that we have a theory that is UV completed a theory that comes from a string theory because when you look at models of inflation, you can kind of come up with any
13:26:51 effective your theory look at the cosmological parameters and say okay this is also possible.
13:26:57 But one way to kind of discriminate between those different models and justify the use of a particular effective your theory is to say yes it can be derived from a string theory has a UV completion and I think that's what I mean want to talk about natural.
13:27:14 Thank you.
13:27:17 Um, we have time for just a few more questions.
13:27:24 You have any
13:27:29 or everything was so clear that everyone understands everything.
13:27:33 Okay, so we have another question. How does axiom under monogamy fit within the swampland criteria.
13:27:43 I'm not sure what you mean by the swim blend criteria, what would the way I understand this fun one again this this idea that there are a lot of different possible theories for inflation.
13:27:54 How does this one is his favorite compared to the other one is again because the x Sean.
13:28:02 This theory comes can be derived again from a string theory I mean you have ACCION in models of string theory. And so that way it would be, again, natural to end up with an effective feel three that would that would involve an accent I'm not sure I'm
13:28:20 answering your question, but yeah this is how I understood it.
13:28:25 Yes, if you have any follow up questions please feel free to put that in the chat, and we have another question. If there is. Oh, sorry. Have you thought about preheating in this model.
13:28:38 No, we haven't. We haven't and this is something that I would be very interested to to explore because I mean as you see we have really we kind of put two models together we have the Stewart version we have the Linda regime that is going to terminate
13:28:49 the end and that is at the end of inflation or waterfall field is not going to be in its minimum anymore and it's going to start being dynamical and that is I think extremely interesting to see how it's going to add and how it's going to give rise to
13:29:04 the, the particles from the centered models so I haven't had time to do it but it's something that would be very interesting to do. Yes, yes.
13:29:15 I'm far actually want to make a quick comment, can you hear me. Yes we can hear you. Yeah, actually Professor Weinstein's question is on point right on point.
13:29:23 So, in the context where the arm with this ACCION feel and it's just if you focus on the axiom feel alone power sponsor global symmetry is exactly the not what she meant by a tough naturalist so in that sense of global cemetery is restored.
13:29:43 Exactly. And so naturally exactly in the sense of Professor Weinstein mentioned so back to that question just want to clarify.
13:29:52 Thank you Dr. Alexander and or last question that we have our we closer to proving string theories existence.
13:30:01 This that's a good question because, again, I remember when I started grad school and they thought how like how can we prove string theory because you have to be an energy they're so strong, but this would actually be an avenue to do it, if we're able
13:30:17 to show that one of this is effective field theory that comes from a string theory is the correct one that is going to give a lot more weight to string theory.
13:30:26 Of course I think there are a lot more challenges we have to look at how to compact defy the string theory, but that could be my opinion maybe an indirect way to experimentally probe string theory.
13:30:38 Yeah.
13:30:41 Okay, thank you so much and thank you for all the insightful questions I just want to thank the rest of the NSP team and the student council and the KTP team and of course more gone for this amazing talk, and for being our invited speaker today.