Into the Impossible With Brian Keating - “I only had 30 minutes to Invent Eternal Inflation!” Andrei Linde | INTO THE IMPOSSIBLE Podcast (#310)

Episode Date: April 9, 2023

Please support the podcast by taking our short listener survey: https://www.surveymonkey.com/r/intotheimpossible Watch the video of this episode here: https://youtu.be/Qq2OgL8Hb6o?=sub_confirmation=1 Andrei Linde is one of the main authors of inflationary cosmology. At present, it is the leading candidate for the theory of the very early stages of expansion of the universe and formation of its large scale structure. In this podcast Linde will describe some of the popular versions of this theory, as well as observational evidence it favor of inflationary cosmology. We also discuss Andrei’s career, the big problems in cosmology, and how Andrei invented eternal chaotic inflation which can lead to a universe which is constantly inflating, where new universes are constantly being created. Eternal inflation is a theory that states that the universe is constantly inflating, and that new universes are constantly being created. Here's his 1986 paper about it ETERNAL CHAOTIC INFLATION http://cds.cern.ch/record/167897/files/CM-P00066672.pdf Professor Linde’s seminal book PARTICLE PHYSICS AND INFLATIONARY COSMOLOGY is available in PDF format: https://arxiv.org/pdf/hep-th/0503203.pdf Here are some past episodes that complement this one: Anna Ijjas: Bouncing cosmology https://youtu.be/aGlLjq4OcmE Will Kinney: An Infinity of Worlds https://youtu.be/iDsqy9QVGoI Neil Turok Endless Universes: https://youtu.be/Dt5cFLN65fI Note there are a number of alternative theories to cosmic inflation. Some of the most popular alternatives include: The ekpyrotic universe: This theory suggests that the universe began in a state of contraction, rather than expansion. The contraction would have eventually led to a singularity, at which point the universe would have bounced back into expansion. The cyclic universe: This theory is similar to the ekpyrotic universe, but it suggests that the universe goes through a series of cycles of contraction and expansion. The varying-speed-of-light universe: This theory suggests that the speed of light was not constant in the early universe. If this is true, it could explain how the universe could have expanded rapidly without violating the laws of physics. The string gas universe: This theory suggests that the early universe was filled with a gas of strings. The strings would have interacted with each other, causing the universe to expand rapidly. Subscribe to the Jordan Harbinger Show for amazing content from Apple’s best podcast of 2018! https://www.jordanharbinger.com/podcasts  Please leave a rating and review: On Apple devices, click here, https://apple.co/39UaHlB On Spotify it’s here: https://spoti.fi/3vpfXok On Audible it’s here https://tinyurl.com/wtpvej9v  Find other ways to rate here: https://briankeating.com/podcast Support the podcast on Patreon https://www.patreon.com/drbriankeating  or become a Member on YouTube- https://www.youtube.com/channel/UCmXH_moPhfkqCk6S3b9RWuw/join To advertise with us, contact [e-mail] Learn more about your ad choices. Visit megaphone.fm/adchoices

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I was so upset. I had ulcer at that time because, I think, because I did not see any way to make it work. And then there was a paper by Alan booth together with Eric Weinberg saying that it's impossible to make it work. Then Steve Hawking came to Moscow proving that it cannot be done. But I somehow found a way to do it in new inflation first. New inflation was you start with the similar initial conditions, but not in the minimum potential, but maybe on a shallow maximum or shallow minimum, and after that you roll for a long time. You just need to have this quadratic potential and you feel in the beginning of the universe to stay somewhere out with the minimum, that's all you need.

So it was so simple that this was for me at the moment after that I understood that we are not just doing some logic trick. but if a harmonic oscillator can explain you the origin of the whole universe, that was the moment when I understood this is a time to write a book. Everything is done. Welcome everyone to this extended episode of Into the Impossible with the great theoretical physicist and one of the founders of cosmological inflation, Andre Linde. In this episode, you'll get the full story of inflationary theory straight from the source. How Professor Linde struggled with inconsistencies in the Hot Big Bang Theory

and the direction of his own career to become one of the driving forces for a generation of both theoretical and experimental cosmologists. From quantum fluctuations to predictions of pocket universes, this is science from the source. Please keep into the impossible in your feed

by subscribing and following. And for some extra credit, jump over to our YouTube channel at DR Brian Keating. That's Dr. Brian Keating and subscribe there too, where we just broke the 100,000 subscriber milestone. Be sure to see the video of this episode

where you'll see Professor Linday's slides. Please help make the show better by filling out our listener's survey linked to in the show notes. And please let us know what you think of the show in the form of a review like this one. From Drew Bop, one of the best places to go

for in-depth physics conversations and other open-hearted discourse. He treats his guests with respect but isn't afraid to push back on controversial statements. And now, let's discover how the universe may have begun in this inflationary cosmology episode of Into the Impossible with the celebrated theoretical physicist Stanford professor Andre Linday with your host, Brian Keating. Any sufficiently advanced technology is indistinguishable from magic. Open the pod bay doors, please, how? Welcome everybody to a very

special episode of the Into the Impossible podcast. I am your Formerly fearful host, Brian Keating, who started the podcast three years ago in a time of a pandemic when I wanted to speak to the world's most brilliant minds and explain some of their ideas and bring to your attention so that you may ask them questions. And today is no exception. We have Professor Andre Linday of Stanford University. And Andre, I couldn't resist. It's kind of mandatory now to ask chat GPT about all these things. And it got most of it right. It did say, however, that you co-wrote the book, Faith, Fantasy, and Fiction.

But that's not right. That was Roger Penrose, past guest on the show. But otherwise, it's pretty good. Andre Demetrovich Lindy as a Russian-American theoretical physicist and the Harold Trapp Frees, Professor of Physics at Stanford University. He's one of the main authors and architects of inflation in our universe, as well as the theory of chaotic inflation, eternal inflation, and the inflationary multiverse. Does that sound about right?

Very good. Well, I've been really having a great desire to have you on the podcast for a couple of years now, and our schedules have worked out finally so we can record this in this very auspicious month. So it's a pleasure to welcome you to the podcast. Thank you for being here. Thank you for inviting me. So we exchanged a couple of a dozen evens. about different things. And we also had the wonderful opportunity when Alan Lightman was a guest on the podcast for his second appearance on the Transcendent Brain episode. I'll put a link to that somewhere up here. You were kind enough to ask him some questions. And so the story goes, turnabout is fair play. So we're going to have some questions from Alan Lightman coming up later. But before we do that, we love to do a segment on this podcast called Judging Books by their covers.

And oftentimes there's not much to go on. But I think in the case of your book, particle physics and inflationary cosmology, there'll be a lot to discuss. We'll show a picture of it on the screen right now. It's this magical black cover that I don't know what it's supposed to represent. But Andre, how did you cover? Why did you write that book, that particular book? Well, you know, I was in a strange situation at that time. I started writing it somewhere in 85,

when inflationary cosmology seemed that it has already done. Everything is clear. Well, the first was old inflation, new inflation, then finally my chaotic inflation, and then it was clear for me that the general picture we already have it. So it's necessary to explain what we have because what was already at that time was completely magical.

On the other hand, I hate writing books. I research. And so it was impossible for me to just to stop doing what I was doing and to summarize and every, each time it was possible to be kind of diverted into some different direction and do some other piece of research. However, something changed in year 85, 86, because, you know, I was in Russia at that time, and they have special rules for us publishing papers. And the rule was that before sending a paper for publication,

you need to first get permission from Academy of Science. then to send the request for permission to some other agency, which would check that I would not reveal any secrets of the universe, which would have any importance for whatever. Okay, so each time it took us like three months. But then Gorbachev came to power, and they decided to simplify everything. It was called Perestroika, to remove all bureaucratic obstacles on our way, etc. So removed, they just stopped this agency from functioning, but did not replace it by anything else. So here, there was no agency which would be supposed to ask a permission, and therefore, essentially, we were living with a mouth shut. So if we were able to write something, it was only in the Russian journals, which will be translated a year later.

Okay, so this would put us in a strong disadvantage. And okay, then that's the time to start writing book. So that was how it started, but I hit it enormously. And nevertheless, in the 86, something else happened because I was because of all of these and some other circumstances. Like I was learning for the first time how to drive my car on Moscow, ice and my instructor told me what he thinks about my talents in a special kind of Russian which you cannot find in the books all all this together I kind of got

depressed and so I was laying on the bed I could not do much whatever all doctors told me that I'm completely healthy okay but that's how it was and then suddenly they called me oh sorry for such a long story but that's how it was okay Suddenly, there was a call from Academy of Science saying that you must go to Italy. Ah. At the time, it was absolutely impossible. And only one visit per year in the best case allowed, and now why should I go to read popular lectures of astronomy to citizens of Rome, whatever?

Something totally weird. So probably there was some agreement between academies. And I don't know, I cannot go. So I use my only option to go for this formal thing. And they told me, well, give us a certificate that you cannot go. And I understood that it was serious. Renato went to my wife, went to Elevieve Institute to get something signed by our head of theory division, Ginsburg.

And he loved to that. He said, what the problem is he doesn't want to go abroad? He doesn't go abroad. So he signed something for that. And a few days later, there was another call saying, well, today you say you are ill, but tomorrow you'll be healthy. If you just cannot go abroad, then just tell it to us. And that was already very dangerous. So I picked up some documents.

So long story short, they required for me to send them a new paper for publication to be distributed among citizens of Rome and Turino, whatever, before my talk. And usually it takes a lot of time, but now it was hopeless because there is nowhere to get permission. But they would send it there with diplomatic mail without any permissions required. So it was like a shock for me. And when do you need it? I ask. And they told me better tomorrow. Wow.

And now, how would it go? Okay. So it is totally, totally insane, especially in my state at that time, kind of ill or whatever. And I understood, on the other hand, that are missing my opportunity if I don't do it. So I just grabbed my head like that. So moving in what can I do in half an hour so that I can print it and send it

tomorrow because this is his chance for you. Yeah, you will be laughing when I tell you what was there or I have the theory of eternal chaotic inflation. Wow. And a half an hour. Yes. Unbelievable.

But I was unable to write it at that time. So I sent them some nonsense. but nevertheless, a month later, when I was on the way to Rome, et cetera, I had in my luggage, well, not allowed three papers on eternal inflation, which I took with me. Wow. And after that, when I returned, I was healthy. And after that, I understood that I must rewrite everything which I have written in my book. and that's how the book was.

So it was delayed from the original publication from 1986. I thought that I'm going to publish it maybe 96. I've written half of it with scissors and glue because there is no computer use. Right. So it was not a very optimal way to do things. And then when in the middle of that, you understand that you should actually change it completely. Right. So it was.

Wow. From my perspective of multi-year, multiverse in chaotic inflation. Just a quick pause to ask you for a small favor, while my thumb is occupied with old Albert on it, yours is presumably freed up to leave a thumbs up on this video. It really helps me a lot with a good old-fashioned YouTube algorithm. Thanks a lot. Now back to the video. Now, I remember reading in 1988, 89, I think it was 88, when,

Stephen Hawking's, a brief history of time came out. And you're mentioned in that book quite extensively, and it's not a surprise maybe why Chat GPT thinks that you might have written it or something else. But around that time, there was this Newfield meeting or something. Was the Newfield meeting? Was that before the book came out or after? It was long before.

It was actually the first meeting on inflation in 84 in Cambridge. but before that was him in Moscow in 81 and you had been working on a lecture week

phase transitions and and so forth when did you start when did you did you ever consider yourself

a cosmologist until that point or were you did you consider yourself a high energy theorist what was your self notion

about what you worked on well I thought that I'm going to do high energy physics but then it just well The flow events moved me to cosmology because my thesis advisor, David Kirschnitz,

told me that our phase transitions can be interesting for cosmology. And one thing after another, and then I found myself doing cosmology. But I remember that when I was a student, I sent to my mother a letter from some place with saying that, yeah, cosmology is so interesting, but I am too old to become a cosmology. just. Wow. Those, those impressions could not have been more incorrect, Andrea. We're glad that you didn't, you know, give up on that at that point. But it is still an exciting field for young people, but it's also interesting for people that are more advanced in years. And I remember, yeah, when I was a postdoc at Stanford in the late in actually 1999, 2000, I think you were on

sabbatical, Unanata. So we didn't get a chance to meet back then. And I was a postdoc. And then, But, you know, even then, there were starting to be really interesting times for cosmology. WMAP had been launched and was about to, you know, return some of its first data and so forth. And I don't really, and I don't really recall when the impetus was for you to, or when the idea of chaotic inflation and so-called eternal inflation and pocket universes. I remember reading a scientific American article by you. that was really evocative. And I wondered, you know, when did you, or do you think, let me say it like this, do you think of the multiverse and inflation as sort of related to each other?

There's all sorts of quotes about you on the internet that if you have inflation, you have the multiverse. What is your, can you tell the audience, what is your actual opinion, not just what we might read about in some article? Well, for me, it happened in an interesting way. It was actually in 80s when I learned about the 81, when I learned about the paper by Alan Goose. It was very interesting how it is possible to use exponential expansion

of the universe to solve many cosmological problems. I studied this issue a few years earlier, but I did not know what to do about that. And Alan had this idea how to solve many cosmological problems at once. And then I worked in it, and I was so upset. I had an ulcer at that time because, I think, because I did not see any way to make it work. And then there was a paper by Alan,

who was together with Eric Weinberg, saying that it's impossible to make it work. Then Steve Hawking came to Moscow proving that it cannot be done. But I somehow found a way to do it in new inflation first. New inflation, I am going to try to give a lecture. And old inflation is like inflation in a vacuum-like state, which is called false vacuum. Nothing moves, universe inflates. New inflation was you start with the similar initial conditions, but not in the

minimum of potential, but maybe on a shallow maximum or shallow minimum, and after that you roll for a long time. So inflation happens during rolling. But initially the idea was that you start with quite big bank. So that was kind of given to you that you must. start with the hot Big Bank. And it did not quite work to my own satisfaction. You will say that you solve all problems,

but we actually don't. You start solving them too late after the Big Bank. Already the universe wanted to collapse. It has all chances to collapse before you start, while applying your tricks. And finally in 83, I found this idea of chaotic inflation was absolutely primitive. You just take the potential which looks like a potential energy of harmonic oscillator.

Nothing can be simpler than that. Right. You don't need to any peaks and minima and high temperature. And you do not need cosmological phase transitions, which I studied 10 years before that. I thought that, oh, I'm so happy that my cosmological phase transitions are useful for that. But no, you don't need cosmological phase transitions. you just need to have this quadratic potential and you feel in the beginning of the universe

to stay somewhere out of the minimum, that's all you need. So it was so simple. That is, for me, at the moment after that, I understood that we are not just doing some magic trick, but if harmonic oscillator can explain you the origin of the whole universe, just an oscillator being a scale of you, whatever. garras, the same mathematics described it, okay? So if you just do it and add Einstein equation to this

kind of harmonic oscillator, suddenly everything works. Then for me, it was, that was the moment when I understood this is a time to write a book, everything is done. So, but this was an 83. You said this place was steps from the water. We just haven't found the steps yet. How much did we save? Enough. to get lost. Or you could book a stay with Hilton. Welcome to your ocean front room. Just steps from the water.

The Hilton sale is on now. Book on Hilton.com or the Hilton app and save up to 20% to get the stay you expected. When you want savings, not surprises. It matters where you stay. Hilton for the stay. All right. And it takes from eternity to hear. So you have some slides, a PowerPoint presentation.

Would you like to take over the screen and share those now? So this, I call it universal multiverse. You know, because who we are to say whether it is one or another? And what I would like to do is just to explain you the origin of the question in general. But first, this picture. This picture became like standard. It was produced at some agency here in Berkeley maybe. So it is right now in journals and textbooks.

But many years ago, there was no these left part. No part where there is written big bank and inflation. Everything started with just with a flash. And then the question is, was how everything else later was generated, what is the origin of the galaxies appearing here? And of course, know this, the third image from the right, no blank satellite stuff. It was previously impossible.

So let me try to start with that. But before going to inflation, certainly, before going to that, I would like to give some tribute to Albert Einstein in his autobiographical notes which were like the last thing he wanted to say to

others, this is my life, this is what I was doing, this is what I think about everything, okay? So he died several years later. So he said the following, I would like to, yeah, I would read it because it's so strongly state. I would like to state a

theory which at present cannot be based upon anything more than and a faith, he has the right to say so. The faith, in the simplicity, intelligibility of nature, there are no arbitrary constants. That's to say nature is so constituted, that's possible logically to lay down the strongly determines law,

was that within these laws only rationally, completely determinants constant occurred. Not constant, therefore, whose numerical law it could be changed while destroying the theory. So this was a dream of a final theory, and many generations of scientists were looking at sentences like that. They wanted to find the theory, and we wanted to find a unique explanation of everything. Why, for example, electron mass is given by this. Why proton mass and neutron mass are almost equal to each other.

So find some principle explaining that. one of my friends was living in the apartment number 137, which is, of course, inverse of Alton. And he felt that he's blessed. So here's the question, why this 137? What is the reason? And according to this, we just fundamental constants. We knew that they never changed.

We know that electron was everywhere in the universe is the same. So it's just a constant. We need to understand why it is 2,000 times smaller than a proton. What is the reason for that? Why? Okay, so many things like that. Why electron? Why proton and neuter?

Why whatever? Okay. So the idea was eventually we'll find the theory which explained it. So what happens now, it seems that some of the constant, may be fundamental. And some of the constant, maybe Gelman called them like that, environmental.

And environmental means, well, in one part of the universe, you have one value of, for example, dark energy. We think that dark energy characterized by the number, like 0.5, 0.7, whatever it is, depending on the experiment,

or dark matter is given by some other number. And it must be everywhere in the same universe. But when we introduced inflation, suddenly it's possible to make dark matter and dark energy in a very non-dramatic way, very trivial way, taking different values in the same universe, but far away from each other. So that's what is a multiverse. Many people take it very dramatically like, what is this movie, which recently got the Oscar. Yeah, everything everywhere, all of them. How people regard multiverse right now. Yeah, Andre, I often say there's only one thing bigger than the number of universes in the multiverse,

and it's how many movies there are about the multiverse. Yeah. You should get some credit. Do you get any royalties, Andre, when they make? No. What they did, though, they invited me for the movie. just for the premiere of its movie in San Francisco, but unfortunately, I did not have time to go. It's a pity.

Okay. Anyway, let's go forward. So one of the main goals of inflation in the cosmology when it was proposed was to explain why the universe is everywhere the same, because this is the question, why it is so uniform, why it is so homogeneous? which is one of the questions of Albert Einstein, why everything is like that and could not be any other way, or how he sometimes formulated whether God would have any choice. So this was a question. And we thought that we are coming very close to answering it because we explained why it is uniform, why it's everywhere the same.

But then when we studied further and further, we were up to some surprise, and that's what we are going to talk about. But first, few words about inflation and the cosmology as compared to the standard Big Bank. So in standard Big Bank theory, the idea was first because it is bank. And at the beginning of the bank, the universe was hot. So if we consider a box filled, for example, by a thousand of proteins. So if you take the box and fill it with a thousand of proteins, then the universe expands, how many proteins inside? Same thousand protons, okay?

You start with something, you end with practically the same. The basic idea was that the universe expansion is nearly adiabatic. If you count all photons right now in the universe, which is about in the part which we see right now, it's about 10 to the degree 98 or something like that. So the same amount was supposed to be in the early universe plus, minus, maybe one order of magnitude. Because some non-adiabotic processes happen in the early universe. But roughly, you get what you started with. If you play movie back, you'll see right now a little bit of temperature, and then you play the movie back and you see a smaller, smaller, smaller, smaller universe.

Everything dense, same 10 to the degree 88 particles in the part of the universe which we see right now. So then you have a question, who gave you this 10 to 88 particles at the moment when the universe for the first time opened its size? okay because how is that there was nothing and then suddenly they stand in 88 so that's an interesting question can we do it cheaper like if you hire somebody to build your house and it requires this amount of millions of ton of matter say no but if somebody comes to you and tell you that I can build your house from materials which require you to give me just pleasant one milligram of matter, I would tell you a cheater. Okay. But that's exactly what inflation does. So you can make the universe starting from less than one milligram of matter. And, well, I cannot really honestly say that I'm cheating because it actually follows

from the loss of physics which can be explained, though it sounds extremely, extremely weird. Okay, so back. So what was the questions which we wanted to answer? What was before the bid back? And we still don't know. There are many ideas right now. There are many ideas 40 years ago as well. We started this inflation theory.

But it's probably fair to say that we still don't know exactly. But inflation allows you to approach this question differently and propose some answers, which maybe make sense in the context of quantum cosmology. And quantum cosmology for that was, well, just like abstract science, it was after works by Alex Wilhelmkin, Harley Hawking, well, my contribution and others, quantum cosmology became relevant to what we study right now, though it still sounds like something strange.

Yeah. So then we wanted to explain why the universe is uniform. On that hand, why it is not exactly uniform? Because if you just postulate the principle of uniformity, that was called cosmological principle, by the way. It's in textbooks. In many textbooks, they are discussing cosmological principle even now. And they used to make a joke that some people who do not have good ideas,

they sometimes have principles until I learned that this principle was used by Albert Einstein. Well, anyway, so this is a question. And either you have a principle that everything must be uniform or you are not a man of principle. If you say it can be a little bit, okay, I can take only small bribes. So why it is isotropic. And a simple example, galaxies rotate. Stars will rotate around the center of galaxies. Planets rotate about the suns, stars.

So everything rotates. why the universe doesn't? Okay, so why it is flat, meaning parallel lines do not intersect and do not diverge at infinity, or at least in the place where we live, we never seen this happen? Why it is so large who gave you this, 10 to the 89 or more particles to build the universe? So all of these questions. And many of these questions can be answered with the help of inflation, well, plus some ideas which we gradually were adding on top of it later.

So the basic idea of inflation. Take a box not filled with protons. Instead of that, take a heavy vacuum. It sounds that the cheating starts at this moment. Because heavy vacuum, how is that? Vacuum is nothing, so why vacuum cannot be heavy? Well, it's not entirely true. This is actually one of the main problems of modern physics,

which is cosmological constant problem. Why vacuum is so light? Why, experimentally, density of energy of vacuum right now is less than 10 to the minus 29 gram per cubic centimeter, which is 120 orders of magnitude smaller than plankton density, one of these major problems of cosmology. But in the early universe, well, who knows, maybe the vacuum was different. When we start studying phase transitions in the early universe,

I found that scale of field actually can play the role of the vacuum. And it seemed to me so simple and so transparent, I start telling about these to others, and they told me, no, no, no, this cannot be. or so I've written in a paper about this, but when it was translated into English, it was kind of funny. The name of the article in the Russian was Posteannale cosmological, Postearno, which means, is or whether the cosmological constant, really constant. So it's trying to say that it can take different values in the early universe. But the translator,

translated the title, like, is the Lee constant a constant? And the Lee is the name of a physicist. So it cannot be any crazier than that. And the IP was buried among the papers which were published but never read. Anyway, so suppose you have this energy. of vacuum, which can be stored in classical scale field. And what is scale field? Well, example of that here, like a pionism field.

Everybody knows. Higgs field right now, everybody knows it even better. Higgs is an elementary, the pionist composite. Yeah, yeah, okay. So if this scale field has, large energy. And Scal Field is Lawrence Scalar, which means that I'm moving with respect

to it. I do not see that I'm moving because it's in an variant. It's like vacuum because of that. So it's honest to God vacuum. It's Lawrence Invariant quantity. And if I have the box with this heavy

vacuum, then when the universe expands, it remains the same. It is vacuum. There's nothing there except. scale of field, scale of field does not change, which means that energy density of the scale field does not change. Okay? If energy density does not change, but the box expands, then the total energy inside the box

grows. It is as simple as that. When the volume grows, the total energy inside grows. Of course, every normal person said that, no, I have studied it in school. I know that it's impossible to create energy from nothing. So for this person, I would say, well, you need to take it out into the current expansion of the universe. And when the universe expands, it has actually two types of energies, one energy of matter, and another is energy of space, if you wish, energy of gravity.

And in simple terms, so to say, the total energy is exactly equal to zero, and they're just rebalance it. you can have total zero, which is a sum of positive energy of matter, negative energy of gravity. And if you find the mechanism how to pump energy from gravity to matter, then that's how the total amount of total matter and grows in energy. So the energy of matter in the universe is not concerned. every cosmologist actually knew it, but they knew it the other way around. And it's not just a matter of convention, right?

Andre, it's not just a matter of convention that we, it's not just a matter of convention that we call positive, you know, we call energy that's positive, associate that with matter, and we call energy that's negative. We associate that with gravitational potential. No, it's not a convention. It's actually a theorem. If you study Hamiltonian on the universe of space and time and matter, etc., then it's possible to show that the total Hamiltonian of the universe is equal to zero. If, for example, if you write down the Sherdinger equation or the way function of the universe, you will write it, it would look extremely strange.

usually showing your equation is D. Psi with DTI, whatever, is H multiplied by Psi, but you will see that H is equal to zero. And that's actually a wheel or the weight equation. Right. So it is something which seemed to be totally insane, but actually it is, it is equation derived in 67, well before inflation and everything. And it was called Willard David equation because Willer suggested it and David derived it. But Willer loved it and David hated it.

So anyway, so this is what is a result. But it's just, well, a way to tell that we are not talking about something which we just were inventing on the way to justify things. Right. All of principles. I will formulate it slightly differently. Consider the hot universe, okay? Now, this is a big bank. Everybody knows.

So you know that when the hot universe expands, then every photon in the box loses its energy because of the red ship. It loses energy by helping the universe to expand. Okay? So then the total initial energy of the big bank when it started, is the normals. And then it starts depleting. Okay.

So you can lose energy of matter. Energy of matter is not concerned. It is not a property of inflation. It's in every cosmology. The energy of matter is not concerned. But to find a mechanism how it can grow. That was a trick. How surprised would you have been if the Higgs boson wasn't found?

The Higgs boson is the only elementary scalar field that businesses know about. The inflaton is another one. If we hadn't found it, or maybe the energy that we could come to at the LHC wasn't sufficient, would you have been worried about inflation? In other words, does the Higgs discovery give you more confidence in inflation's truth? Well, in general, there are always a possibility, just like pie mezzan, is a combination of works. So Higgs could be a composite particle as well. So if they found something which they didn't expect, this would not be anything strange.

And if somebody told me, can you do inflation without elementary scalar? Okay, make it from fermions. But Stravinsky did it easier. He just take gravity and he added an extra term to gravity. the IEstei-action is R, he added the R squared, and the universe started inflating if this R-square term is sufficiently large. That's true. He needed to have extraordinary large coefficient in front of it.

But after that, we do not need a scalar. And now we learned how to represent this trick in a form which is equivalent, having gravity plus a scalar. So this is possible to trade sometimes both ways. Okay, very good. Okay, so back to this magic trick. So when you take this box, having like one ground of matter, it expands a little bit, and then inside exponentially large number of, well,

energy, then total energy inside becomes exponential large. And then it decays at the moment. of decay, it produce exponential large number of photons, protons, everything. So it's possible to produce all matter in the universe practically from nothing. So if this is not a miracle, then what is? But that was the idea. So then, formally, just a few equations just to show that I'm not just dreaming. here is the Hubble constant, which is the scale of the universe is scale shown by letter A.

The speed of expansion, a dot, and a dot divided by a is hubble constant. It is proportional in the simple environment for the flat universe. It is proportional to the square of energy density of the universe. Oh my God, what I did in this talk for everybody. I made the wrong equation here. It is, of course, not V squared. It's just V. Oh, oh, can you raise?

Can I stop? X the typo. Yeah. Anyway, shall I stop? No, it's fine. No, okay, yeah, because otherwise, do we have a lively discussion? That's, okay. New inflation.

It's new, new inflation now. No. No, it's okay. Okay, so the fact is that this equation, a dot divided by a is equal to H, has exponential solution when H is constant. Yes. Oh, what a shape. Well, anyway, that is what happened. And the total energy of the whole universe is E to the 3HT.

That's just the simplest equation of mathematical physics ever. A dot divided by A is equal to constant. It's exponent. Okay. Same thing which describe you, well, the chain reaction. So the chain reaction is something leading to explosion of atomic bomb, and here you have explosion of the universe. And then you can produce exponentially a large amount of matter from nothing. Okay. So the idea is absolutely brilliant. And the question is, of course, if something looks too good to be true, and sometimes it is, So one of the questions is, if the universe is totally empty, like vacuum state, how do you even know that it expands exponentially?

Because there is no markers. There is no way to see. There is no particles there and no one observer or another observer moving away from each other. So it becomes a philosophical question. What is the meaningful decider space? In fact, it is a debate which was starting from the Einstein times, Starting from De Sitter. De Sitter invented his exponential expansion of vacuum in 1917.

It is the same year of Great October Revolution in Russia, so I remember the day. Okay. And that is, was ill-interpreted solution for many, many years in part, because in this exponentially expanding space, you can always find the coordinate system in the, which it expands and you can find a coordinate system where it first contracts and then expands. And then you have another coordinate system where you see yourself surrounded by a black hole horizon. So how do you interpret it? And if there is no preferable coordinate system, there is no preferable time also.

And then there is no preferable hypersurface of time where this vacuum should decay. And that is why in this scenario, decay of vacuum starts being totally chaotic. And what was looking like orderly universe, very homogeneous, very large, very uniform, becomes totally non-uniform and non-homogeneous. So that was the point at which Alan knew it, of course, and he had written it in his paper that we have this problem in the end of the paper. So we don't know how to do it. And I read this paper in the hope that somebody will come with a solution.

So a year later, I had my ulcer and no solution. At some moment, the solution came. And well, so the solution was one need to break some roots. In general, inflation theory is very simple, basics of it. It's very, very simple. As I said, a harmonical oscillator or whatever of this simplest equation. Very simple. What was difficult about it is some psychological barriers.

You just knew that you cannot do something. Like, even when Alan said this, it's so simple, it's exponential. Then everybody understood that this must be false vacuum. this must be you must stay here on the top in the minimum and then it tunnel down and a tunneling goes directly to the minimum whatever and I at that I was running well I studied tunneling okay and I was running running some experiments on absolutely horrible computer in the basement of my institute and it spit on me some numbers and peripheral cards, whatever. And I've seen that actually tunneling does not go the way it was supposed to go. Well, sometimes it does, and sometimes it does not. Sometimes you tunnel directly to the minimum of the potential,

and sometimes you tunnel just near the top. And then if you tunnel near the top, or maybe you do not even need to tunnel, then when you are sliding down, you are still close to the top. And if you are still close to the top of the potential energy, then you can inflate during that time. Okay? So the idea was trivial. I got it in summer of 81, and I spent three or more months getting permissions for that. And I understood that nobody will believe me in this.

So eventually, I started writing two other papers simultaneously explaining all details of that, because there are a lot of details. I just said an easy idea, but there was nothing easy in technical details of that. So in the end, I got the permission just at the time when Steve Hawking came to a conference in Moscow in October 81, and they gave a talk at the conference,

and everyone there suggested me that they will smoggle the paper abroad, but at that time, I already just got a perfect. permission, so no need to smuggling. And then next day after my talk at the conference, Hawking gave a talk at Sternberg Institute at Moscow University, and I happened to be there, and somebody asked me to translate, so I translated his talk for an hour. And he was not quite ready to the talk, so usually he would give his student do the talking, and he would correct him with some, but at that time, Hawking will say one word and students, and they were discussing old inflation.

I was supposed to translate this one word, so it did not make much sense, so I started giving a talk. Steve say one word, students say one word, and I say, Stephen wanted to say this. So we continue for half an hour, it was fine. He was proving that it's impossible to improve all inflation. And at some moment, he started talking something more lengthy, and he said, but recently, Andrea Lindy came with a possibility to solve this problem and I heavily translated. And then he continued, but his scenario is completely wrong. And for half an hour, I was translating for everyone why my theory is wrong.

And then I finished and I said that I translated by I disagree and explained why. And then I asked him, do you want to discuss it? He says, sure. Well, so we became friends. So that was very interesting. And after that, with this symposium in Cambridge half a year later, where I was invited and by miracle was able to come. So that's how it was.

Anyway, so this breaking the rules, first breaking was you're not tunneling down to the minimum, but you just hang around near the maximum for a while and then slowly move down. So the idea was good, but then when people started studying what happened on the way, et cetera, et cetera, at this Nafield symposium, it was found that in this scenario, perturbations of density produced during inflation, in the simplest versions of this scenario, they are too large and scenario died. So the scenario lived for one year and died pretty quickly. By the way, a few months after I suggested the scenario, it was also essentially the same scenario was proposed by Stringerton, Albert, here in the United States. Anyway, this scenario died.

And it was understood, more or less, clearly. There was some hope, maybe, when we were flying away from this Nafield symposium in summer 82. But, well, there was always hope that we will resurrect it somehow. difficult to bring all of these things together. And then eventually I invented this chaotic inflation scenario, and it was so much simpler that basically it provides the framework for a large variety of other inflation scenarios. But at the beginning, not everybody wanted to believe,

Steve Hawking instantly believed, and that was the only scenario here later. to follow it with his own modifications. So the idea is that you just take scale a field, you don't need the maximum. You don't need metastable, false vacuum, minimum, whatever. You don't need high temperature. You don't need anything. You don't need hot universe.

You have just a speck of space. It can be as small as plankton size. It cannot be any smaller than. that. And if it has a sufficiently homogeneous scale of field in it, then the scale of field wants to go down. But equation, one of this equation is, oh, okay, one of these equations for the scale of field rolling in the universe contains a special term, which looks like a friction term in the equation of motion for harmonic oscillator, three h5 dot. That's a very strange term, but that's not something which we invented. It's just, well, you study

scale of field in the current space, you're right equation, you find this term. So this term freezes this scale of field when it rolls down. So even though it is sliding down along potential, then it slides down extremely slowly. And because it slide down extremely slowly, it works as if it were a vacuum state. F if, as if its energy was just the potential energy, practically no kinetic. And then in this case, the same magic trigger, the same equations which were previously applied for the vacuum, worked for this as well, and you have inflation. But then when scale field became smaller, expansion of the universe becomes slower,

Hubble constant becomes smaller, friction term becomes smaller, and scale field start oscillating. That's all. Okay. So you start with the field hanging on the wall. kicking to the wall, sliding slowly, slowly, slowly. And when it is near a minimum, it starts oscillating. When it starts oscillating the process by which the scale field produces particles, decays into these particles, and you have caught big back after that.

So that's it. You need a harmonic oscillator and the lucky scale of field, which was, well, unruly, hanging at some height to start with. So for me at that moment, the question is way the inflation is something specifically invented or whatever. When you have it in the theory of harmonic oscillator, that's something way more than I expected. What I didn't know. One thing I've always wanted to ask you is when you have reheating, typically if you're looking at it as a friction term, in say molecular statistical mechanics, the energy.

friction is generated by matter, right? So here, the friction is occurring in an abstract space, and it's because of the Hubble expansion. Yeah, if you just keep this equation, nothing creates. Scale field just loses energy, and it's kinetic energy becomes small, small when it oscillated, loses energy.

It can lose all energy. What you need, you need to add some terms describing being expansion of the scale field with something else. Yes. So then what happens is very interesting. You have this harmonic oscillator, scale of field. And it interacts with other fields staying there in vacuum. Like there are particles, they are not yet present there, they are in a vacuum.

But then the scale of field changes masses of these oscillators in vacuum. And this is non-adiabotic process. So when you change the mass all the time, then you excite these perturbations out of the vacuum state and the universe reheats. There are alternative mechanisms of that you can oscillate, can just simply by oscillating, you will calculate some diagrams and you see that the diagrams have imaginary part. So you really need to work. Yes. Reheating doesn't come for free. There's not just all these equations.

you need to have quantum field theory on top of it. Okay? So let's move forward. So you start with, say, plankton mass, 10 to the minus 5 gram. Okay. Then this plankton mass 10 to minus 5 gram, it has a size, 10 to minus 33 centimeter. It's nothing, okay? All right.

And as later, Yerlienkin, well, actually, his idea came a year before, but in a different context. You can create the universe from nothing. Just by high study this way function of the universe, maybe something happens. And then we, well, whatever, this is a separate story. So let's just start with this Planck and domain. And it may be very inhomogeneous to start with. But what happens is inflation makes it homogeneous.

Okay. It may start with large kinetic energy, but inflation sucks away this large kinetic. energy. So if in the beginning, potential energy dominated, then you have inflation beginning in that case. This was a very easy idea. In GR, nothing is very easy. So the really detailed calculations which resulted exactly to the same answer, which I just told you, were completed just a year ago. But before that, there was many other calculations. But essentially, that's the idea.

So if you make the universe not extremely in homogeneous and not extremely large kinetic energy, then sooner or later it becomes inflationary, and that's the solution of the problem of initial conditions in this context. But again, just to be clear, for people that aren't experts in this, this does presuppose and you could make the mass smaller than the plank mass. There's nothing magical about the plank mass. But it's a very high density per cubic centimeter if you calculate, divide by 10 minus 3.33.

But it does presuppose that there is an existence of a scalar field. And people will ask the question, where does that come from? Just as I'll ask, where does God come from? So how do you think about it? How do you think about where does that scalar field come from? It's always eternal. Yeah, just like one of the examples is the Higgs field, where this Higgs field came from. Our nature is complicated.

There are some fields which are like fermions, okay? Why fermions? Where are fermons came from? Oh, okay, sorry, that's electron, how you live without electron. That's so easy. It's a Dirac equation. Oh, Dierke equation is so complicated. Okay, let us do something simpler.

We have vector fields, like electromagnetic field. It's simply, it does not have all of these complexities with anti-commuting variables, etc. So you understand what the vector field is. Yeah. Okay. So the scale of field is something like electrostatic potential. Yeah. It's a little bit dishonest what I just said, because electrostatic potential is the zeros component of a vector.

Okay. But if, for example, if you are surrounded by an electric field with a vector, a constant potential 110 volt, you never see it. It's like another vacuum state. Okay. So if you have 110 volts in the US and you have 220 in Russia, don't touch them by two of your hands, okay, because you'll be dead. But if you are everywhere 110, you don't even know that it is anything. You need to have zero. Now, I remember the first time I heard you speak about this, Andre, You talked about a bird and you said the bird is standing on a wire and it's okay as long as the bird doesn't put its foot on the ground and the other foot on the wire. It'll become a cooked.

How do you say, pittice? Is that bird? No, it becomes fired. Such birds evolutionarily disappear. That's a phoenix, right? Yeah. Okay, good. Thank you.

Well, so the point of that you start with pretty soon. theoretically, ideologically, pretty simple construction. Whether this simple can be really realized in nature, that's a question. Whether inflation happened with a simple scale of potential, which is quadratic. The answer is no. And this answer is a result of experimental studies of inflationary cosmology. The scale of field with the potential M squared, five squared, would produce the spectrum of, but I did not tell what spectrum.

Anyway, going forward, this theory was several years ago ruled out. But instead of that, with some magic transformation, you can save it and make it completely consistent with all presently available data. That will follow up. But right now, this was a nice model to look at, to explain the simple. idea behind inflation. So the idea is then that all matter in the universe was born after the decay of the scale of fuel during

inflation. And there's something else. When we create this red ball, because of these expansion, all in homogeneities which surrounded the ball were stretched it away. Like, think about Everest here. Okay? Let's

stretch it horizontally 1,000 times. It becomes a plateau. So that's what inflation does with all previously existing in homogeneities. The ball becomes totally homogeneous. Its surface becomes flat. It's just like the Earth is flat unless you can travel around it. But traveling around the universe of this size is kind of complicated, technically. So the universe becomes flat.

That's one of the predictions of inflationary cosmology. Let's see what happens later, but then the question is, where the galaxies came from? And the answer was that if we just stretch and don't do anything else, then sorry, the theories are already ruled out because we see galaxies. But we were lucky to have some people who are sitting in the office nearby or whatever studying quantum fluctuations in the early universe. And what happens is this. You have quantum fluctuations even right now in this room. They appear, disappear, appear, disappear. You will not care about them.

On the timescale which we have, you just see nothing. You say this is a property of our vacuum, some quantum fluctuations. But during inflation, well, the whole inflation was lasting 10 to the minus 36 seconds. So small things was not a concern for inflation. It was actually pretty interesting. So you have some fluctuations jumping from the vacuum, but then inflation within a very short time, stretch it. Okay?

You have a wave and it stretched it. And when the wave lengths of perturbation becomes large, then if you write down the full equation for the scale of field, it comes. It contains some gradient terms, it can take kinetic terms, and kinetic term leads to the freezing of the scalar field because of the Hubble constant, the 3H5. If the scale of field tries to move fast, it tries to stop moving fast. So when the oscillations are very, very fast, then it's very hard to stop them, but when the universe expands and the wave lengths become large,

then this dominant term in the equation for the scale field becomes this 3h5. And the scale field freezes. So you have these quantum fluctuations and Bach at some moment is stop oscillating, it freezes. Then on the top of it, another one freezes. And on the top of it, another fluctuation freezes. And you have this mountain, one oscillation over another over another. this resembles me something which I've read as a child. There was these stories of Baron Minhausen.

I don't know whether kids here learned it or not. There was a famous liar, Baron Winhausen. And he once will travel to Siberia when it was extremely cold. And he said that, well, it was so cold. I was trying to call for my friends, and I tried to, well, produce some sound with my horn, but the sound did not go away because it was so cold that the sound was frozen inside.

And then I, well, may a cave for me and slow, and I was sleeping there, but in the morning sun appeared again. And then suddenly I hear the sound, poop, pooh, pooh, pooh. this is the sound of my horn was defrosted. Bying. Well, so that happens in inflation.

What was there frozen sound, it was defrosted, and it was the origin of the structure in the universe. These inhomogeneities, which were produced, they produced because they were in homogenities of density when you have a large field, you have larger energy density. At this place, you have galaxies. So you have a mechanism of production of galaxies in the universe. I super simplify the mechanism, in fact.

Okay. Super, super simplified, but that was a mechanism. And when these two men were sitting in the office nearby, they studied for patients in the Strabinski model, in fact. Okay. And they told me that we know how to produce galaxies from nothing. And I told them, okay, guys, be serious. Quantum fluctuations, okay?

How can you produce quantum fluctuations from nothing? And they explained me. And then I remember that this is related probably to something abstract, like this maybe quantum gravity corrections, R-square-terms, the Rabinsky model. And then I learned actually that this is actually what happened. with any scale of field in the universe. And once you understand,

you understand something very, very important that galaxies can be created from plant of fluctuations. That's insane. You know, well, whatever. No, it is. And, Andre, you know, one, we're not going to talk about alternatives to inflation very much, if at all.

But one thing I've pointed out is that all other models, whether it's the conformal cyclic model, whether it's the bouncing model. They all have scalar fields. So what you just said holds for all the rival theories, including those of Sir Roger Penrose and Paul Steinhart and Aegeus and Neil Turr. So nobody can, now, I would find it very interesting if there was a model of early universe

cosmogenesis that doesn't have a scalar field, that would be wonderful, if only for the variety of ideas, not for, you know, comparing. So anyway, I think what you just said is applicable, just so my listeners, many of whom are cosmology. This was going to appear in one of the slides of my talk. Oh, wow. Okay. Because it's centrally important for what I'm going to say about it. Very important.

I think it's a very, and people don't talk about it. All the people who say that, well, multiverse is your problem. No, multiverse is a problem of everyone who uses similar mechanism. Okay. We'll return to that. Good. Not a problem, but an advantage. Okay?

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the idea is right many years later? Because, well, many people say, okay, well, inflation just does its work, but maybe you can you prove it? There are so many different models of inflation. Can you disprove all of them? Can you disprove the idea? So let me tell you something. I'm not going to stay at each point because there are 10 different points here to discuss.

I'll just briefly mention some of them. The universe is flat. Omega 1. This is a prediction of this model. So it is experimentally shown to be almost flat with accuracy about 1%. Now, I would say this is a victory, this is what inflation does, it predicts, and that's what we found. But on the other hand, there was a time in the theory of inflation in cosmology in the middle

of 90s when the general consensus of cosmologists was that omega is not equal 1, which means universe is flat, but omega is equal approximately 0.3, because all known dark matter together contributed only to 0.3. And then what was our situation at that time? This was a near-death experience. Okay. It's just, well, to those people who ask, is it possible to disprove the whole idea of the universe

just like that? So we had this near-death experience at that time, and several people start proposing models of omega-1. non-equal to one in inflation in cosmology. And I also contributed to that. And then what happens gradually, we have found that these models are extremely ugly. Most of them simply do not work. The first model was proposed by Neil Turek and others,

and in the representation, it just did not work. Okay. I will not describe all the reasons. There are some models remaining working. I know one of them works completely ugly, and I'm telling you honestly because it was my own model. It was extremely ugly, but it worked in principle, but it was extremely ugly.

So in principle, it is possible to do omega-none-equal-2-1. You make the radius of curvature large as you want. you could be open or closed, right? I mean, there is data from Melchiori or from Plank that Melchiori and others and Kamienkowski have claimed are, you know, three sigma inconsistent with flatness, but they require a radius of curvature of 80 gigaparsecs. So at that level, how is it really decide? Yeah.

One way another, I'm just saying, the following, that being very, very inventive, you can avoid the prediction. So you can have models which makes the universe slightly open or slightly closed. I'm just saying that it's extremely difficult. So those people who would say, oh, such a beautiful model, at some moment they will say, oh my God, this is not as beautiful I want. Okay, so this is a real life. You want to have a beauty, but you have what you have.

No, it is right now at least close to the beauty at the moment. The observable part of the universe is uniform. It's kind of uniform, but it's exactly as non-uniform as it should be. And if you say, but was it a prediction because it was okay, that's this cosmological principle that it must be uniform. But nobody in you how uniform it actually is. People expect to have deviation of homogeneity at the level 10 to the minus 3. excuse me, let me drink some water.

So I remember how, in the very beginning of 80s, Nikit Novikov, who was a famous collaborator of Zildovich, came to and said that, well, inflation in the universe is ruled out because it must produce quantum fluctuations at the level of 10 to minus 3 to describe whatever. And we studied this 10 to the minus three experimentally and we found nothing. So no, this theory cannot work. And then dark matter was discovered later.

And with the count taken of dark matter and all other stuff, we are living right now with amplitude of perturbations, which is like an order of multiple smaller. But this was for some of us a near-death experience. When we knew that this theory predict something which is already ruled out, already ruled out. It is isotropic and in particular say it does not rotate. Well, okay, you say it doesn't rotate, but we did not know that it does not rotate with this degree of accuracy. The prediction was that it doesn't. But with these degrees of accuracy, you

is required to have Planck satellites to study it. That's right. Even the first model for polarization was by Lord Martin Rees, who was one of There are many guests on the podcast. And his model was that the universe to generate polarization had to expand anisotropically with the quadrupolar distortion. And he was right that the universe is polarized, C&B is polarized, but for the wrong reason. So that could have ruled out at a very early stage,

but it didn't, right? Yeah. Well, so perturbations produced by inflation are adiabatic. It could be that the curvature. Some people who I know well in my own Liberty Physical Institute, they were talking about rotational like vertis perturbation, whatever. So lots of different models survived idebatic and the idea about it is what inflation always produce and as a courage it can.

Yes. It cannot produce vector perturbations. So far, all models of inflation produce a. scale of perturbations or tens of perturbations but cannot produce vectors. So if there is a question, hunt for inflation, let's kill it, let's find vector perturbations. Well, it will probably kill either the whole theory or the theory not including cosmic strings, which if you add the pepper inflation a little bit by cosmic strings, they will produce you different types of perturbations, including vectors if you want.

Okay. So it's possible to avoid the problems, but it is extremely difficult to avoid them if these problems arise. So is it possible to disprove inflation? There was one of the questions which always asked. The answer is, yeah, it's possible at least to make life of people who will discuss it extremely uncomfortable. Unlike perturbations produced by cosmic strings. Okay. So in the beginning, I remember, how Robert Brandenberger who was writing more many reviews on the situation at that time, his review

was always divided into two pieces, cosmic strings and inflation and the immorality. And they more or less were on the same line. He was trying to prove that either can be right. Of course, he never mentioned for whatever reason

that cosmic strings do not solve the homogeneity and isodric and other problems. They at best can produce your structure in the universe. And then later we found that it does not do this structure properly, experimentally, because they are not responsible for so many peaks in the spectrum which appear in inflationary spectrum. But again, this was that experience. Do you find the peaks or you do not find the peaks?

the large this is very delicate thing because at some stage when you okay the peaks whatever but is it possible

just to do something like not to do philosophy but to do something with the universe so that concerning this

adiabotic perturbation that everything would be fine and still nevertheless inflation do that. Could it be possible? And the answer came after WMAP in Planck they have shown

anti-correlation between temperature perturbations and these modes of politicization. So when this thing appeared, some other models will pass away.

Then inflation and perturbation, have a nearest flat that not exactly flat spectrum. Okay? So now one not exactly flat and what means flat? Flat means you take one scale and then you take a scale 10 times bigger and then you take a time scale 10 times bigger. Perurbations on each of these logarithically scaled scale or exponential scale

scale scale must be approximately the same. That was specific thing that inflation does because, Because if there's a slow roll, whatever, the amplitude on this exponential scale, scaling 10 times and 10 times, approximately should be the same. That was a prediction. Okay. Prediction of 81. This is Zeldovich.

Right. Oh, well. No, that is the thing. Yes. Zeldovish is flat. Zeldovic is perfect. The fact. Degovic wanted.

He did not predict it. He wanted to be flat. This Zildoich and Harrison. And so what people who did inflationary theory wanted to do, of course, he wanted to reproduce Zildoich, okay? So when Mujanoff and Chibisov tried to reproduce Zildovic, they obtained a disappointing result. They produced spectrum, which was slightly not flat.

And then wise people, they published it and saying that what we predict is similar to Dier-Dowage, but it is not flat. This was their second prediction, that it is flat, but logarithmically different from this. And that was the second prediction. The prediction could be right and could be wrong. So it seems right now that it is right. Well, several other things here. I will go. We should just say, Andre, why is it deviate from one flatness because inflation ends, right? If inflation... Yes, exactly, exactly.

Because the field initially was large, Hubble constant was large, the scale of the field was moving slowly, then it stopped moving faster, then it stopped moving faster, then inflation ends. Okay, so on the way to that, things change. If Hubble constant were constant,

oh no, I shouldn't go there. Because if it were constant, then in fact we are back to old inflation where Delta Rho is over one. So right. Yeah. So now let's go to the point 10. That was yet another near the experience which did not happen. Somewhere in 2012 or 13, oh my God, I am already talking for now.

It's okay. Don't worry. Don't worry. No. Yeah. For more than enough. Okay. So in 2013, maybe this is episode one.

We can go and look. I have plenty of storage on my computer, so don't worry. Yeah, but my vocal court. Yeah, if you want to stop after, you know, a little bit, we could stop, sure. Okay. But let's finish up the episode. Well, there was some rumors that. that non-gaussianity is going to be reported by WMAP based on their recent results.

I ask people from WMAC, they say, we don't know anything who told you about that like that. But nevertheless, everywhere very, very worried and very interested. Because, you know, everything is already known about inflation, but if we can produce non-gaussianity, then there are so many different versions of inflation. So all postdocs were enthusiastic because they have so much work for them already if non-gaochani. And also because if non-Gawashani special type will be found, then all, I mean, all single field inflation and models will be ruled out. That would be such a statement. Of course, you'll say, okay, let's add other fields and it's possible to do so.

So people studied different models producing large non-gaussianity. It was possible. The models were ugly, but there were many of them. So, well, and then suddenly there was announcement from Planck. At that time, I was in Europe. I was boarding the airplane returning to Stanford, and Renata College, my wife, sent a message. that people from Planka were making an announcement right now,

and I am boarding airplane. And she texts me one word only. No, no Gaussianity. Okay. So everything. And you had written a paper with her, Supercurvaton. Well, you guys were looking for large curvature. It was with Mujan.

Well, but in terms of supergravity, sorry, yeah, Mukhanov and Demets. Yeah, okay. And honestly, Mughanoh hated curbatans. Well, it's a different story. I'm trying to say that it was like that. It was possible that they find a very significant non-govasion. It's still possible, okay? And that is why cosmological experiments are so significant.

Because if you find some specific types of non-gaussianity, even at very low level, it will rule out enormous amount of different models, and we will need to reconsider what we consider nice and not nice, whatever. This just answers the question, whether we are talking about experimental science, or whether we are talking about metaphysical developments or making people happy because they have something simple explaining stuff. Well, as you see here with these ten points, it's very much physical science which can be, maybe it is difficult to rule it out the whole thing, but every particular model can be tested and ruled out.

In fact, this is what this Planck satellite was about. We studied different models. They produced these marvelous images all across the same. all across the sky, and they ruled out quite a lot of models. They produced these images, which each point is, in fact, should be considered a separate experiment for different wavelengths. They found the amplitude, and whatever, they produced, ways on the curve, which is, well, the curve which correspond to some relatively simple inflationary model.

And then other experiment came and the very recent ones. And they are finding more and more peaks here. So we are learning quite a lot. And then it is possible to continue this way. So this is very experimental science. And this is possible to test it even better, but of course you know better than many. It is possible to study gravitational waves as well. Gravitational waste produced by inflation would be a magic source of information.

They sometimes are sold like what is called smoking gun for inflation. I think that this is a big dishonest salesman pitch. Inflation already has enough evidence in its favor, And smoking gun is the criminalistic tool of 19th century. We have many other tools at our disposal. So if we find Pimauds though, gravitation waves, it will be fantastic not only for inflation, like one very significant evidence in favor of inflation, but also for quantum gravity and quantum cosmology in general.

And also because they would bring us information about the interaction. at energies like many, many waters of magnitude greater than what can be obtained at LHC and other accelerators on the Earth. So this would be majestic and therefore it worse all the money spent on them. This is more or less summary of what we had at least in 2018 after the Planck 18 with all of this data. And NS not exactly equal to one, but close to one, as in quant of inhibits, who wanted them to be. And this FNL local is not greater than one as we were afraid, but smaller than one plus minus, a very large error,

which will be removed gradually with experiments. And this picture shows just an illustration how far people went. So this pinky oval is what was, what was it, seven-year blanker W-map results. So these ellipses were huge, and we did not know what is there and what is not there. And there were so many models which would satisfy all experimental data. These two yellow blobs upstairs, this was standard M squared five squared model. It was perfectly good in this situation.

Okay. This, oops, and let me go back. Okay. Okay, so this area here slightly to the left and down is something which is called natural inflation was working good. If you instead of M squared, five squared, do something else. There are some series of other models which are possible. And that is the latest, okay? That is Planck 2018 plus Bicep Kek.

So where we are, you see where is five squared model? up hill and this blue ellipses is what appears if you take into account the data by Bicep. Bicep plus plank together. So 5 square model is far away. Pye model is out. Potential 5 to whatever. Any potential is any degree, phi to the n, phi to the alpha, phi to the beta. They're all ruled out by this set of events.

So if you say, is it possible to rule out many models? Yes. Where is natural inflation? It is out totally. It was sold as a natural inflation, such a natural thing, whatever. It was one of the main candidates for a ruling model of inflation. It is out of this counter. So we need to do something about this.

And now what is this? This is yellow line and red line. And what are these green ellipses in the very, very bottom of it? Well, so this one at the bottom is the Starabinsky or Hicks Inflation model, these two points. Naravinsky invented his model 40 years ago. Yeah. And it still fits experimental data. Or maybe it maybe not exactly fit.

Maybe it's like one sigma out, whatever. or data by themselves are not as precise as we want. And Higgs inflation also feed the data. And yellow and red line, they start a five-square model, and they go down all the way. And these are alpha tractors. And this alpha tractors is a set of models which Renato College I and some of our collaborators invented.

So the idea is this, our collaborator Ross. You take the original model, which we're written with M squared, Phi Square, and you do one modification only. You change kinetic terms there. And then you may even change M squared phi squared term. Whatever you do, if you go to canonical variables after that, you go back to normal canonical term. but potential becomes a function of hyperbolic tunch. And this potential has always a form, which is a plateau.

And these models provide perfect fit to all of the data by bicep and plank. And what is interesting, they provide a good fit even if I start not with M squared by square, what with lambda, five to the force, what with five to the degree to thirds, whatever. Is it important to know what the potential is or that it exists? It starts being less important

what potential is. It starts being more important what kinetic term is. You feel like that's reminiscent, Andre? So nowadays people are talking, well, we measure the Higgs mass, and now the LHC is almost done. Hopefully it's not done,

and it can do a lot of good science. But now the, priority shift to now we have to map out the Higgs potential. Do you agree that that's a good use of the field? In other words, equivalently, it seemed like you don't care what the potential is in inflation, so you only care that it exists. So is there a disconnect? Are people really spending their energy the right way?

Well, it's hard for me to say and to tell my energy colleagues what they should do and what they shouldn't. The whole story about LHC is very interesting. But, you know, because they started with a standard model. And standard model was so insanely successful based on a very, very simple principles. Right. Telling them, now change your principle, please. One of their principles was renormalizeability of the theory. Right.

Because in their context, quantum gravity seemed to be very far away, and so they are doing best. If you take a potential, which is quadratic, it's renormalizable. If you have a quartic, it's renormalizable. If you have it at 5 to the degree 6, sorry, you have a problem. Okay. So it is possible to modify the theory, but you do this modification of anything, of kinetic terms, or of every, you break the premise of the original model. So you should be very, very careful at each of your step.

Because then if you make the theory non-renormalizable and all of your second, third, fifths loop calculation are based on the use of. very normalizability, well, you better watch your step. Right. So in this model, what we've found is that many of the results, under certain conditions, many of the results do not depend on the potential. And the origin of the singular term is actually Escher geometry. It is hyperbolic space. If you do Azure, you do models which are, well, so far, fitting all experimental data.

I don't know what will happen 10 years later, because now we are trying to feed the data satisfying both CMB people and supernova people. And there are some tendency of people who try to satisfy both, to say that, Actually, if we do it, your NS tends to be greater. So we have models which we can do this as well. Right now, what I discussed so far is just a simple model. It's really simple. It's just how m squared twice squared, modify kinetic term, you're done,

you have everything covered, and you can do it. any value of the tensor index. So you can, if you find right now on Bicep, if you find gravitational waves, it will tell you what the alpha is. There is, however, some discrete spectrum of preferable alphas, which kind of follow from string theory and extended supergravity, and that is the work of Orinata College, and Sergio Ferrar.

And one of them is specific, which you maybe already found, whatever. So that's a very interesting field to be discussing. But guess what? I am already more than an hour, well, an hour and a half. I don't know what we are going to do. Maybe I will just tell you how to solve the problem of initial conditions for it. Yeah, that is very interesting.

Yes, please continue. Yeah. So let's take this model with this non-minimal kinetic term here. So the potential in this direction is shown here as a function of the field phi. So it is hyperbolic touch. It is lengthy, lengthy, lengthy, it's very flat, syntotically. And it gives great agreement with experimental data. And this second potential is just my simplest quadratic potential.

Okay. So when Planck produced the results, there was, well, some people and we know who, they said that actually Planck disproves inflationary theory because Plank is favoring the models with a long plata in them, but these models have problems with initial conditions. Okay. So here is a model, which has both of them present. in the same potential. One is quadratic and another is with flat potential. And that's how inflation happens there. You start at as high energy density as possible because then it is my standard M squared, Y squared theory, which is, it will be M squared sigma squared theory. Okay?

And you go up to the plank density. You can easily produce a plankton size domain and this plankton size domain. you can solve problem with initial conditions, and you have inflation. But then this inflation is going to end. So this ball rolls down from the plankton density and fall into the plateau. But while it is rolling, the field phi does not change because the friction term is huge in the horizontal direction. And potential in the horizontal direction is flat, exponentially flat.

So this field phi does not move while field sigma solves the problem of initial conditions. Okay. So there's a two-field. Yes. And after it stopped rolling down to its minimum, then the ball, which is now driven by the field phi, start falling to this minimum of the potential. And the theory is described by alpha tractors, and alpha tractors feed all the data. So, you solve the problem of initial conditions and you will explain the presently available experimental data in one setting.

It was in my paper which was, well, my Leszouche lectures in 2013. And then the same people who claim that all you have this problem, they apparently never looked at that because this... model was known to them and they said that this problem is unsolvable, that we have some data displaying inflation and models. So it was not quite professional, I would say. Anyway, some latest development on that, it was in a paper by Porman and East. They studied numerically models of this type, starting from whatever density and all of this field, it was. all of this field evolving, they just confirmed the expectations we have at that time.

So I think that this question should be just finished discussing, but this is the last one in this series, just how it fits to the latest Bicep data. So I mentioned that there is some discrete set of values of alpha, which would feed experimental data, but also go from the, will be motivated from extended supergravity models. And there is a discrete set of them. The alpha is equal to one-third, two-thirds, three-thirds, four-thirds, five-thirds, six-thirds, seven-thirds. Okay. That's just it.

Okay. Seven norms, whatever, seven-something. And then the upper one. gives predictions show by this almost flat line here, depending on how many holdings you have. And it crosses exactly in half this blue ellipse, which is a preferable results by latest bice. Of course, it may be considered just like a joke, because bicep does not climb, discovery of any R. Because the sigma, the accuracy is comparable with the size of this dark blue region.

Nevertheless, it's kind of fun to see that some of the models, which are the best models we were able to come from, come with. they are already in the area which can be tested, confirmed, or ruled out, just slightly pushing forward. Right. Slightly, who knows, Bicep Kett said that where they hope to improve accuracy three times to reach Sigma 3,000 within five years in the unify the forces with other people who do, well, more accurate a bit of lensing for gravitational lens. So one way

or another, I'm not telling anybody's work here. No. I'm just saying that it's interesting that what previously considered to be impossible that you need to reach insane

accuracy to come close to test something like Starabinsky model, you must go there. Well, seven times no approximately two and

two slightly Straabinsky model corresponds to alpha equal one and this

does it also correspond to R0 like the green ellipses are they at zero or they

you see it on the graph like that it's very difficult to point the ellipse in the

proper place right so originally in all of these Planck models they just

put Straubinsky model and Hexonplation model to the bottom well if you take a magnifying glass and

look at the plotting you see actually they were slightly off okay so they predict

are approximately 0.004 okay I see okay so it's just it's hard to distinguish it

on this plot but it's not actually zero right no So my question, you know, I think what we'll do is maybe we'll do a part two someday, an episode two with in person. I will come up and visit you or you come here for a colloquium.

You have a standing invitation. And there's a lot of questions from the audience and from professors like Will Kinney and Anne Aegeus and others. We'll talk about those another time. But my question is really pertinent to, as an experimentalist, it's very hard to know when to stop, you know, because you can always add on a decimal place. You can always do it. Is there a natural place to stop looking for proof, quote unquote, of inflation?

That there is an actual floor of tensor to scalar ratio. In other words, there's a lower limit. And it's about 10 to the minus six, the tension to scale. And that's because the primary, the CMB scalar, I mean, the scalar perturbation, will have, they'll generate tenser perit, they'll generate gravitational waves by virtue of their first derivative. They'll start, they'll start, you know, it'll be a second order. Scalar perturbations will generate first order tensor perturbations because you have, you know, curvature in motion effectively. It's very small and it's probably out of the reach of anybody's lifetime to measure

to R equals 10 minus six. But is there a goal? I mean, that would also be very interesting because if you didn't see secondary antisotropy of B modes at that level, that would mean that Einstein is wrong, not just, you know, Gooth and Lindayer. So anyway, is there guidance for me and my colleagues as experimentalists? When would you say, Brian, enough? Stop. It's enough money. It's enough time. Is there a region? Or should you always keep looking, keep adding the next decimal place? Ambition comes in all shapes and sizes. At First Citizens Bank, We roll with your goals because we're built for what you're building. Fit for your ambition for Citizens Bank.

Well, I will tell you, starting with some analogy. And that's what happened when LHC was trying to find a supersymmetric particle, whatever, okay? Which was not a very pleasant story. Okay, they wanted a kind of almost not really. promised but they expected to find it. And now they are using this machine further and further and further and the question is, does it make sense to build a new machine?

Because it's going to be extremely expensive. And what is guaranteed that you find anything? Because we just will expect it supersymmetry to be broken at very low scale. In my opinion, the argument was fault. Okay, but that was a lore, okay? This law suggested people to look in this direction.

Well, so they didn't find. Is there anything special that they are going to find there? So I have heard one argument with a person who explained why they need to do it. And when I have heard it, I said, and we need to. She said, and we need to continue doing it because we didn't find anything. I say, what? Okay, that's interesting. And the next step was, and anyway, Chinese will do it.

That was another. Another argument. Oh, whatever. No. I remember. how people from Planck at this first conference in 2013, they asked me some people who are at the head of this Planck. We need to have some goal for the future. And would you suggest us maybe there are some goal like study further because we did not find a cancer perturbations at the level which we studied, is there any reason to go further?

I said, well, you want a polite, honest answer, whatever you want. And it was, obviously everybody needs to have a goal and then to apply for a grant, whatever. And I say, honestly, we do not have any target. Well, there is a target. There are two targets, Starabinsky and Higgs. Would you spend, like, how many billion dollars, which you do not have yet, just having two targets? And I'm not sure that anybody gives you this money.

I don't know. This is a reality. of course, if you talk with the string theory, people I said at that time, they just issued a report listing lots of different string theory models with the targets which they have, and their targets are about 10 to the minus 6. 10 to the minus 7, I would not advise you to apply for grant to study this. So I don't know what to do. Half a year later, I met Ed Whitten at Berkeley and we just exchanged some opinions,

and I told him about this story, and he told me I would definitely advise them to continue search, because it is so fundamentally important. Then we were trying to find out whether we have any other targets in addition to Stravinsky and Hicks and we found them we were going to a conference in my god

no it means getting cold no it's been two hours on drinks yeah right anyway the point was that we just stopped at some burger place on the way. I don't remember the place, but it was strongly recommended to us.

And because it was strongly recommended to us, the line was extremely long. And we sat down and doing nothing, we start using napkins, me and my wife, Renata College, trying to figure out what else can be like similar to and actually what can be doing something interesting and we had something strange on the way of the second

burger we already have it formulated when we arrived to the conference we already have a theory next day because I was calculating at night and this was the first example of this alpha attractors, except for it was for alpha equal one, we thought that it's not possible, but it gave the same predictions, Xterabinsky and Higgs.

And it was totally, absolutely different model, okay? But it gave the same prediction. Now after that, there was this alpha tractors, and what we found that related predictions are very stable to the choice of the potential and depend only on the is of which is geometry. And then I looked at Renato, looking some websites, studying Ayr-Asher. And I told you, Renata, what are they doing? Let's continue working.

And I say, don't... And I know that, you know, she has some kind of mathematical intuition, which beats me. Always, I don't know how it works, but it clicks in a different way. And so I started after her studying this, we have written a paper called Azure in the sky, explaining how all these things fit together. So you have not only a model built for the purpose of doing something interesting. It was some, there was some beauty in it. And we continued this research for like 10 years since.

And still interesting stuff appears here. But then we found this extra targets. So the question is whether there will be some well-motivated targets and until they appear. But right now we have the Wild West with a, H-0 and stuff. So this will change our expectations quite considerably. Just the last follow-up on the alpha tractors.

Are you suggesting that there may be a new observable, you know, like Ada and epsilon are for, you know, the ordinary inflationary relations between consistency relationships between NS and R. could there be an observable potentially in some space maybe fnl or something that connects sigma and five you know could there be some properties of the alpha tractor potential that are translated into experimental observables for people like me this alpha is related to the curvature of the hyperbolic space so by measuring alpha you're finding geometry not or of our universe, but all this space, which is not, of the space where scale of field leaves.

Yeah. Okay. So that's Renata. I would be unable to say anything as... Well, I want to get her on the podcast too. So if you can introduce me to her, that would be great. Okay. Thank you.

So, Andre, just two more questions. One, well, they're both from Alan. Well, two are from Alan Lightman. I promised him I would ask you the questions that he asked me to ask you because you asked me to ask him a question and he obliged and gave an answer. And then I'll finish up with one kind of metaphysical question that I love to ask my guest. So the first two, these two questions are for Andre. From Alan Lightman, not Alan Goose. If the universe is infinite, does that mean there are an infinite number of Andre Lindays out there?

Well, I would say one is more than enough. But seriously, you know, if the universe is really infinite or like it is self-reproducing, whatever stuff, or even if it is quantum cosmology, then yes, everything can be repeated. But the question is whether it's second same or are. arbitrarily close. It's just like if you have an electron, you have a similar electron. But then Pauli law tells you that there is no identical electrons in the box.

They're always slightly different. So when you say whether you can make a zero copy of itself, there are some theorems about impossibility of quantum cloning, I would be unable to quantum clone myself. even if I had enough money. Well, so that's the thing. So the question is actually very deep. The answer is superficial depends on your purpose.

Why, if, for example, you think that anybody kills the second André Lindy and I remain here, no, it is not going to work. Very good. And then his last question before I ask my last question is, how would we prove the existence of other universes in the multiverse? Well, I did not tell you about the multiverse much. No, we didn't. Yeah.

But I will tell you two things. Yeah. The first thing is that one of the main mechanisms, which allow us to talk about multiverse sensibly, is the following. We studied this theory of galaxy formation. which is due to quantum fluctuations. Okay. These quantum fluctuations,

let's talk about Schrodinger cat for a second. Okay? So Sheridan your cat can be dead or can be alive after a certain experiment. And then for 100 years, philosophers fighting with each other, whether it is dead

when I opened a cage and I registered it dead. and then reduce its function, way function for the dead cat. Or whether it was killed at the moment when the experiment started the fixed time, but the live copy of the cat is the second universe, and the dead cat is here because the unitary quantum mechanics disallows way function branch disappear. So it will be many universe interpret it. So it's 100 years. What is different about quantum creation of galaxies is that there was no cap.

I mean, you start with the universe where no galaxies. And then the galaxy appear in one place where another place. You have this uncertainty. It is described by the wave function of the universe, and this way function of the universe has this many, many branches. and they do not start even with a branch containing a galaxy. Galaxy was produced from nothing. So a galaxy can be here or here.

It can be to the right of me, to the top of me, there are maybe two galaxies to the left. The positions of the galaxies is statistics. This statistics is described by the way, function of the universe. This interpretation, the most consistent interpretation, many-world interpretation of quantum mechanics, or many-world, okay. But now in this world already, because the sinusoidal waves, perturbations, they produce chaotically at every wavelength separately. they can be in any place of the size of the galaxy

one wave comes with amplitude up another wave come with amplitude down so it is like this tossing your coin at any place in the universe this is a multiverse

this is multiverse of all possible galaxies this thing seem to be crazy Now, add to this axione field. Absion field is an extremely light field. It does not do anything except for it has slight potential energy. If this potential energy is too large, you have a large dark matter.

Okay? You make quantum fluctuations. These quantum fluctuations put these axions to the top of the hill in one place of the universe, the bottom another place of the universe. So the dark matter can be large in. not large in the same part of the universe. Don't call it not universe what makes you suffer. But that is the trivial calculation,

the same calculation which already confirmed gives correct results for the galaxies. So if the same calculation is applied for axiolence, if you find axioms in the lab, then you know that this is what is going to happen to them. And then the universe will be devoid it into places where dark matter takes different values. Take axioms with very, very slow slope of the potential.

Then it will not move. It will play the role of dark energy. The value of dark energy will depend on where these quantum fluctuations produced by inflation plays it. There is nothing dramatic like string theory, landscape or anything. So what I am saying, and Max Tagmarks told it already, but I guess not many people took it seriously. If you have this theory explaining creation of galaxies in quantum mechanics, and this may be inflation, or maybe epiotic, or whatever,

people stop starting hunting each other theory for that, because if they start using these tools for describing what we already know, if they use them correctly and if they put their ingredients which are normal physics like actions to their theories then you'll have multiverse for free, the same

tools. So then they prove the multiverse. What are you talking about? You take your theory, you trust your theory. Any of the theories. So it's indeterminate, right? I understand that. Well, Andre, I have one question.

I normally ask four questions at the end, but in the interest of time, you've been so gracious with your time. I'll just ask one. So here at UC San Diego, we have the Arthur C. Clark Center for Human Imagination, and I'm the associate co-director of that institution. And that's why I started the podcast many decades ago. And it feels like a decade ago with my first guest was Freeman Dyson. And that was quite lovely. And I miss Freeman very much. And I've become accustomed to asking several of Arthur C. Clark's famous statements to my guest.

And the one I want to ask you is the following. Arthur C. Clark said the following. He said when a distinguished but elderly scientist says something is possible, he is very likely correct or she. When he or she says something is impossible, they're very likely to be wrong. And I want to ask you, is there anything you've changed your mind about? Is there anything you feel like you've been wrong about over your career as one of the most distinguished and celebrated cosmologists of this generation? Do you have any that you may have said were impossible, that turned out to be possible or vice versa? Usually I'm trying to say that in the multiverse, everything is possible, which probably means that.

that I am not yet old by criteria. Oh, but I was in this old man category when I was young. When I told that I will never be going to be a cosmologist. And that happened to be wrong. Very good, Andre. Well, I want to say, Spasiba. Thank you so much. It's been so much fun.

I want to do another part two with all. I'm sorry that I could not finish it, but that's how the universe works. The story continues. You know, Winston Churchill said, this is not the end. This is not even the end, the beginning of the end, but it's the end of the beginning. So we'll have to do a part two, hopefully in person, hopefully with Renata, and it would be a great joy. Andrea Linday, thank you so much for joining us today. Any sufficiently advanced technology is indistinguishable.

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