Into the Impossible With Brian Keating - End of Inflation Theory? Neil Turok’s Bold New Mirror Universe Hypothesis Explained [Ep. 480]

Episode Date: February 24, 2025

Visit Consensus.app and Enter code KEATING at checkout for 40% off Consensus Premium for 2 Years or visit this link 👉 https://bit.ly/ConsensusApp Please join my mailing list here 👉 https://briankeating.com/list to win a meteorite 💥 Is the key to understanding our universe hidden in its mirror image? Are the answers cosmologists seek much simpler than we think? And can we explain the origin of the universe without inflation?  Here today to share his bold new theory is the renowned physicist and cosmologist Neil Turok. Neil, who specializes in mathematical and early-universe physics, is the Higgs Chair of Theoretical Physics at the University of Edinburgh and Director Emeritus of the Perimeter Institute for Theoretical Physics. Recently, he’s been getting a lot of attention for proposing a simpler, more testable cosmological model that replaces inflation with a CPT-symmetric Mirror Universe, explaining dark matter, cosmic flatness, and density variations without adding unnecessary complexity. Join us as we explore this provocative new theory in depth!  👉 ‘Cosmic Inflation’: did the early cosmos balloon in size? A mirror universe going backwards in time may be a simpler explanation by Neil Turok: https://shorturl.at/jr8kd — Key Takeaways:  00:00:00 Audio essay 00:17:02 Introduction 00:20:53 Going backwards in time? 00:26:26 Symmetry and broken symmetry in physics  00:29:02 CPT symmetry and its implications   00:37:56 Mirror universes and Sakharov conditions 00:41:43 Dark matter and right-handed neutrinos  00:57:34 Lambda CDM model and inflation  01:06:34 Conformal symmetry and Big Bang singularity  01:14:06 Dimension zero fields and quantum fluctuations  01:24:56 Anomally collection and standard model predictions  01:32:24 Where do we go from here?  01:35:03 Outro  — Additional resources:  ➡️ Learn more about Neil Turok: 📚 The Universe Within: https://a.co/d/5uzujNz  📚 Endless Universe: https://a.co/d/aJo2yIN ➡️ Follow me on your fav platforms: ✖️ Twitter: https://twitter.com/DrBrianKeating  🔔 YouTube: https://www.youtube.com/DrBrianKeating?sub_confirmation=1  📝 Join my mailing list: https://briankeating.com/list  ✍️ Check out my blog: https://briankeating.com/cosmic-musings/  🎙️ Follow my podcast: https://briankeating.com/podcast  — Into the Impossible with Brian Keating is a podcast dedicated to all those who want to explore the universe within and beyond the known. Make sure to follow/subscribe so you never miss an episode! Learn more about your ad choices. Visit megaphone.fm/adchoices

This week, something very interesting happened in the milieu surrounding the deep cuts to funding at federal agencies due to the incoming Trump and Elon Musk regime, which I'm broadly supportive of these cuts. And that makes me sort of a contrarian in my field of a scientist and academician. Many scientists and academicians are decrying the cuts as essentially leading to the demise of academia and science. I just think that's overwrought. We know of a great deal of abuse of waste that occurs at universities where much of the research in federal government takes place. Not all, certainly, but the research that I do in physics and cosmology broadly occurs primarily at the forefront, either at national laboratories or at universities like mine, UC San Diego. And at universities, very few people know this, but professor who gets a grant for a million dollars at a university like UCSD will pay over 50 percent to the university. It's called indirect or fringe costs. And that, goes to the support of the university, allegedly, it goes to the support of the university, the laboratory space, et cetera. But in reality, it goes to support all the other departments that don't generate any income, my friends, and sociology and Chicano studies, and so forth.

They may have small grants, which are also subject to overhead, but that most of them do not. So, you know, the gender studies department here generates very little income, literature, and I'm not denouncing them at all. I've co-taught in literature with my friend, Ray Armandrout and Pulitzer Prize winner. We taught a class called Poetry for physicists in contradistinction to physics for poets. But getting back on topic, the overhead fringe rate of 50% at UCSD is pales in comparison to that at private institutions like Princeton, Harvard, Yale, Caltech, some of the places I've been to, Brown. And that could be over 60%. So you're talking about less money going to the researcher when they apply and receive at one or two percent.

their million dollar grant from the National Science Foundation, for example, 68 cents can go to the university so that they may have a Chicano Studies Department. And again, I do believe the mission of a university should create Renaissance men and women. But at a certain point, some of those resources are going to support these vast sinecures of bureaucrats, ranging from DEI agencies with million dollar per year budgets with 10 plus people or all sorts of other activities that take place that have nothing to do with the mission of the university as it was conceived in the 60s and 70s and reaffirmed in the 60s or 70s, especially at a public university, but certainly even for the private universities of which I've been associated

with many. So this is a big problem and the people decrying it, even my friend David Kipping decried this on X as well, saying this is an assault on academia and on science. It's, I don't believe. I believe he's being a little overwrought. First of all, the university has never really had a reckoning. These are private institutions, many of them, private institutions charging literally astronomical sums for tuition, being exclusionary, not letting in any more fractional applicants than they did 20, 30, 40, 50 years ago. In some cases, it sticks out to me as, you know, Harvard lets in 1,500 students a year matriculate at Harvard. And, you know, my local Chipotle does three or four times that a day. And it hasn't changed in 50 years or so. I mean, the class has

maybe gone up a few percent. Tuition's gone up exponentially, as we all know. And the quality of education in many cases has gone down because the researchers that are also professors, and it's no means clear that a professor, because he or she is good at getting research accomplished, has any knowledge, discipline, or professional integrity to make him or her into a good teacher. We assume we see a professor that they're good, but they didn't get there. In most cases, at an R1 research institution like UCSD or Harvard, they didn't get there because of their teaching abilities. We have people that are dedicated, only do education.

There are people that are highly dedicated. I like to think I'm very highly dedicated to educating. But that's not why I was hired. I'm under no illusion of that. I was hired to bring in funding and write papers and do research, train students in my laboratory and graduate school, not to teach undergraduates. That's a very distant second or third on the list.

And then to add to that in the last 10, 20 years, the contributions to diversity, equity, inclusion became a prospect equal to teaching and research at many of the University of California system schools, including explicit notation by that chancellor of various universities. For example, UC Davis states that. And so it's clear the university doesn't even claim that teaching is the most important thing that their professors do. And yet, we have to raise tremendous amounts of money to keep laboratories running those of us that do experimental science in particular.

I should say, I have it easy compared to my colleagues that study marine biology or, you know, the National Institutes of Health or whatever. They get tremendously fewer grants. their average age of getting a grant is like 42 years old. And they become a professor at average age 34, 35 years ago, they might not even get a grant from the NIH until they've been reviewed for tenure. And you can guess how that might go. I was lucky I got grants very young, very early. I started as a professor at age 32. I got my first grant at age 32. And I've never, you know, faced a deficit. And I like to think that that's in part due to luck, but I'm very good at what I do. I'm very tuned in to the extracurricular activities that a good research university professor should maintain.

It's not just about your brilliance. It's not just about how you teach. It's about how you promote you, your colleagues, your field, service that you do to make it more prominent. And part of that is communicating to the public. So I put out a post that got close to 200,000 views so far and growing earlier this week, speaking on Friday, the 21st of February. I can't believe February is almost still hard. And I spoke about the growing hostility towards scientists and academics, and the fact that it was 100% predictable. And I said, effectively, it's worth pausing to consider why this is happening. Scientists, in my opinion, like any professionals, they have a moral obligation to communicate to their taxpaying employers. The taxpaying public are the employers of scientists and professors. You may work at a private university. You still have tremendous support via that 60, 70% almost indirect cost support that comes from the public grants that fund your

research, not your salary. Many individual private universities are not paying their instructors. You know, they pay them from tuition or their endowment. But while the endowments have grown, the rate of getting proposals from the federal government funded are have gone down significantly to one in 10 to less than one in 50 in some cases in some fields. So I think there's a lot of blame to go around, but I don't think it all goes to Elon and Donald Trump. I think that scientists who shirk this moral obligation to communicate their findings to the tax-paying public is, you know, kind of at the heart of at least the controllable reasons for why science support is diminishing. And too many of my colleagues operate as if their brilliance alone entitles them to a lifetime sinecure exempt from the burden of engaging with their employers. Again, imagine this is Chipotle that serves six times the Harvard class size every day. And the cashier is working and then her manager comes by and says, you know, what are you up to today? What are you working? What are you working? on, you know, and you can't understand what I do, Mr. Mrs. Manager.

I'm very sophisticated. I use very sophisticated tools and I'm very cultivated to what I'm doing in a way that you can't, you'd be gone in a second, you'd be fired instantaneously. Now, we aren't answerable to the public and a daily, even those of us at a public university. I mean, I've had parents, you know, scream and heard parents scream about, you know, the professors work for me. I mean, try that with a judge or a police officer, you know, try them. I'm saying you, I pay your salary. So it's, what I'm saying applies to private university professors as well as public university professors. And I've seen this from both sides. I've seen it from a side that didn't really engage with the public, my employers, in the way that I believe I should have, looking back on things. But now I see it from the perspective of someone who spends a lot of time and money. I don't get paid to do this podcast. The university gives me no money whatsoever. They don't support my studio, my equipment, my editors, my publishers. I get a little bit of money from advertising and so forth. But, but,

it's pretty minimal. I do not break even most months, but that's okay. That's not why I do it. I do get paid handsomely by the University of California. I'm a public employee. You know, could be higher if I were elsewhere, but be that as it may, I'm very happy here. And I get to work with the most brilliant students, faculty, colleagues. I just did an interview with a colleague, Ben Bratton, who's a professor here for many years. And I followed that up with a meeting with my dean, Dean Christina Hercina, who's just incredible mind. I get to work with really cool people and I get paid to do it. So I'm not complaining. But I do enjoy doing this popularization and outreach. And it's a term sometimes that my colleagues who don't do it, don't engage in it, they wield it not as praise, but as a slight.

And I've seen this with people, my friends, ranging from authors like Jan 11, who's written in many popular books, to Sabina Hasenfelders, no longer in academia. And that's a term that's really wielded to diminish the intellectual accomplishments of these brilliant scientists. And it's tribalism, and it's very worst and most transparent. It's status management. It's, that masquerades as quality control. Let me be clear. This jealousy-driven gatekeeping has real consequences. Consider Carl Sagan, one of the most effective science communicators of all time,

who was denied membership in the National Academy of Sciences, in part because he committed the sin of making knowledge accessible to billions. Billions and billions, as Carl would say. Now, think about that perversity of that incentive structure. We're telling scientists to be obscure, to guard our secrets, to keep our gates, and our knowledge must be preserved and may be segregated and separated, or you risk the professional standing and popular admiration that we crave for us, the attention, and that bringing the fire down to earth, as Prometheus did,

is the gravest sin that we could do. I think it's a pathology, and it's the worst part of academia. It's a culture that too often rewards the insularity and punishes those who dare to treat you, the public, with the intellectual respect that they pay for, first of all, but deserve morally, second of all. And let's not pretend this doesn't matter. At a time when we face existential questions

and challenges that require scientific literacy, ranging from climate change to pandemic preparedness, to an asteroid that's heading towards Earth, which will be the topic of my next audio essay on this channel. We simply can't afford this type of intellectual isolationism, and I can't really be overemphasized, this irony, nor should it be lost on anyone. The very institutions that we as a society have tasked

with expanding human knowledge have developed a cultural norm that actively restricts its flow to you, the public. You're paying twice. You're paying the price for this contradiction and you're paying the salaries

and the research grants of my colleagues and myself. So you shouldn't stand for it. You should demand that things be explained to you. Not every scientist needs a YouTube channel or podcast. But I agree very much

with my colleague and former guest on the podcast, past guests, I should say, not former, but past, Professor Inna Vichick, who's an incredibly brilliant convinced matter experimentalist at our sister campus, UC Davis. And she replied to my tweet that she said, I very much agree that the taxpaying public is our true employer. And she's not just saying that as a public university employee like me. She's saying it as a scientist.

And she goes on to say, but not every scientist has the passion and skill to be an effective public communicator. But what every scientist can do, and I agree with her 100% is one. She says, make our research outputs freely available. at least on the archive, which is an open-access, publicly accessible website, that you can access you out there and the public. Just look up archive. It's spelled arxiv.org. It's actually supported in large part by the Simons Foundation through the generosity of my late great mentor Jim Simons. Number two, she says, not be openly disdainful towards 50% of the public whose taxes we rely on to do research.

I think she's talking about the political division between conservatives and liberals and the left and the right, And that there is perception of disdain, even though most of academia is, I shouldn't even say most. It's the vast majority, 90 plus percent aligns with the Democratic Party in the United States. Fewer than 10 percent identify as conservative or Republican. It's worse in certain departments than others. Actually, physics and engineering has the highest number of Republicans, but that's like saying, you know, the healthiest horse in the glue factory. It's not really that great a flex because it's, you know, 14 percent versus 3 percent, 2 percent in gender studies. or ethnic studies. So she says that. Don't be openly disdainful towards 50%. The rubs, the idiots that are

cutting off the cancer funding and the pandemic funding and the asteroid deflection fund. I mean, that's nonsensical. I don't think that the Republicans, conservatives in my audience or on X or wherever, maybe the echo chamber of choice. I don't think that it is safe to say that they hate science. They don't want vaccines. And they wouldn't want an asteroid deflected. It's saying that they don't like these 100% full-time employee sinecures for things that have nothing to do with the mission of a university. And then part three of her suggestion, Professor Vichick's suggestion is to understand

that when science is translated into legislation, concerns about citizens that citizens have about effects on their lives in pocketbooks are 100% valid. Bravo. My friend, Professor Andrew Huberman, adds, just read the now beloved Oliver Sachs' biography, autobiography. And he tells a story about being attacked and shunned

and only after becoming a bit of a celebrity in a specific context, re-welcome member of science in the medical community. He was ostracized for a long time. People celebrate Oliver now, as they should, but his story is telling. It also has to do with money. And then Andrew says, ominously, no, he says, more on this later. I hope to find out exactly the upcoming topic that Andrew will mention. Then last but not least, internet friend Richard Behil is a wonderful channel on YouTube,

and we're collaborating together on an upcoming expose of what's called Chernobyl. Simon's effects, and we've collaborated in the past on Dark Matter videos, and I'll put some links to that on the YouTube channel. And if you're not watching this, you're actually not able to hear me. Maybe that's a good thing from your perspective, but you're not able to hear me if you're watching on Spotify or YouTube, but you should watch on Spotify or YouTube if you want to see videos of the special kind of additive background footage on my guests on the podcast, but also I have a whole channel on YouTube where I include these podcasts, but also the video is dedicated to incredibly interesting topics in science, technology, engineering, and math,

namely upcoming videos about the answer to the Fermi paradox that may have been hiding under our nose all this time. We'll also be talking a special video in my newly outfitted Keating Lab studio into the Impossible Studio, really my basement in my home, is to discuss how the different Copernican revolutions that were so important to humanity's development are going to be upgrade and updated in the next year or two in the future as we confront maybe the final one of these great debates about the relationship of the centrality of human beings to the organization of the universe. So make sure you do subscribe on YouTube, but stay here if you want the audio essays that you're listening to. So anyway, the perspectives that I talked about converge on the

fundamental truth, and they're shared by Andrew Huberman's example of Oliver Sacks that illuminates how scientific establishment often only embraces scientific communicators after they get external validation. And that's problematic. And then Professor Vichick offers the practical step that communication should be taking place, even if you're averse to it as a scientist. Some scientists say, oh, I'm not good at communicating. Okay, yeah. Well, were you born knowing quantum electrodynamics and Feynman diagrams? No, no, no, I had to learn that. Oh, so you do learn things that you feel are valuable to you. So why wouldn't that benefit you in the public communication and slight popularization? Again, you don't have to have a YouTube channel. Please

don't, don't compete with me. But no, in all seriousness, you don't have to have a YouTube channel, but you can communicate to the public. You can give talks in the public. You can present. You can participate in star parties and salon gatherings and astronomy on tap or science on top anywhere. And anyone can do that. And the best part of it, and the thing that I learned too late in life, but I'm trying to rectify this. This is really fun. And it develops a new tool in your arsenal and a new way of thinking. Because as Feynman said, if you can't explain it to somebody, you don't understand it yourself. And so it will make you understand new ways of understanding what you thought you knew in a new and better way. So the solution I'm proposing, and others seem to agree

with me, I mean, hundreds of thousands of people have seen it and many, many likes and bookmarks, et cetera on this post on Twitter, X. And that's the solution involves institutional change. We need to change academia. We must redefine success metrics to reward public engagement, not to criticize it through jealousy and pettiness. We need to create training platforms for effective communication. How are these students going to learn if we don't tell them it's important? Most importantly, we need a cultural shift that recognizes the symbionic relationship between scientific advances and the public, you out there, and that we can't flourish either one of us without the other. And this finally brings me to today's conversation with my guest, Professor Neil Turrock, who's an eminent physicist

and cosmologist at the University of Edinburgh in Scotland, known him for 30 years, always inspiring a theorist who challenges the orthodoxies in modern theoretical physics. He exemplifies precisely the kind of scientific courage we're talking about, a willingness to question established paradigms and communicate complex ideas to the public. And he learned that at the right hand, if you will, at the strong driving hand of none other than Stephen Hawking. It was no slouch when it came to engaging with, captivating, benefiting from, and benefiting to the public. And I'm sure many of you out there are familiar with the wonderful outreach that Stephen, the late great Stephen did. Neil served as the director of the Permanor Institute for theoretical physics. He's held the chair of mathematical physics out of Cambridge. He's co-authored what became known as the Hawking-Turrock Instanton Solutions. But what makes his work so fascinating is his willingness to challenge the orthodoxy, in particular, of inflationary cosmology, where my bread gets buttered around the Keating household, the multiverse hypothesis and other paradigms in cosmology that dominate without, in his opinion, the evidence to support them. So in this wonderful conversation,

the second time on the podcast, we explore the state of modern cosmology, the importance of evidence-based science, and the dangers of theoretical physics becoming too insular, too parochial, too detached from experimental verification. Neil also shares his thoughts on making advanced scientific concepts accessible to the public without, and this is so important.

I never like it when someone says, you really got a dumbing it down. No, no, no. I hate that. And if you tell me that, I'll be upset. I met a couple of people this week, I probably listening. Oh, you know, I listen to you. You're so good at dumbing it. No. I mean, I know what they're saying,

but that's not my intention. You're not dumb. You're like me. You just devote your intellectual capital elsewhere, perhaps, but that doesn't mean you can't understand what I do. And if you think I'm smart, wait to you hear what Neil has to say. This is an incredible conversation. And if you found it valuable, I hope that you'll leave a comment. And even if you disagree with this long-winded audio essay that I'm putting here, I enjoy talking to you, and I enjoy hearing from you. And I get emails from you at brian keating.com and i love those but i really love it when people comment here in public on on apple or on spotify comments but this is primarily going to audio only formats and that's to leave a rating leave a comment what did you think about this what do you think about my perspective

and you can change it over time you can change your rating you can change your name you can change your review of this podcast so it's not freezing it in stump so don't worry about that and so with that i bring you my conversation at the inimitable neil tarak enjoy so if i literally Take my two-sided universe. There's a big bang in the middle. Out of the big bang comes a universe with mostly matter. On the other side, if you follow time forwards in its natural direction, you will again find, from your perspective, matter.

But if you try to take a global perspective and choose a single direction of time, then on this side you will find antimatter and on the top side you'll find matter. Actually, the universe is completely symmetrical. It's just that we only see half of it. efficiently advanced technology is indistinguishable from magic. Open the pod bay doors, Hal. Neil Turak, welcome back, your second appearance on The Into the Impossible podcast. So good to see you.

Thank you. You've been getting a lot of attention and well-deservedly so for some several interesting and provocative things that are in concert with the way I see you as an intellect who's not afraid to take on the biggest picture topics in all of science, whether that's from the most. micro level to the macroscopic level. I've been just really fascinated with this new topic that I heard about just a few months back with an article that you put out in the conversation, which is a magazine that is sort of online and gets a lot of good contributors. And it's called

cosmic inflation to the early cosmos balloon in size. And then it says a mirror universe going backwards in time may be a simpler explanation. I'll ask you first and foremost, what does it mean to go backwards in time? I had an argument with one of my sons the other day that you can't invent a time machine because if you could, then you could go back to when the time machine didn't exist, and then how would that have ever allowed you to make that jump backwards in time? So first of all, is time travel even possible, Neil? As far as we know, the answer is no.

But from our perspective, the reason for that is we live on one side of the universe. People living on the other side go in the opposite direction in time. So, and as far as we know, that never the twain shall meet. Though, if we get on to black holes, it gets interesting. So it is conceivable that black holes do provide a way of, in a certain sense, going backwards in time. But let me just comment on this because going backwards in time indeed sounds impossible. But in a certain sense, it happens all the time,

because the modern understanding of the electron, for example, as one of the simplest elementary particles, the electron comes with a partner antiparticle, the positron. And so it's exactly the same as an electron, except it has the opposite electric charge. And you can ask why there are two kind of mirror image particles of each other? And the explanation given by someone called Duckelberg in the 1930s, a very beautiful explanation, which is that, according to relativity, particles travel along world lines through spacetime. So if time goes up and space is sideways,

a particle will follow a line or a curve in space time. Now, when you connect relativity to quantum mechanics essentially allows everything to happen, and only assigns probabilities to, so particles can walk through walls, they can do all kinds of things, which were impossible classically. And what Stokelberg thought about is, can a particle reverse its direction in time? So time's going upwards and this particle's travelling along. And what happens if a particle came from the future turned around and went forwards in time? Or from the past, turned around and went backwards in time. So what you would see if you observe one time slice in the space time, you'd actually see two particles.

You'd see a particle coming through the slice in time and then going backwards through the same slice. And now imagine you follow your own view of time as it goes forward, while the two parts of the curve, the two points merge. And for Tuglberg's interpretation is that the particle going forwards in time, is an electron, and the one going backwards in time is a positron. And when they merge, they annihilate. That's called electron positron annihilation. And there is no more particles. They're just photons. They annihilate into photons. And the reverse process is similar, that you can have a strong electric field, which creates an electron going forwards, an electron and a positron viewed from the forwards in time perspective. But if you view it from the particles perspective, the

particle literally goes backwards in time, turns around and goes forwards in time. So we do see particles effectively behaving as if they were going backwards in time. And in fact, Richard Feynman described quantum field theory as an incredibly elaborate machinery to stop us ever observing particles going backwards in time. And John Wheeler was aware of all this and one of the most creative minds in 20th century physics. He had the wonderful idea that maybe there's only one particle in the universe, because we see electrons and we see positrons, and maybe what happens is that there's one particle going backwards and forwards, and that pierces a time surface multiple times, so you would see a

sort of plasma of electron positron pairs. Now, actually, in the universe, there's an asymmetry, they're more particles than antiparticles, but as far as we know, the reason for that goes right the way back to the Big Bang. So our picture of the cosmos, you can think of it as if when the universe was created, there's a universe full of matter on one side and a universe full of antimatter on the other side. So they both look like they're going forwards in time. That's the arrow of time away from the Big Bang. So I would say our picture is really a very conservative generalization of what will you already know in particle physics. The youngest son thinks that we made a mistake.

We should have called electrons negatrons. Because positron is, in this perspective, more fundamental. So I won't get your opinion about that. No, that's a very good point. We'd be less confusing. The symmetries that kind of underline our existence, I think we make too much of them. I've threatened to Brian Green that I'm going to write another book

called the Hidious Universe, which is all about how broken symmetries are really the thing that are essential for our existence, right? If we had a perfect symmetry between matter and antimatter, you and I wouldn't be having this conversation. If we had a perfect symmetry between time, in time, forwards and backwards, left and right. And they've even done studies on celebrities, and they say, well, what do you think makes Brad Pitt so handsome? And they say, oh, they're very symmetric. But then if you take their face and you split it down the middle and you're reflect the left on the right. They look hideous. Isn't it true that the broken symmetry is where all the magic lies in science? No, I wouldn't say that. I would say the whole history of 20th century

physics has been finding the symmetries. That is how relativity came about, that people realized that so-called Galilean symmetry wasn't correct in describing light and matter. Then Eminethe, of course, proved some very famous mathematical theorems that if you have a symmetry, you have a conservation law. And so our understanding of why there is energy, why is there something called energy? Well, it's because the physical system we're talking about, it has the same laws at any time. And because those laws are invariant under translating time, that results in a conserve quantity called energy. Electric charge is similar, momentum, angle momentum. So all of these very basic quantities in physics are a consequence of symmetry. And the simple fact is we look at the large-scale

universe, it's extraordinarily symmetrical. The deviations from symmetry are very small, and they appear to be random noise. And so even the ensemble of the fluctuations appears to be consistent with symmetry. It is the simplest hypothesis that the universe actually respects the symmetry of its fundamental laws. And we think we know the laws of physics, at least to some degree. We know gravity, we know particle physics, the standard model. And those laws have very strong symmetries, one of which is CPT, which is exactly the symmetry involved in this electron, positron creation. And that process respects CPT.

And so our hypothesis is the Big Bang also respects CPT. It didn't have to. It could have broke CPT. but I think the simpler hypothesis is that it respects the symmetries of the laws. Let's explain what CPT is. So there are these discrete symmetries. There are three of them. There are many more if you want to be particular.

But in science, we believe that C and P are both violated, but CPP in general is not. So can you explain what are the highest level kind of indicators of the importance of both CP being violated and then CPP not being violated? Origin of CPT symmetry is in relativity, so it's a little bit counterintuitive that nature is invariant when you do what are called Lawrence transformations. Drink or expand space and can rotate space into time. So they do various things. Laws of physics are invariant under that. A rough way of understanding it is that we have an intuitive sense that the laws are invariant under rotation. If I take your whole laboratory and I, with you inside it, and I rotate it by 90 degrees, and you do the same experiment, nothing will change.

Because the laws haven't changed by that rotation. So Lorenz transformations are the same as that, but they involve time as well as space. So mathematical laws, which, as far as we know, all of physics respects. So have a little Einstein's famous thought experiment, as I mean a lift, an elevator, and the elevator's falling under gravity, so it's freely falling. And now you do an experiment inside that elevator, you can't see the outside world. You would not detect the gravitational field. So locally, the laws of physics obey this Lorentz symmetry.

So then there's a very cute mathematical fact, which is that, now, unfortunately, it's not terribly easy to explain, but because it involves complex numbers. So it involves the imaginary number, a square root of minus one. And if you know Lorentz symmetry is defined as a set of operations that leave a certain length squared unchanged, and that's minus delta T squared.

There's a minus sign with time, and plus for delta X squared, where X is a spatial sign. Now, you can change this into a sort of Pythagoras rule with time being the same as space, if you make time imaginary, you say T is I, tau, okay? Then you get pluses, four pluses. And this is an old trick, in fact, used by Minkowski and all the people in relativity.

Now, in that picture, it turns out that rotations in four dimensions have a somewhat different structure to rotation, to Lorentz transformations. Lorentz transformations have two disconnected pieces, one of which inverts space and inverts time. Okay, and that's the PT, parity invert space, T reverses time. Lorentz symmetry, that operation is disconnected

from the identity, from the Lorentz transformations which you can smoothly deform to one. to one. In this imaginary time world, they're connected. Okay. So basically the answer is that if I calculate something physically, and if it is what we call analytic in the variables, if I can continue from real mementa, energies and mementa, to these imaginary time versions, then this higher symmetry in the complex theory is manifested in experimental results. That's a very method. and probably not a very good explanation of it.

But that's the proof of the CPT theorem, is that one uses complex analysis and an assumption that all amplitudes calculated from quantum mechanics are analytic in this way. But what it really means is very physical. It's easiest to picture with a Feynman diagram. A Feynman diagram says, imagine this electron is coming up and bending for some reason.

So it comes in at some angle. The space is sideways and time is up. So electrons traveling along on some curve, and another electrons traveling on another curve, and when they interact, they exchange a photon between them. So CPT symmetry says, no, just reverse the direction of the arrows. So the electrons go this way.

So interpreting that, that's a scattering of two positrons off each other. They have the opposite charge. They still repel. And CPT says those two diamitudes are identical. And literally what CPT is, you draw all these finding diagrams and just reverse the arrows. And the statement is that reversing the arrows leaves the answer unchanged. But the physical interpretation is now the opposite. Wherever you had a particle, you now have an antiparticle because it's going backwards in time.

So yeah, that's the status of the CPT theorem. People have sometimes guessed ways it could be violated. But nobody has ever constructed a theory consistent with special. relativity which violated the CPT theorem. Even string theory, when I was at Princeton, one of the famous string theorists was worked on for several months the idea that maybe black holes would violate the CPT theorem in string theory, because you could kind of capture a black hole with a string loop enclosing it. And of a lot of hard thinking, they realized that, unfortunately, this didn't violate CPT at all.

Right. No one's ever succeeded in breaking CPT. We often hear that CP violation is maximum. So is it the case that there's something about adding in a third discrete symmetry that sort of cancels and does so in a maximal, the fundamental way? Yeah. So CPT is a consequence of Lawrence invariance, which we have never seen any deviation from, and analyticity, which is basically.

which is basically this mathematical way of using complex numbers in physics. And that's all. It's a consequence of those two things. But C is charge conjugation, just change a particle into antiparticle. P inverts space and T inverts time. Any one of those does not leave the process invariant.

It's only a combination of all three that leaves physics invariant. And essentially the reason is parity and time reversal or space time, symmetries. You're literally supposed to take the space and time you're living in and invert it. It's hard to picture, but goes right through the origin in the opposite direction. Time, that's easier to picture. You just go backwards in time. And C changes a particle to antiparticle. Imagine I have this particle traveling through space time, and now I do PT.

Well, time, the direction of time is the opposite now. So this must be an antiparticle, but I can fix the picture just by applying C. And now I have the identical picture. The C reverses the arrow on the particles line. And with C, P, and T, the picture is geometrically identical to what it was. But it's just that the interpretation is quite different. You start with antimatter and it goes off. Wherever you had an incoming matter particle, you have antimatter particles.

and same for going out. Is this sort of an accounting trick, or is this something that would be manifest in, say, the weak interaction? As we see, as you just mentioned, a lot of the parity-violating effects that we notice, dating back to, you know, the Madame Wu famous experiments with Cobalt 60, would that now just be behaving for anti-Cobalt 60? Or isn't something fundamental.

Would it affect a different force, perhaps, the strong force instead of the weak force? Or would we see manifestations of this effect? No, we know how C, P, and T act on all the forces. The combination CPPT literally takes particles to antiparticles, reverses helicity. If a particle's traveling along with a certain spin, time reversal will reverse the spin, parity will not reverse the spin, and time reversal reverses the momentum. And so a left-handed antiparticle is changed into a right-handed particle by CPT.

It's a complex operation which you perform on any experimental device. But as long as you remember to change matter to antimatter everywhere and to reverse helicities, that's the consequence of CPT. And when we think about the fundamental behavior of the symmetries, is it still true that in a mirror universe, you would still say, for example, have to figure out a way to explain the Sakharov conditions, for example, which we don't have a full on, we understand the conditions, but we don't understand how they're instantiated.

How is that put into effect in a mirror universe? Yeah, it's very neat because the globally, the universe respects CPT. Okay, so if I literally take two-sided universe, there's a big bang in the middle, and out of the big bang comes a universe with mostly matter. On the other side, if you follow time forwards in its natural direction, the direction in which entropy is increasing, for example, you will again find, from your perspective, matter. But if you try to take a global perspective and choose a single direction of time, then on this side you will find antimatter,

and on the top side, you'll find matter. So now if I flip the universe upside down, then it's just the same, but with a different definition of matter. That what I thought was antimatter on this side is, by somebody living in that universe, is seen to be matter. Our proposal is that actually the universe is completely symmetrical under CPT. It's just that we only see half of it. And Sakharov's conditions for making a matter-antimatter asymmetry,

he knew you could not violate CPT. So what he said is, one, you have to violate T, the arrow of time. There needs to be an arrow of time in the universe. And equivalently, you have to violate CP. Because if you violate T, but you respect CPP, you must violate CP. And CP symmetry converts particles into antiparticles. If you're going to make more particles than antiparticles, you have to violate C.P. So now the laws of physics.

we have do violate CP, it turns out that violation is not quite enough in the standard model, the minimal standard model is not quite enough to explain the matter asymmetry we see. But in our mirror universe picture, for a number of reasons, essentially mathematical consistency, you have to have right-handed neutrinos. In fact, these are more or less required in the standard model to explain neutrino oscillations anyway. So I would say the standard model with right-handed neutrinos is actually the minimal version of the standard model, which is consistent with all of particle physics.

And by the way, the right-handed neutrinos are the simplest stark matter candidate anybody knows of. So if you have right-handed neutrinos, they violate the interactions of right-handed neutrinos automatically violate strongly enough to make the matterate antimatter asymmetry. And one of the right-hand-hand neutrinoes, standard neutrinos can be the dark matter.

What we're proposing is the minimal version of the standard model consistent with all known particle physics. And it happens that minimal version in the context of cosmology, and with this assumption that the Big Bang was respected CPT symmetry, in that framework, it explains all of cosmology too. It's the most minimal framework you can imagine. Going through the singularity is a very very simple. very delicate thing.

The whole universe has to go through a singular point. And if I have a chance, I'll show you a slide of how that happens. At first, I didn't think it was real. I woke up to this blinding light, and I was transported to another place. Pluto TV. Then I heard a voice. Come with me if you want to live. There were thousands of movies and shows, and they were all free.

The truth is our scene. It's just so beautiful. On Pluto TV, free streaming of Terminator 2, fringe arrow the 100 nx files may cause excitement loss of sleep and sudden belief in extraterrestrials no credit cards or alien encounters necessary pluto tv stream now pay never before we get to the slides yeah i want to just make sure the the sign poster there for the audience that might not be as familiar with these concepts but of course these are very very deep and and have great import and what i think is so fascinating about this is that it it has the potential to unify the universe

with a mirror universe, a universe without needing inflation, then the concomitant multiverse, a universe that has dark matter, a universe that has dark energy. I'm worried, as usual, that these things are too good to be true. And it slices, it dices, it explains. Did you get all these out in an expected fashion? I mean, were you planning on this? What was the initial?

When you and Latham, Boyle and others started out on this process? Yes. What was your goal? Our goal was initially, I mean, We started out with very limited goal, which was, well, actually just an observation, not a goal. We started out by noticing that in the standard Hot Big Bang cosmology, the space time, when you extrapolate back to the singularity, the singularity is extremely simple in character, namely in the sort of natural coordinates, which are called condominious. formal coordinates which kind of exhibit the causal structure of the space best. In these coordinates, the size of the universe decreases linearly in time.

So the size just shrinks linearly to zero. And this is a consequence of the radiation-dominated universe. The fact that the Big Bang was dominated by radiation. Now, why is it linear? Why is it so simple? It's so simple because the radiation has a very special, mathematical form, which is called conformally invariant. Radiation does not know about the size of the universe.

We kind of know this intuitively from electromagnetism, that an x-ray is the same as a photon, it's the same as a radio wave. They're just scaled up and down versions of the same thing. Now, if you consider radiation in a shrinking universe, going back to the Big Bang, the radiation actually, the equation's governing it, are completely independent of the size of the universe.

They don't even know the universe is contracting. The size of the universe just disappears from the equations describing the radiation. So you can follow the radiation all the way back to t equals zero. Now, if the size of the universe goes linearly to zero, that means it's a straight line. If I draw the graph, size versus time, it's just a straight line. You don't need to be a genius to extrapolate through. a straight line extrapolates beautifully through the other side.

And what happens in the metric, which is the fundamental object in general relativity, it's how you measure distances, the metric involves the size squared. So the metric shrinks to zero like T squared, and T goes negative. Well, the metric just expands again as T squared, and it's totally smooth. Now, we just made this observation that, hey, I can continue the space time through the Big Bang. What does that mean? And then we asked,

could we invent a dark matter candidate which is created in this extended space time without needing any interactions with the plasma in the space time? So imagine, so you see right under neutrinos are the obvious dark matter candidate. The laws of the standard model, do not allow them to have any gauge charges. They can't couple the photons or blue ones or weak bosons,

just not allowed. They do couple the gravity. And so if the cosmos is changing, that itself can create right-handed neutrinos and make them, as it were, out of nothing. So we started exploring this as a way of explaining the dark matter. We could make the simplest candidate for the dark matter work just using gravity. Now, how do you predict the abundance?

when you've got this extended universe, you can choose the quantum state that is CPT symmetric, that respects the symmetry under exchanging the two halves of the universe. And that turns out to specify the state of the neutrinos and predict their abundance. Do you have any constraints on their mass? I mean, abundance. Yes.

Yes. So we predict the mass, spot on. Okay, the mass of the right end of the neutrino must be five times 10 to the 8. GEV. It's just a number. There's no free parameters. Quite massive, yes. Yes. So the way we got that number is just by fitting their mass to the observed dark matter density. Okay, so we haven't predicted anything. We've just said if you fit the dark matter density, this must be their mass. Now what we have to do is figure out what experiment would it take to measure to confirm this. Laptop from neutrino double beta. Actually very weak constraints, but there is a very clear

prediction. The reason is that right-handed neutrinos can couple to left-handed neutrinos, and the left-handed neutrinos are the ones we see in experiments. I mean, these are graded all the time in experiments. So the right-handed neutrino can be very heavy, but the left-handed neutrino very light. And what happens, the ones we see are very light. So what happens is that they can transform one into the other. The right can go into the left. through the Higgs boson. That is how the left-handed neutrinos get their mass. Is this different than the seesaw mechanism?

It's exactly the C-Saw mechanism. Okay. Yeah. So in the C-Saw mechanism, you couple the left to the right neutrinos through the Higgs. Now, if you want one of the right guys to be stable, you do not want it to couple to the Higgs and left, otherwise it'll decay.

If it's very heavy, it'll decay into a higgs and the left. You have to turn off one of those couplings. And so we discovered a symmetry which switches off one of those couplings while leaving, so in other words, one of the three right-handed neutrinos is absolutely stable. But what it means is that the left-handed guy would have coupled two no longer gets a mass, because it's exactly the same coupling that gives the left-handed guy its mass. So the prediction of this model where one right-handed neutrino is stable is that one of the light neutrinos is exactly masses. And that's permissible. We have no constraint.

And it's now being measured in experiments like the ones you're doing. And people claim that within three or four years, we will have very tight constraints on the mass of the lightest neutrino. So if we measured an inverted hierarchy, that would rule out both the, Seesaw mechanism and the mirror universe? Absolutely, yes. Ah, okay, so it's a very crisp test. Very crisp test. Yeah, I mean, it's a null test.

So it's not, we'd much prefer to have a predict a number. No. We can predict the mass, but it's very hard to measure. So it's a null test, but I think if it survives, if the data turns out to be consistent with the lightest neutrino being massless, and by the way, we know two mass differences, so we can predict all three. if we know the lightest one is massless,

we actually know all three masses from existing experiments. But if it's consistent with that, with the lightest going being massless, I think the idea that the right-ended neutrino is the dark matter becomes easily the best theory of the dark matter. It has fewest parameters.

There are other reasons why the right-handed neutrinos have to be there. I can go into that more, but it turns out that to describe the Big Bang singularity as this smooth transition through, essentially through a point, to describe that mathematically, you have to have this conformal symmetry.

Everything in the universe has to respect the symmetry, which essentially says it doesn't know the size. The matter doesn't know how big the universe. To have the conformal symmetry, it turns out you have to have three generations of elementary particles. We explain it on the nose, and each generation has to have a right-handed neutrino.

Otherwise, there's no chance of this conformal symmetry. So this picture is strikingly simple. We have, in exploring it, we deliberately chose to tie our hands. We've said we're not going to introduce any new particle for which there is no experimental evidence, just not going to do it. No new field, no new particle without experimental evidence. And what we have found is that we can explain everything just using the standard model and gravity.

Not to be impolite and bring in astrophysics into the problems, Neil. Sure. What are the implications for, say, the small satellite problem and galaxy structure and a structure formation? First of all, is that a problem or not for your model? There are all kinds of things that may be problems. And it's to some extent it's a matter of taste what you work on as a theorist. You can follow the observations really closely. And you will always find that there are discrepancies with the models at any one time.

And you can get very upset about those things and spend years trying to do models which fit a little bit better. But I think that's one kind of theory you can do, which are very valuable because it's critical thinking, it's trying to make sense of the data. very valuable. We call that phenomenology. That's fine. It's very important work. But the other kind of thinking is to say, no, let us try, let's essentially ignore the ups and the downs in the data, take the big picture and try to make sense of the big picture. And so, for example, Einstein had this clue that all masses fall the same under gravity, independent of their composition or how heavy they are, they all fall the same way. And people didn't know how to interpret that for 300 years.

They had no explanation of this. So Einstein made that the foundation of his theory, that they're all moving in the same space time, and gravity is nothing but the curvature of that space time. That's our kind of shining example. I'm not preparing us to that. It's important to sometimes have permission to be a little bit imprecise, at least when fleshing out a theory.

And I'm reminded of my former governor here, Arnold Schwarzenegger, who said that to make really good gains in weightlifting, sometimes you have to be a little bit sloppy and not be perfect in form. And I wonder if I could use that as a teachable moment for my audience. Could you tell me as a theorist, as one of the world's preeminent theories, what do you say to your students as the experimental minimum, not the theoretical minimum? What should a good graduate student in his or her early career? What should she or he know about experiments in his or her field? What's the minimum? Yeah, it's a great question, and it's becoming more and more difficult. I think at the time I was a graduate student, it was really difficult.

Experiment had kind of set particle physics experiment, at some extent, had separated or from theory. Experiment had become very involved, very expensive, very sophisticated, and mostly issues were extremely technical. Likewise, theoretical physics had become technical in its own. way and so it's very hard for experimentalists and theorists to talk to each other. When I was a graduate student, I kind of started off on the technical route, but realized that my, in fact, my passion was to understand nature. And it is pointless, at least it was, I felt it was pointless to do all this theory without contact with real experiment. The theory is pointless. There

there's an infinite number of theories and you can do it. The maths is interesting. Maths is interesting for its own sake, but it's not what I'm interested in. But as a young theorist, I more or less had to follow current fashions. And I always tried to work on current fashions, like Grand Unified theories, Super String theories, to try to see what in those theories could be experimentally tested. And grand unified theories, for example, predicted exotic objects called cosmic strings. And if we had seen one in the cosmic micro background, this would have revolutionized particle physics. It would have been an amazing confirmation of this theoretical idea. So I worked very hard on that, and in the end we disproved the existence of cosmic strings,

at least above a certain mass, because they're not seen. So I've always tried to take the best theoretical ideas and either, well, ideally you want to confirm them, or second best is you want to rule them out. But what's happened recently is that theory has kind of gone in a million directions, and to a certain extent, it's kind of lost contact with the earlier motivations of theory, which was to explain nature. The major theoretical paradigms, let's say, lost the plot, a little bit of, bit. The theories have become so complex and adjustable. What's happened with the data is the opposite.

The data has not become more and more complex as time has gone on. It's become simpler and simpler. And the Lambda CDM paradigm is as old as the hills. If you told somebody in the 1960s, I've got this model for Cosmos, and here it is, there's Gaussian random noise, scale invariant spectrum. I think there should be a lambda. And there's some dark matter, which might be a particle. nobody would have batten eyelid, right? Lambda CDM is a vanilla, a true vanilla model. I'm not saying it's a theory, it's not, it's a fit. But as the observations have got more and more sophisticated,

they have followed this very simple model to extraordinary degree. Yes. It's a bit like the history of the standard model, the particle physics. People expected when they built the large Hadron Collider, they'd find new particles. All the particle physicists were saying we, you know, just switch a machine on and you're going to find supersymmetry and weenos and be nos and miniature black holes. And there's nothing there. Okay. And so both on the smallest length scales we've probed in particle accelerators and on the largest, nature turned out to be simpler than we expected. In fact, phenomenally simple. Now, my basic philosophy is we need to learn from the universe.

Don't sit in a room and dream up a theory on the basis of nothing at all. Take these clues. These are very profound clues. And so that's the spirit of all our recent work. We're taking these simple observations and trying to interpret them as naively and straightforwardly as possible while being mathematically consistent with mathematics. and nothing is more simple than the number zero. And there seemed to be a lot of zero is the most symmetric number, right? So we have a lot of observations that are basically null.

And then when I met you 30 years ago when you came to Brown University, I remember even back then you saying the astonishing fact about the universe is how simple it is and how close it is to absolute nothingness. And so in that vein, maybe we can start the presentation that you've kindly prepared. What I want my listeners and viewers to pay attention to is that zero is a special number, and it's unlike any other number. Out of all the infinite radii of curvature, for example, the universe could have chosen. It seems to have chosen the one value out of a bidirectional set of infinite possibilities,

the one number that has no curvature, zero curvature. We also see an astonishing degree of Gaussianity. hopefully, well, I shouldn't say this, Neil, and you should slap me verbally if I do, but I often say, I shouldn't say that I'm hoping to see tensor perturbations. Yes, the butter is put on the bread of the Keating household by looking for gravitational radiation and primordial perturbations, but it may not be there and it may not exist. And I don't think I should be prejudiced to that conclusion ahead of time. So as we watch this masterful presentation, I do want people to pay attention to the things that we do know, which is that, essentially the universe is simple and it may have none of the things that would make theorists happy and that's okay because that's the way the universe is. So Neil's going to provide a description if you're listening only. I do implore you to subscribe and watch on YouTube as well. But he's going to take us through. What do we know about the universe? It's curvature, it's perturbation spectrum and especially how those could imply a universe that, as he calls it, a looking glass. I don't

know why you didn't call it a looking glass being across the pond. But take it away, Neil. No, indeed, it's true that a simple universe makes a lot of theorists unhappy because it's not giving signatures of physics. It's giving very vanilla signatures. But, yeah, it may well be that the universe really is extraordinarily simple on the very large scales and very small scales, and all of the complexities in the middle where we live. I mean, after all, we do seem to be the most complex entities we know of in the universe. That's my current view, is I think that will turn out to be correct. Actually, the universe is not built out of Lego. It doesn't get more and more intricate as you go to large scales. It actually gets phenomenally simple and obeys extremely simple laws. And so this new framework we've developed is perfectly compatible with that idea. So here's Lambda CDM.

The lambda means the cosmological constant, which Einstein invented in, I think it was 1917, to explain why the universe wasn't collapsing in the absence of any observations. He invented the lambda. So that's a very old concept. It is the very simplest form of matter, you can imagine. It's completely uniform in space, in time, it's unchanging in time. and we say it's Lorentz invariant. If you move, it doesn't appear to change at all. Lambda CDM is this model with a Lambda.

It has a dark matter called cold dark matter. And with just five numbers, you fit the large-scale structure of the universe. This is a beautiful artist's impression with the solar system in the middle. And as we look outwards, we're also going backwards in time to the emission, the surface which surrounds us, which emitted the cosmic microwave radiation, which we now detect, our best probe of the early universe.

And before that, the blue circle is the Big Bang singularity. So that blue circle really is a point because this picture doesn't really show properly the fact that as you go back in time, the space is shrinking. And that blue circle is this mysterious Big Bang singularity from which everything emerged. So Lambda CDM is this model.

It has just three numbers describe the relative abundances of matter, the different kinds of matter to the radiation. There's a lambda. There's dark matter. We seem to need to explain the clumping of galaxies and how it helped galaxies form. We've got ordinary matter made of atoms and nucleons and electrons,

and so on, so ordinary matter. And then we have the radiation. So there are three numbers telling you how much of these three types of matter there are relative to the radiation, which came out of the Big Bang. And then there are perturbations. So if we look across the sky

at the temperature of the microwave radiation, and we think about that temperature, the temperature variations on different wavelengths across the sky, then the amplitude is about one part 100,000. It's really tiny. So 30 micro-Calvin out of 3 degrees Kelvin. So that's the amplitude, 10 to the minus 5. So the universe is incredibly homogeneous and isotropic. These perturbations are really small, but then they do vary a little bit with wavelength. And this is showing you that they

get slightly stronger, just by 2%. The exponent here is just 2%. As you increase the wavelength, in units of the visible length, the entire visible size of the universe. Better to say if you go to shorter wavelengths, the largest wavelength we can see is LVIS, and if I go to shorter wavelengths, the strength of the variations decreases very slightly due to this tilt. So there are five numbers which are measured, and these are consistent, you know, within errors,

with everything we see. And many parameters that could have been there have so far turned out to be zero. So space curvature, you mentioned the deviations from Gaussianity, the very simplest kind of noise that describes the perturbations. Tensor perturbations, you know, people were very excited a few years ago, claiming to see them. They don't seem to be there. And variations.

This tensor perturbation would be the smoking gun, of inflation. And the fact that it's not there is putting inflation under more and more pressure. And my prediction is that if continues not to be seen and if the experiments increase, you know, in precision as much as they're expected to, then let's say in 10 years time, inflation will be a dead concept. This Lambda CDM model is extremely predictive. Here's the power spectrum of the temperature, these beautiful wiggles. These are just simple physics, the oscillation of plasma waves, sound waves, in this hot plasma that we see all around us in a cosmic micro background.

And, you know, I was very lucky to get into this game when the polarization of the plasma hadn't been predicted theoretically. In fact, some very famous theorists had written a paper saying it should be zero. But we calculate the cross-correlation for the first. time they had claimed there would be no cross correlation but we calculated it and it's this red curve and as you can see the data fits bang on it and the amazing thing is there are no free parameters in the fit if you fit the cosmological parameters to the lower curve the upper curve is just a prediction and it's

spot on the data so this among other things convinces me the universe is extraordinarily simple and it fits with known physics to a astonishing degree. Here's inflation. There are all these different models of inflation. There are hundreds of different models. Here's phi squared. That was one of the simplest models. This is where the current data is. So that looks well ruled out. And as the fraction of the temperature fluctuation due to long wavelength gravitational waves predicted by inflation, as that fraction falls as experiments improve, inflation is under more and more pressure, more and more models are being ruled out. And I think that's becoming accepted that the whole picture of inflation is in

general. This episode is brought to you by Redfin. You're listening to a podcast, which means you're probably multitasking, maybe even scrolling home listings on Redfin, saving homes without expecting to get them. But Redfin isn't just built for endless browsing. It's built to help you find and own a home. With agents who close twice as many deals, when you find the one, you've got a real shot at getting it. Get started at redfin.com. Own the dream. So here is the CPT symmetric universe. CPT, charge conjugation, parity and time reversal, the most basic known symmetry in physics, a consequence of Lorentzian variance,

and this mathematical property of physical laws, which is analyticity. Our hypothesis is just that the universe respects the symmetry, the most basic symmetry of its laws. That's all. How could you do that? Because the universe is full of matter, has an arrow of time.

These seem to violate CPT. Well, the way you do that is by having a mirror universe, in which the mirror is exactly the CPT symmetry. So if I go from one side to the other side, I'm reversing the arrow of time, I'm turning matter into antimatter and also inverting space, but that's a little harder to draw.

Now, what we noticed is that if we study the behavior, this is our universe, the Lambda CDM model, just follow it back to the singularity, the amazing thing that happens is that the size of the universe called A of T or the scale factor is linear in the time at early times. And this turns out, this is not a fluke. This is a fundamental reason behind it. And the reason behind it is that the matter is what we call conformally invariant.

The matter in the universe does not know about the size of the universe. The consequence of this conformal symmetry is that the size of the universe disappears in this very simple way is linear. Because it's linear, you can just extrapolate through t-equal-zero. The metric or the line element is quadratic in a of t. And so this just goes like t-squared and the universe looks the same on both sides. So the standard cosmology is CPT symmetric. And our proposal is that we adopt that. as a basic principle.

Does that hold even beneath the plank scale? That's our hypothesis, okay? Now, no one has a theory of quantum gravity. So we don't know how to reconcile quantum mechanics with gravity theoretically. We have various approaches, which seem to work to some degree. The best, well, the most useful approach, in my opinion so far is the path integral approach.

where basically you start with some universe, a three geometry, so some kind of configuration, three-dimensional configuration of gravity and matter, and then you evolve it into another three configuration. And actually this was John Wheeler's picture of quantum gravity. He had an initial three geometry, a final three geometry, and then the prescription for quantum gravity is that you summed over all possible for geometries or space times connecting those to three geometries. So we can actually do this at some level.

We can do these path integrals. There are issues about divergences and renormalization and all kinds of tricky points to deal with, which have not been satisfactorily resolved. But at a certain level, you know, one can make sense of this. And certainly in a semi-classical approximation to quantum gravity, the first thing you have to do is find a classical solution, which respects the boundary conditions.

So our prescription is that the initial universe, if you like, the initial three geometry and the final three geometry are identical. That's what CPT symmetry means. And so the universe before the bang, long before the bang, was literally a mirror image of our universe. Our claim is that the right boundary condition at the Big Bang is actually a CPT symmetric boundary condition. And the way to implement it is to use the method of images. You have your universe.

After the Bang, you make an identical copy before the Bang, and then you do the path integral between these two universes. So, you know, there are fluctuations here when you sum over paths. this Big Bang point could be nearer one side or the other. That's what quantum fluctuations do. But what we're not doing is kind of injecting a universe at the Big Bang, which is the picture most people have in mind for cosmology, and that's what inflationary cosmology sort of has in mind,

that somebody injected a universe at the plank time. We don't have that picture at all, and I think that picture is actually ridiculous, because the worst possible place to define the initial conditions of the universe is nearer singularity because that's where the quantum fluctuations are huge, and you really don't have any sort of classical picture of what's going on. To me, it makes much more sense to define initial conditions in this kind of mirror way. But, you know, I have to admit that we are hoping that the laws of quantum gravity,

when they are understood, will be consistent with this way of defining the initial condition of the universe. So your model has to not only produce scalar perturbations, but has to suppress tensor perturbations. Can we understand that? So once you have a well-defined boundary condition on the universe, you can actually calculate the number of states for cosmologies with different parameters, different spatial curvature, matter content, radiation, lambda. You can vary all the cosmological parameters. The three numbers I gave you on the first slide

and spatial curvature as well. And you can count how many states there are for a universe. In an extremely clever calculation that Stephen Hawking did of the entropy of a black hole, we managed to generalize this to the entropy of a universe. We could count the states. And lo and behold, we found that the universes with the most states are spatially flat, homogeneous and isotropic,

and have a small positive cosmological constant. Okay? Now, your question, so basically, this boundary condition allows you to give a well-defined answer to what we call the measure on the initial conditions for the universe. And that measure turns out to predict the universe just like ours. So all of the claims of inflation, that this dynamical mechanism would smooth and flatten the universe turns out to be unnecessary.

You don't need that. Just use thermodynamics, and thermodynamics, just like the gas in a room, is homogeneous and isotropic, because that's where most of the states are. It's a typical state of atoms in the room is homogeneous and isotropic, and that's why gas is almost uniform.

While the same argument works for the universe, and amazingly, it explains spatial, flatness as well. Now, to get to your questions about the perturbations, I have to, I'm afraid, get a little bit more technical. We should look at this picture. So I've obscured it with these graphs, I'm afraid, but we should stare at this picture and try to interpret it in the minimal possible way. What is it telling us? Because it's certainly very fundamental. These are the primordial structures in the universe. And they're very large scale, right? They're separated by scales which haven't communicated with each other since the Big Bang. So this is really a very

fundamental and important feature of the universe. Where did those fluctuations come from? Now, so what we did, very unconventional, we said, okay, let's believe these observations are truly primordial. What are they telling us? What kind of field, what kind of quantum field would have fluctuations with exactly this spectrum? Okay. So it turns out when you ask that question, the answer is actually very clear. When you do quantum field theory, you start from an action principle. Typically, we start from an action principle. And usually we start from an action with two derivatives so that the equations of motion are second order in time, just like Newton's equations, F-Equels M-A, involve two derivatives. And there are various reasons why classical physics

has always only used equations with two-time derivatives. Okay? Equations with two-time derivatives do not give you the pattern of quantum fluctuations we see on the sky. The pattern we see is given to you by a field with four time derivatives in the action, and four time derivatives in its equations of motion. So this box here, minus D by DT squared plus grad squared, right? So four-dimensional second-order operator, and you see it occurs squared in the action. So the equation of motion for phi is four derivatives.

It turns out this theory, and it's really dimensional analysis, the two-point function in this theory is scale and number. variant. It has same numbers of k in the numerator as the denominator. And the reason for that is, you see, if you look at this action, there are four xes here in the d4x, and there are four inverse xes in these operators, this delimbersion square, there are four powers of x in the denominator. That means that this field phi is dimensionless, and that's what we call a dimension zero field. And because it's dimension zero, its two-point function hasn't got any scale in it. And so, you know, you can't have K appearing differently in the top and the bottom in this formula.

So basically, a dimension zero field gives scale invariant fluctuations. And what we've shown in recent work is this kind of field not only explains the spectrum naively, just, you know, that's why we chose this field. It actually gets the amplitude right, and it gets the tilt, the 2% tilt right, without any free parameters. It is way better than inflation. In inflation, you always dialed a model to fit the observations. It turned out we didn't need to. But I have to tell you a little bit more about it in order to explain how that works.

Guided by the observations, we got very interested in these four derivative fields. Do they make sense? Are they mathematically consistent? Can we make sense of the quantum theory? And actually, we're still working very hard on this. These are rather non-trivial questions, but we have some super exciting new results indicating that these fields should give rise to the Higgs boson,

something like a Higgs boson, and they will solve the hierarchy problem. The problem for why the weak scale is so different than the Planck scale. But the way we were led, I emphasize this, the way we were led to this theory is by looking at the sky and being naive. It's as simple as that. Okay, now, where did it lead us? So we say, say we have these fields, these funny four-derivative fields, what do they do for you? Now, to describe the Big Bang singularity, I need this conformal symmetry.

I need to make sure that the matter does not. not know about the size of the universe because the universe is shrinking away. There is a sort of mathematical way of describing that, which is called the conformal anomaly. Even if I write down a theory like Maxwell's theory for electromagnetism or Dirac's theory of the electron, both of which are conformally symmetric. So neither of them know what the size of the universe is. Their equations are independent of the size of the universe, classically. But when you quantum, it, you get this funny thing called a conformal anomaly. And these are been calculated ever since the 70s.

There are actually two of them. And if you calculate them in quantum field theory, they turn out to be proportional to a set of integers, right? With funny coefficients. So these are unfortunately very technical calculations, but you can work out precisely what is the anomaly. What are the anomalies in this conformal symmetry? The first thing we noticed is these funny dimension zero fields come in with minor signs.

And that's good because these ends here are counting the number of scalers, of ordinary scalers, two derivative scalers, the number of fermions, the number of gauge bosons. They all contribute positively. So there's no way of canceling the conformal anomaly. But when you introduce these dimension zero guys, you can. Okay, with some particular numbers. A very long-standing problem in quantum field theory and coupling it to gravity is the vacuum energy. The vacuum energy in quantum field theory is generically infinite, okay? Because all the waves in the theory are quantized and they have zero point fluctuations,

and if you add them up, you get infinite energy. And so the scalar bosons like the Higgs boson contribute positively, fermions contribute negatively, gauge bosons positively. The two here is just the number of degrees of freedom. And our dimension zero-scalers also contribute positively. So you see we have three kind of puzzles in coupling quantum fields to gravity.

And they all depend on a set of integers. So we said, is it possible that they cancel? Is it possible to cancel them? At least we have some minor signs. Maybe they cancel. The first thing had happened is that if you, So just write down the sum of integers with these coefficients and set them zero. All three zero.

You've got three equations for four unknowns, but these numbers have to be integers, right? So typically in linear equations, you'll always get a solution, but it may be fractional or it may not be an integer. So vanishing of all three of these equations immediately implies that there are no fundamental scalers. There is no inflatom. There can't be a phytton. fundamental Higgs boson. If you're going to have a Higgs boson, it must be built out of these guys, the dimension zero guys, which is possible. The Higgs must be composite and it must be made of these guys. So that's a sort of negative conclusion, right? We've gone back. We've explained

that the Higgs is a composite object, not a fundamental particle. Now, how is that received? because, I mean, there seem to be obsessions, well, being a fundamental particle, yeah. Yeah, I think string theory tends to assume it is fundamental. People who think maybe, I hesitate to say more deeply, but people who come more from a bottom-up perspective have always worried about the hierarchy problem, the fact that the Higgs boson, when you introduce the Higgs field into the standard model, you put in a mass for it. and that's just inserted by hand,

and that mass is way below the plank mass by factor of 10 to the 17. And so that's a huge fine-tuning problem. Now, people, particle physicists, bottom-up particle physicist for a while, have realized that small mass parameters can occur very naturally in quantum field theories due to renormalization. So, for example, in QCD, the theory of nuclei, atomic nuclei, the mass of a nucleon is one GV. It's much less than the blank mass. But in that case, it's completely natural.

Why? Because the strong interactions are what are called asymptotically free. That at high energies, plank energy, the coupling is small, maybe one-tenth, or actually it's about a 20th. And then if you go down to low energies, the coupling gets stronger. And so when you hit a certain energy, the coupling becomes so strong that the excitations in the theory become bound. The gluons become bound as glue balls. And their mass is way lower.

So you start off with a coupling of, say, 120th at the plank scale. you go down to low energies to where the coupling becomes strong. Because the coupling only runs logarithmically with energy, the mass scale where it's strong is exponentially smaller than the scale where you define the coupling, the plank mass. And so in this way, you naturally explain why nucleon masses are so much less than the plank mass without any fine-tuning.

It's just because the coupling runs logarithmically. So it turns out that for these dimension zero scalers, there's the same phenomenon, that they are weakly coupled, they're asymptotically free, they're weakly coupled at the plank scale, you run them down, they become strongly coupled, and then this condensate can occur at the weak scale, and that would explain why the weak mass is so much less than the plank mass. And we're not the first to realize that a logarithmic running coupling of the Higgs,

would explain the hierarchy problem without any need for supersymmetry or any other paraphernalia. Excema is unpredictable, but you can flare less with ebbglis, a once-monthly treatment for moderate-tissaphyr, after an initial four-month-month-longer dosing phase, about four-and-10 people taking ebb-glis,

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can occur that can be severe. Eye problems can occur. Tell your doctor if you have new or worsening eye problems. You should not receive a live vaccine when treated with Epglis. Before starting Epgless, tell your doctor if you have a parasitic infection. Ask your doctor about Epglois and visit ebbgless.lis.lid.com or call 1800 LilyRx or 1-800 545-979. Now here's the stunning prediction. Set NS1 to zero and take any two of the remaining equations and they, so just use one of them to eliminate NS0, right, and plug it into the other one, and you'll get an equation that the number of fermion degrees of freedom equals four times the number of gauge boson degrees of freedom.

So in the standard model, there are 12 gauge bosons. There are eight gluons. It's the dimension of SU3, three weak bosons, dimension of SU2, and the U1, which is the hypercharge gauge boson. So there are 12 gauge bosons in the standard model. 12 times 4 is 48. We predict there are 48 fermions. you get 48 fermions only if you have three fomion generations each with the right-handed neutrino.

So, as far as I know, this is easily the simplest explanation for why there are three fermion generations in the standard model, and it's really rigid. Okay, so if you try to generalize this to SU5 or S-O-10 or any other Grand Unified theory, it doesn't work. Actually, it does work for a few cases, but they're very sporadic. So this is quite a coincidence. And when we're We saw this, we said, wait a second, we started out trying to fit fluctuations in the cosmos, and we ended up explaining why they're three fomion generations. So when I've solved these equations for, so I input the number of gauge bosons, 12, I have to have 48 fomions, and then these equations tell me how many of these dimensions

zero scalers you have, and they have to be 36. So there are 36 of these guys. Why the hell 36? This is only a hint, but it turns out that the symmetry on phase four-dimensional Lorentzian phase space, coordinates and mementa, there's a symmetry which acts on this eight quantities, the four spacetime coordinates and the four mementa. There's a symmetry there, which is a unitary symplectic group of four dimensions. It has dimension 36.

We haven't written any papers about this, but I think this is a hint that maybe, by the way, this cannot be made into a grand unified theory. It's more like twister theory, which Roger Penrose has pushed with considerable success. But what this would be is a sort of double twister theory. If he does with space time, the X's, if we generalize, extend that to the momenta, in other words, work on face base, it looks like. like we're going to get a generalization of twister theory. And by the way, this 36 scalers sounds weird, but in twister calculations, just in the last two, three years,

people have, is a mathematician called Kevin Costello at Perimeter Institute, who's shown that twister path integrals only work. They're only anomaly free if you introduce dimension zero scalers, just like these ones. And this anomaly cancellation mechanism we have here is echoed in twister path integrals. So that's really fascinating.

And the reason it's so fascinating is, you know, the arguments I've given here are strictly lowest order. These are free fields with no interactions in a curved background. So it's the crudest calculation you can do. His calculations are valid to all orders. and they show that this anomaly cancellation works to all orders. So there's kind of an amazing set of mathematics emerging. I think what's kind of going on is that we are building, I hope we are,

we are building a four-dimensional version of string theory, which is minimal. You know, this principle of conformal symmetry is exactly the principle people use in string theory, but they use it in two dimensions for the string world sheet. we're using it for four-dimensional space time. We're making use of the ideas and the technology that were developed in string theory,

but we're seeing that it can work in a far more minimal way than string theory. And then maybe in the last couple of minutes before I need to take off, yeah, we could go over the budget and also the predictions and the scorecard with respect to plank, and then we'll have to do a part two because there's so much more to cover. This is the surprise. Now, a lot is buried under this phrase, some technical assumptions, okay?

And it would take a lot to explain those. But again, we've tried to be as minimal and precise as possible. And what we do is we calculate what would these 36 dimension zero scalers, how would they actually appear in the cosmic micro background? How would they distort the cosmic microwave background? So we've done an honest calculation as carefully as we could. There's still lots of technical assumptions within it, but we have not cheated in the answer.

We've not adjusted anything. We've literally tried to be as minimal as we could. And we computed from first principles, what's the power spectrum of what's called the co-moving curvature. It's just a parameterization of the, density fluctuations in the primordial universe. And what we found is, so lots of numbers come in like pies and fives and things like that, the C here is to do with the couplings in the standard model, running couplings.

And basically the principle we've adopted is this conformal symmetry. We use these dimension zero scalers to cancel the scale dependence of the running couplings in the standard model. And we have to do that to get conformal symmetry. Turns out when you do that, all the numbers get fixed. These numbers are the, you know, this one, these are the coupling constants of the strong, weak, SU3, SU2, and U1 gauge forces.

So these numbers are exactly predicted by the standard model with three generations, et cetera. So we get a number here, and then we get a tilt. And the tilt depends on the strong coupling constant, alpha 3. And it just so happens that the strong coupling constant extrapolated the plank scale, and then including this factor, which we derive, gives exactly the observed tilt. Okay, so the, we predict the tilt of, well, it's usually the scalar index minus, I think 1 minus ns is usually called the tilt, and so that's about 0.04 in the power

spectrum. So that's what our prediction is. And this is what Plank gives. So we're off by a factor of two in the amplitude, but we're spot on in this index. So actually, this was totally amazing because we didn't dial anything. And this a priori, this amplitude could have been off by many, many orders of magnitude. So to be within a factor of two is pretty amazing. What are the next steps, Neil? Where do we go from here to, is it data? Yeah, so in principle data, but in practice, we have to cross the T's and dot the eyes on the theory. We have to show that this really is mathematically consistent. These four derivative theories, four derivative scalar theories like this one,

are well known to sort of suffer from diseases called ghosts and classical instabilities and all kinds of other phenomena. We've been very busy trying to show or to understand whether these theories actually avoid those problems. And I'm really excited because I think we have conclusively shown that there are no such problems with this theory. But we'll have to fight our theoretical battles with all the theorists who claimed they were these problems. The crucial work now is really to get the theory on absolutely mathematically sound footing. but if we can do that, then here we have a very precise formula

that the running of this strong interaction coupling determines the tilt in the spectrum of the CMB. So what we're saying here, because this alpha-3 runs so slowly with wave number at long wavelengths, we predict that there is no running of the spectral index in the CMB. We predict that that that's...

should be effectively zero. Yeah, in principle, you know, as LHC goes to higher energy and measures the measures these couplings in the standard model, all of these more and more precisely, and then, of course, theorists have to calculate to higher and higher loop order, but in principle, there could be an extremely precise test. And I think about this as follows, that, you know, we're sitting here looking back at the Big Bang. The Big Bang is the most powerful accelerator we know. And it could be that these fluctuations are actually telling us the laws of particle physics at the plank scale, at the blank energy. Our hypothesis is that there's nothing really in between these scales. We have to, of course, include these right-handed neutrinos and so on and so

forth. So these will slightly alter the results. But other than those, there's nothing beyond the standard model. And so it could be that as our experiments get more and more precise, as our theoretical calculations get more and more precise, we really will see all the way back to the plank time. And that, you know, that's a wonderful, wonderful prospect. Love to travel forward in time to see how it all turns out. I'm a little worried. What if I get there and I find out? I should have stayed home in 2025, but Neil Turrock, this has been fascinating as it always is with you. I just want to thank you so much for sharing your time. And I do want to talk about the

black hole implications and further implications, and especially as we come online, with our first like data from the Simon's Observatory. It's going to be a very exciting next couple of years for cosmology on theoretical and on experimental side. So Neil, thank you so much for coming back on and I'm not to get you back for a part three. Definitely. Thanks a lot. Thank you. Everybody, I'm so excited that you made it all the way to the end. You're still listening to this. It's me, your favorite host, Into the Impossible. And I'm asking you, my iOS possessing listeners. I love you so much compared to those Android heathens out there or those Spotify. by dwellers.

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