A Black Hole Is Not a Dead Star

追加: 2026-05-12

[00:00:00]Okay, let me be non-concrete. Let's imagine you had a black hole gun. So, not a ray gun, just a tiny microscopic black hole gun. What do you think would happen in your Klein model if you shot a black hole to one of these small dimensions? Does anything interesting happen?

[00:00:14]Um, I wish I could say it's a simple thing to calculate cuz even the black hole metric I have to rethink in the Klein bottle. Cuz the black hole metric that we're accustomed to doing it has an asymptotically flat space at infinity.

[00:00:31]And so I a lot of people have done black holes in higher dimensional spaces. It's they can be tricky. It it's not completely you know, it's not just a given like a marble. I threw a marble in the space. So, I'd have to first of all see It's not a muffin.

[00:00:44]It's not a It's not a muffin recipe.

[00:00:47]Um, not throwing a muffin in there. Um, so can I make a 3D Is it a 3D black hole? Is it a 5D black hole?

[00:00:55]Um, does it have an event horizon in all five directions?

[00:01:00]Or does it only have an event horizon in three? Like, I'm already like, oh, I got a I got a lot I have to think about.

[00:01:06]So, um, but it sounds like an interesting thing to try.

[00:01:10]>> [laughter] >> Even though black holes are extremely complicated, they're they're quite simple in many respects. They're characterized by just a couple numbers like mass and charge and spin. So, also particles are characterized by just a few quantum numbers. So, do you think black holes should appear on the particle spectrum? And then if not, then where does this analogy break down? It's a great question. I absolutely do think they should. I think black holes being an interesting terrain on which to understand quantum gravity or the information loss paradox is not just a coincidence. It's because there's something fundamental about black holes.

[00:01:46]They are somehow, I believe, part of the original ingredients of the universe.

[00:01:52]And um, and I think exactly what you said is true that I I know that What does it mean to be an electron? It means exactly its quantum numbers. Its charge, its mass, its spin, whatever list you want to add to that to make it an electron.

[00:02:05]And that's the only thing an electron is. It's not there It has no other detail than that. You cannot say, "Oh, the electron in my body is somehow different than the electron in an asteroid." Okay?

[00:02:19]They're interchangeable.

[00:02:22]And that interchangeability is what we expect of a fundamental particle.

[00:02:26]And it's very odd that black holes have that property as well. Now, they they can have a whole continuum of masses and spins and electric charges.

[00:02:37]So, that might seem a little different, but really the fact that every single black hole with a given set of numbers, charge, mass, spin, is indistinguishable by the definition of the event horizon. It has no features. It can have no hair. That's the statement it can have no hair. No details about the interior of that black hole can be expressed except its charge, mass, and spin. And that makes them feel like fundamental particles.

[00:03:03]Um and so, I think black holes were already telling us something about themselves even when we looked at pure relativity, cuz that's a result from pure relativity that they are featureless. They're timeless and they're featureless. If I turn off quantum mechanics and Hawking radiation, I just think about general relativity.

[00:03:21]They do not age.

[00:03:24]They are utterly timeless in the same way an electron is utterly timeless.

[00:03:28]Now, they can get heavier, that's true.

[00:03:30]There are pro- processes. But left to its own devices, there's no clock.

[00:03:34]There's no watching that thing and saying, "What's happening? How long has it been there? Or is it different than this one? This one was formed by a star, and this one was formed by uh you know, crushing donkeys together." Like, there's no way you can tell these details about it. Um and so, I think that it was reasonable to suspect that in the early universe a primordial black hole would form or or you know, a spectrum of primordial black holes will form in the early universe. I think that's completely reasonable to expect that. That there stars a black hole is not a dead star. A dead star is just a way nature figured out how to make a black hole.

[00:04:10]Um, but there are other ways to make a black hole. Maybe a accelerator experiments, maybe particles crashing together naturally at high energies, maybe the Big Bang.

[00:04:22]Um, yeah.

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[00:05:04]kurtjaimungal.org.

[00:05:07]Is there something more to this analogy because I imagine that the there are two disanalogies that occur. One is that for a particle, you want there to be a field that corresponds like an electron or a Dirac field or what have you.

[00:05:20]There's no, as far as I know, a black hole field that creates or annihilates black holes. And then second, that black holes have extreme entropy.

[00:05:28]So, it's like they have some micro structure, they have something else going on. Mhm. And particles, as far as we know, don't. So, do you see those as insurmountable or what?

[00:05:39]No, I think that all I think both of those things is what marches us towards the information loss paradox. Right, it's precisely it's entropy that is reflected by its temperature and and it's because it's hot that it's emitting particles, right? We can think of it that way. And so it's already was marching us towards something, right?

[00:06:00]Marching us towards the information loss crisis.

[00:06:04]But it doesn't seem like the answer is, "Oh, it's just made of of a of a bunch of stuff on the inside and that stuff eventually comes out." Right? So, I think it's saying something really strange about thermodynamics.

[00:06:18]And really strange about gravity being fundamental. I would be less surprised if you told me gravity is not fundamental and that's why there's no fundamental field.

[00:06:30]And that's why the the black hole is not an excitation about a fundamental field.

[00:06:34]Um it's because uh it's only quantum mechanics.

[00:06:39]Interesting. Now, there are some people, some of your colleagues I'm sure, who don't believe gravity's fundamental.

[00:06:45]Yeah, I think a lot of these people know. Yeah, so what are your conversations with them like?

[00:06:50]Um I think well, I guess I I think a person to think about and to look to is somebody like Ted Jacobson, who was doing extremely interesting work about thermodynamics of black holes. And who I if unless I'm projecting or misinterpreting, very early on, uh was saying things like, "Maybe it's not fundamental."

[00:07:14]I mean, after all, whenever you're in a thermodynamic situation, you better start to suspect that you're looking at lots of things and not a fundamental property, right?

[00:07:24]Like, the temperature in this room is an emergent property of a collective of a bunch of molecules moving around.

[00:07:34]Um but if I look deeper and deeper, I'll never find a quantity called temperature. Yes. I'll just never find that quantity.

[00:07:41]Um and I think he was thinking about that because of black hole entropy and the laws of black hole thermodynamics very early on.

[00:07:51]Um, and in a way I think a lot of the attempts to beat black holes into submission and get them to give up their information has kind of brought people a long way around to start to say, oh yeah, maybe it's really just quantum mechanics all the way down.

[00:08:14]And again going back to ADSCFT, which I am not an expert to be clear. I never written a paper in ADSCFT. But just to say again, that seems to say, look, I can describe the entire universe just in terms of quantum field theory with no gravity whatsoever. None.

[00:08:30]And that is an equivalent dictionary to the on the boundary to the universe in the box with gravity. So gravity in that's in at least there it seems to say, well then I could just talk about only quantum fields and there's no gravity.

[00:08:44]And I have a complete description if it holds up, right?

[00:08:49]Um, I think this is exactly where it's all going.

[00:08:54]But we just haven't figured out how to exactly do it yet.

[00:08:59]>> [gasps] >> You know, I just haven't figured out how to start with pure quantum mechanics.

[00:09:04]Like let's say I take ER=EPR really seriously and I think look, fundamentally it's only wormholes and wormholes with entanglement and uh, making bridges that feel like out of out of causal, you know, acausally separated space-time separations that and I just imagine using these as like threads. I can only give my analogy. So I it's like you sew all of these threads, all these quantum entangled wormholes.

[00:09:38]And from a distance, those threads begin to look like a smooth and continuous space-time that has an event horizon.

[00:09:46]Right. It's like embroidery. And from a great distance, it resolves into the smooth event horizon that behaves exactly as general relativity dictates.

[00:09:55]But on closer inspection, there is no general relativity. There's no space-time. There's only the quantum threads, the the embroidery, the threads out of which you embroidered this illusion of a continuous space-time.

[00:10:10]I think that that is very possible that that's how this whole thing plays out.

[00:10:14]And that's why they're acting like fundamental particles, but they're acting like they have microstates.

[00:10:19]Um Hm. Their microstates are maybe these these ER equals EPR things.