Shawn Ryan

This is what you're doing right now, right?

Yeah, I know.

So yeah, a lot of, I think, some British twister people have some fun sense of humor of how they name things as far as celestial sphere and the heavenly equations.

I think there's fun things.

So celestial sphere literally is night sky stars.

If you're like Millennium Falcon or whatever and you're accelerating, you might imagine that like you'll see the distribution of the stars in the night sky move around a bit.

So like they're going to dilate.

And so that's somehow seeing that there's like the boost symmetry of the space-time is a dilatation of this sphere.

So what we're doing is trying to map all of the observables that we want to have to this night sky times a null direction that's complicated to do.

So we just project it back down to the night sky.

And the reason why we do it is, again, because we're just copying and pasting and then generalizing things that have worked before.

both someone like Hawking thinking about putting quantum field theory in a black hole or someone who's like a string theorist who's saying there's like 10 dimensions or 11 dimensions and I'm gonna like have all these all this extra field content that I then have to like have this extra dimension like wrapped up and be tiny and never see it but both of those types of frameworks end up leading to this cute notion that somehow the easiest way to get around describing a quantum gravity system is to find an equivalent non-gravitational system that it's dual to

And so from the Hawking point of view, it's like there's a sense in which this black hole behaves like a thermal system where the entropy is this area law.

And so, okay, there's this fun kind of almost information theoretic vibe to like how like gravitational solutions.

Then from the string theory side, there's this kind of more complicated, like some theory on brains backreacting, where you have a more precise actual equivalence between, I know some very esoteric, like bulk strings on like some gravitational space time.

That's the wrong cosmological constant, wrong number of dimensions, yada, yada.

But it's equivalent to another gauge theory that I know.

And so a lot of people in my field love like those precise dualities.

because then they have power on both sides.

Maybe some things are easy to compute as a geometric object and other things are easier to compute on the other side.