Shawn Ryan

But instead I was like, oh, by the way, there are experiments that are maybe changing our opinions a little bit or calling the question some notions of those parameters that describe this thing.

So that's the thing.

So the fun thing about cosmology, if you're doing like a holography for like deciduous space times, is there is like a literal horizon where you can, like as one observer, you're not seeing the whole thing.

And so the world that I live in is like kind of understanding the mathematical structure you can attach to the kind of the boundaries of the space time.

And in most situations, like in the...

ADS context, which is this like wrong sign, cosmological constant version toy model, or in the case where I do, like it's really the space-time boundary and not the boundary of some observer.

And then you have to deal with observers and the sitter is hard for lots of reasons.

So I just go, ah.

No, it doesn't.

You're absolutely right.

In the sitter, you're basically propagating a wave on a curved background versus a flat background, and it changes the form of it further away.

People have papers trying to talk about it, like memory on the observer horizon in the sitter, which is the closest thing.

But the thing that's relevant is you want to think about what scale is that important as compared to what scale I'm seeing the wave coming from this inspiring binary system.

And so, at least for example, a lot of things I do are also relevant to, not the memory effects so much, but these asymptotic symmetry stories can be applied to amplitudes.

And there, what you're doing, you have CERN, you have this collider, and it's such a small scale where these things are interacting that the detector itself is considered to be at infinity.

But it's not infinite.

I mean, it's huge, but that's hardly infinity.

And so, can I pretend or ignore that expansion for some things?

Sometimes yes, and then sometimes no.

Uh-oh.