Adam Brown

Yeah, so there are two components to that question.

You have an intuition that if something is real, it needs to be spatially localized and things that are delocalized in space somehow can't be real.

I would say that that's not my intuition.

My intuition is that there can be two completely different descriptions of the same physics.

And if it's precise, neither of those is any more real than the other.

Things do not need to be spatially localized.

You separately asked, what would it look like?

What would a version of...

Where is the boundary theory in de Sutter space, since there's no boundary?

That is a great question that people who are trying to generalize ADS CFT to a universe like ours that has a positive squash model constant, that they wrestle with.

And there's more than one proposal, some of which is that the place... One example of a proposal is that the dual theory should live on the cosmic horizon.

So there's a... If you go...

five billion light years you can send information to that that point and have it returned to you but on the other hand there are things that are 100 billion light years away that we'll never be able to communicate with and there's a boundary between those two between some things that we could in principle communicate with and things that we couldn't in principle communicate with that is the cosmological horizon and some people who are trying to do

A version of holography that works in universes of the positive cosmological constant like to put the second theory there.

Other people like to put it in the distant future, in the sort of infinitely distant future.

And that's part of the problem is that where do you even put that theory?

It's not like in our universe where you can just put it spatially infinitely far away and be done with it.

Absolutely.

So a cosmological horizon is very different from a black hole horizon in this regard.

A black hole horizon, there is a point of no return.