𝕁onas 🐈🐘

@dgb37 I'm just saying it's an analogy. The tttc uses p.e.r.s internal to an indexed poset. But not over a "fixed" set in any sense I would say. @jonmsterling @MartinEscardo @zwarich

@dgb37 haha, sounds like you rediscovered the tripos-to-topos construction! That one uses partial equivalence relations and functional relations between them. @jonmsterling @MartinEscardo @zwarich

@jonmsterling What are the three notions of setoids that you have in mind? I've come across the word many times, and was never quite sure what people meant by it. @MartinEscardo @zwarich

@johncarlosbaez@mathstodon.xyz

the universe fits the profile of a white hole a lot better than of a black hole.

Yes, because of the singularity in the past ? But if there also was a singularity in the future then it could be a black hole ?

@johncarlosbaez@mathstodon.xyz So it the picture wrong or am I misinterpreting it ? Maybe the Hubble radius dot is close to the "black hole line", but not quite on it ? Would a universe with a big-cruch singularity in the future (that people used to believe in) be a black hole ? Or does the line capture the correct notion of black hole only for not-too-large objects ? Or is it about universe vs observable universe ? (I have watched the video and remember the discussion of white holes, but my understanding of all this is superficial)

@dougmerritt@mathstodon.xyz @johncarlosbaez@mathstodon.xyz on the other hand, the whole universe is a black hole! (The Hubble radius dot in the graphic)