All Questions
3
questions
3
votes
1
answer
735
views
How many null directions are there?
The metric signature of spacetime is usually given as ($3,1$), but spaces can also be ($3,n,1$). Null surfaces include photons and event horizons, which exist, so is $n$ actually $ > 1$ in the ...
5
votes
1
answer
221
views
Black rings in 4D gravity
In Introduction to Black Hole Physics by Valeri P. Frolov, Andrei Zelnikov there is a discussion of gravity solutions. They present some examples of solutions with non-spherical horizon topology:
But ...
- 5,717
5
votes
2
answers
5k
views
A two-dimensional event horizon?
Today, I came across an article which says that the Universe began with the collapse of a 4-dimensional [spatial] Universe. Well, I don't know if there's any way to confirm these like it is with all ...
- 1,804