Anti-de Sitter AdSn may be defined by the quadric
−(x0)2−(x1)2+→x2=−α2
embedded in
R2,n−1, where I write
→x2 as the squared norm
|→x|2 of
→x=(x2,…,xn). Now, I don't quite understand how is it justified that the topology of this space is
S1×Rn−1. As I understand it informally, I could write
(1) as
(x0)2+(x1)2=α2+→x2
and then fix the
(n−1) terms
→x2, each one on
R, such that
(2) defines a circle
S1.
This is actually a reasoning I came up to later, based on the case of dSn (in which one just fixes the time variable) and when I saw what the topology was meant to be, but actually I first wrote (1) as
→x2=(x0)2+(x1)2−α2
which for fixed
x0,x1, both in
R, defines a sphere
Sn−2, so the topology would be something like
Sn−2×R2, (which is indeed similar to that of
dSn) right? I even liked this one better, since I could relate it as the 2 temporal dimensions on
R2 and the spatial ones on
Sn−2.
I don't *really* know topology, so I would like to know what is going on even if it's pretty basic and how could I interpret topological differences physically.
**Update**: I originally used ⊗ instead of × in the question. My reference to do this is page 4 of [Ingemar Bengtsson's notes on Anti-de Sitter space][1]; so is that simply a *typo* in the notes?
**Update 2**: I'm trying to understand this thing in simpler terms. If I write Minkowski 4-dimensional space in spherical coordinates, could I say that it's topology is R×S3? If so, how come?
[1]: http://www.fysik.su.se/~ingemar/Kurs.pdf
This post imported from StackExchange Physics at 2014-05-04 11:13 (UCT), posted by SE-user Pedro Figueroa