f*******d
发帖数: 339 | 1 I often heard about anti-deSitter Universe. I know what is a de Sitter Universe,
which is explained in many cosmology books. Basically, it is a vacuum energy
dominated Universe. However, I don't know what is an Anti-de Sitter Universe.
It must be the opposite of the de Sitter space, but in what sense? A Universe
dominated by negative vacuum energy? Could any string theorist explain it to
me? | h***u
发帖数: 25 | 2 First of all, I don't think the AdS/CFT is a theory of the Universe.
But we can use the GR and SuperGravity(SUGRA) on any kind of Einstein
maniford.
AdS can be discribed by
-X_{-1}^2-X_0^2+X_i X^i=0 in a D+1 Euclidean space( with 2 time directions
and D-1 space directions). The metric of it can be induced from the flat
metric of R^{D-1,2}.
AdS/CFT correspondence said, The String theory (or is low energy limit: SUGRA)
is correlate to some CFT on the "boundary" of the AdS.
Although there is no pro
【在 f*******d 的大作中提到】
: I often heard about anti-deSitter Universe. I know what is a de Sitter Universe,
: which is explained in many cosmology books. Basically, it is a vacuum energy
: dominated Universe. However, I don't know what is an Anti-de Sitter Universe.
: It must be the opposite of the de Sitter space, but in what sense? A Universe
: dominated by negative vacuum energy? Could any string theorist explain it to
: me?
| f*******d
发帖数: 339 | 3 Thanks, now I see what is AdS. However, there are two points I
don't understand:
1. Why is another negative signature (time-like) dimension
introduced in string theory? Is there any motivation for this?
2. You said it is impossible to understand QCD at high energies
from traditional (perturbative) point of view. Is that an
typo? I though QCD has asymptotic freedom, so it should be easy
to understand at high energy. It is the low energy limit that
is difficult to understand perturbatively. | h***u
发帖数: 25 | 4
1. There is just one negative signature in AdS space! you ca try to
calculate the metrix of it. ( I made a mistake in the equation, the right
side of the equation should be R^2, R is like the radium of a ball).
2. I made another mistake here, should be strong interaction
limit( low energy).
【在 f*******d 的大作中提到】
: Thanks, now I see what is AdS. However, there are two points I
: don't understand:
: 1. Why is another negative signature (time-like) dimension
: introduced in string theory? Is there any motivation for this?
: 2. You said it is impossible to understand QCD at high energies
: from traditional (perturbative) point of view. Is that an
: typo? I though QCD has asymptotic freedom, so it should be easy
: to understand at high energy. It is the low energy limit that
: is difficult to understand perturbatively.
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