481 research outputs found
Dilaton test of connection between AdS_3 X S^3 and 5D black hole
A 5D black hole(M) is investigated in the type IIB superstring theory
compactified on ST. This corresponds to AdSST in the near horizon with asymptotically flat space. Here the
harmonic gauge is introduced to decouple the mixing between the dilaton and
others. On the other hand we obtain the BTZ balck
hole(AdSST) as the non-dilatonic solution. We calculate
the greybody factor of the dilaton as a test scalar both for a 5D black
hole(MST) and the BTZ black hole(AdSST). The result of the BTZ black hole agrees with the greybody
factor of the dilaton in the dilute gas approximation of a 5D black hole.Comment: revised version to appear in classical and quantum gravity, 15 pages
with RevTe
Cosmological constraints from Gauss-Bonnet braneworld with large-field potentials
We calculate the spectral index and tensor-to-scalar ratio for patch
inflation defined by and ,
using the slow-roll expansion. The patch cosmology arisen from the Gauss-Bonnet
braneworld consists of Gauss-Bonnet (GB), Randall-Sundrum (RS), and 4D general
relativistic (GR) cosmological models. In this work, we choose large-field
potentials of to compare with the observational data. Since
second-order corrections are rather small in the slow-roll limit, the
leading-order calculation is sufficient to compare with the data. Finally, we
show that it is easier to discriminate between quadratic potential and quartic
potential in the GB cosmological model rather than the GR or RS cosmological
models.Comment: 13 pages, title changed, version to appear in JCA
No absorption in de Sitter space
We study the wave equation for a minimally coupled massive scalar in
D-dimensional de Sitter space. We compute the absorption cross section to
investigate its cosmological horizon in the southern diamond. By analogy of the
quantum mechanics, it is found that there is no absorption in de Sitter space.
This means that de Sitter space is usually in thermal equilibrium, like the
black hole in anti de Sitter space. It confirms that the cosmological horizon
not only emits radiation but also absorbs that previously emitted by itself at
the same rate, keeping the curvature radius of de Sitter space fixed.Comment: 11 pages, REVTE
Negative modes in the four-dimensional stringy wormholes
We study the Giddings-Strominger wormholes in string theories. We found
negative modes among O(4)-symmetric fluctuations about the non-singular
wormhole background. Hence the stringy wormhole contribution to the euclidean
functional integral is purely imaginary. This means that the stringy wormhole
is a bounce (not an instanton) and describes the nucleation and growth of
wormholes in the Minkowski spacetime.Comment: 12 pages 2 figures, RevTe
Scattering from an AdS_3 bubble and an exact AdS_3
We investigate the close relationship between the potential and absorption
cross section for test fields in an AdS bubble(a 5D black hole) and an
exact AdS. There are two solutions in type IIB string theory: an AdS
bubble corresponds to the dilatonic solution, while an exact AdS is the
non-dilatonic solution. In order to obtain the cross section for an AdS
bubble, we introduce the \{out\}-state scattering picture with the AdS-AFS
matching procedure. For an exact AdS, one considers the \{in\}-state
scattering picture with the AdS-AdS matching. Here the non-normalizable
modes are crucially taken into account for the matching procedure. It turns out
that the cross sections for the test fields in an AdS bubble take the same
forms as those in an exact AdS. This suggests that in the dilute gas and
the low energy limits, the S-matrix for an AdS bubble can be derived from
an exact AdS space.Comment: revised version to appear in Physical Review D, 26 pages with
embedded 5 EPS figures in RevTex forma
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