767 research outputs found
A Closed Contour of Integration in Regge Calculus
The analytic structure of the Regge action on a cone in dimensions over a
boundary of arbitrary topology is determined in simplicial minisuperspace. The
minisuperspace is defined by the assignment of a single internal edge length to
all 1-simplices emanating from the cone vertex, and a single boundary edge
length to all 1-simplices lying on the boundary. The Regge action is analyzed
in the space of complex edge lengths, and it is shown that there are three
finite branch points in this complex plane. A closed contour of integration
encircling the branch points is shown to yield a convergent real wave function.
This closed contour can be deformed to a steepest descent contour for all sizes
of the bounding universe. In general, the contour yields an oscillating wave
function for universes of size greater than a critical value which depends on
the topology of the bounding universe. For values less than the critical value
the wave function exhibits exponential behaviour. It is shown that the critical
value is positive for spherical topology in arbitrary dimensions. In three
dimensions we compute the critical value for a boundary universe of arbitrary
genus, while in four and five dimensions we study examples of product manifolds
and connected sums.Comment: 16 pages, Latex, To appear in Gen. Rel. Gra
Greybody factor for the BTZ black hole and a 5D black hole
We study the 5D black holes in the type IIB superstring theory compactified
on . Far from horizon, we have flat space-time. Near horizon,
we have . We calculate the
greybody factor of a minimally coupled scalar by replacing the original
geometry() by . In the
low-energy scattering, it turns out that the result agrees with the greybody
factor of the 5D black hole (or D1 + D5 branes)in the dilute gas approximation.
This confirms that the -theory() contains the
essential information about the bulk 5D black holes.Comment: some discussions are added, 15 Pages, No figure, RevTe
Conformal Quantum Mechanics in Two Black Hole Moduli Space
We discuss quantum mechanics in the moduli space consisting of two maximally
charged dilaton black holes. The quantum mechanics of the two black hole system
is similar to the one of DFF model, and this system has the conformal
symmetry. Also, we discuss the bound states in this system.Comment: 15 pages, RevTeX3.0. References added, Minor correction
A doubly covariant formula of deficit angle and its application to six-dimensional braneworld
We reformulate boundary conditions for axisymmetric codimension-2 braneworlds
in a way which is applicable to linear perturbation with various gauge
conditions. Our interest is in the thin brane limit and thus this scheme
assumes that the perturbations are also axisymmetric and that the surface
energy-momentum tensor of the brane is proportional to its induced metric. An
advantage of our scheme is that it allows much more freedom for convenient
coordinate choices than the other methods. This is because in our scheme, the
coordinate system in the bulk and that on the brane are completely
disentangled. Therefore, the latter does not need to be a subset of the former
and the brane does not need to stay at a fixed bulk coordinate position. The
boundary condition is manifestly doubly covariant: it is invariant under gauge
transformations in the bulk and at the same time covariant under those on the
brane. We take advantage of the double covariance when we analyze the linear
perturbation of a particular model of six-dimensional braneworld with warped
flux compactification.Comment: 25 pages, REVTeX4; published in CQ
Relaxation in Conformal Field Theory, Hawking-Page Transition, and Quasinormal/Normal Modes
We study the process of relaxation back to thermal equilibrium in
-dimensional conformal field theory at finite temperature. When the size
of the system is much larger than the inverse temperature, perturbations decay
exponentially with time. On the other hand, when the inverse temperature is
large, the relaxation is oscillatory with characteristic period set by the size
of the system. We then analyse the intermediate regime in two specific models,
namely free fermions, and a strongly coupled large conformal field
theory which is dual to string theory on -dimensional anti-de Sitter
spacetime. In the latter case, there is a sharp transition between the two
regimes in the limit, which is a manifestation of the
gravitational Hawking-Page phase transition. In particular, we establish a
direct connection between quasinormal and normal modes of the gravity system,
and the decaying and oscillating behaviour of the conformal field theory.Comment: 10 pages, latex, no figure
Discrete structures in gravity
Discrete approaches to gravity, both classical and quantum, are reviewed
briefly, with emphasis on the method using piecewise-linear spaces. Models of
3-dimensional quantum gravity involving 6j-symbols are then described, and
progress in generalising these models to four dimensions is discussed, as is
the relationship of these models in both three and four dimensions to
topological theories. Finally, the repercussions of the generalisations are
explored for the original formulation of discrete gravity using edge-length
variables.Comment: 30 pages, 4 figure
Differential Regularization of Topologically Massive Yang-Mills Theory and Chern-Simons Theory
We apply differential renormalization method to the study of
three-dimensional topologically massive Yang-Mills and Chern-Simons theories.
The method is especially suitable for such theories as it avoids the need for
dimensional continuation of three-dimensional antisymmetric tensor and the
Feynman rules for three-dimensional theories in coordinate space are relatively
simple. The calculus involved is still lengthy but not as difficult as other
existing methods of calculation. We compute one-loop propagators and vertices
and derive the one-loop local effective action for topologically massive
Yang-Mills theory. We then consider Chern-Simons field theory as the large mass
limit of topologically massive Yang-Mills theory and show that this leads to
the famous shift in the parameter . Some useful formulas for the calculus of
differential renormalization of three-dimensional field theories are given in
an Appendix.Comment: 25 pages, 4 figures. Several typewritten errors and inappropriate
arguments are corrected, especially the correct adresses of authors are give
N=2 Supersymmetric Model with Dirac-Kahler Fermions from Generalized Gauge Theory in Two Dimensions
We investigate the generalized gauge theory which has been proposed
previously and show that in two dimensions the instanton gauge fixing of the
generalized topological Yang-Mills action leads to a twisted N=2 supersymmetric
action. We have found that the R-symmetry of N=2 supersymmetry can be
identified with the flavour symmetry of Dirac-Kahler fermion formulation. Thus
the procedure of twist allows topological ghost fields to be interpreted as the
Dirac-Kahler matter fermions.Comment: 22 pages, LaTe
Quasinormal Modes of Extremal BTZ Black Hole
Motivated by several pieces of evidence, in order to show that extreme black
holes cannot be obtained as limits of non-extremal black holes, in this article
we calculate explicitly quasinormal modes for Ba\~{n}ados, Teitelboim and
Zanelli (BTZ) extremal black hole and we showed that the imaginary part of the
frequency is zero. We obtain exact result for the scalar an fermionic
perturbations. We also showed that the frequency is bounded from below for the
existence of the normal modes (non-dissipative modes).Comment: 6 pp. Accepted Classical and Quantum Gravity. Typos corrected and
some references was added. Final Versio
Recommended from our members
NBS monograph
From Abstract: "This treatise is a source document containing information on helium resources, production, conservation, thermodynamic properties, liquefaction and refrigeration techniques, transportation and storage of liquid and safety requirements. It also contains a discussion of uses for liquid and cold gas in cryoelectronics, superconductivity, bubble chambers, cryopumping and missile and space systems.
- …