11,343 research outputs found
Black hole dynamics from instanton strings
A D-5-brane bound state with a self-dual field strength on a 4-torus is
considered. In a particular case this model reproduces the D5-D1 brane bound
state usually used in the string theory description of 5-dimensional black
holes. In the limit where the brane dynamics decouples from the bulk the Higgs
and Coulomb branches of the theory on the brane decouple. Contrasting with the
usual instanton moduli space approximation to the problem the Higgs branch
describes fundamental excitations of the gauge field on the brane. Upon
reduction to 2-dimensions it is associated with the so-called instanton
strings. Using the Born-Infeld action for the D-5-brane we determine the
coupling of these strings to a minimally coupled scalar in the black hole
background. The supergravity calculation of the cross section is found to agree
with the D-brane absorption probability rate calculation. We consider the near
horizon geometry of our black hole and elaborate on the corresponding duality
with the Higgs branch of the gauge theory in the large N limit. A heuristic
argument for the scaling of the effective string tension is given.Comment: 37 pages, latex. Typos corrected, SUSY field configuration argued to
be valid even when DBI corrections are important and two references adde
Black Composite M-branes
We generalise all the known supersymmetric composite M-branes to the
corresponding black configurations. Thermodynamical formulae is written by
using the simple rules to construct these black branes.Comment: 14 pages, latex. Revised version to appear in Nuclear Physics
Conformal correlators of mixed-symmetry tensors
We generalize the embedding formalism for conformal field theories to the
case of general operators with mixed symmetry. The index-free notation encoding
symmetric tensors as polynomials in an auxiliary polarization vector is
extended to mixed-symmetry tensors by introducing a new commuting or
anticommuting polarization vector for each row or column in the Young diagram
that describes the index symmetries of the tensor. We determine the tensor
structures that are allowed in n-point conformal correlation functions and give
an algorithm for counting them in terms of tensor product coefficients. A
simple derivation of the unitarity bound for arbitrary mixed-symmetry tensors
is obtained by considering the conservation condition in embedding space. We
show, with an example, how the new formalism can be used to compute conformal
blocks of arbitrary external fields for the exchange of any conformal primary
and its descendants. The matching between the number of tensor structures in
conformal field theory correlators of operators in d dimensions and massive
scattering amplitudes in d+1 dimensions is also seen to carry over to
mixed-symmetry tensors.Comment: 46 pages, many figures, v2: Reformulated the counting of tensor
structures, new section on conserved operators, v3: fixed typo
Landau degeneracy and black hole entropy
We consider the supergravity solution describing a configuration of
intersecting D-4-branes with non-vanishing worldvolume gauge fields. The
entropy of such a black hole is calculated in terms of the D-branes quantised
charges. The non-extreme solution is also considered and the corresponding
thermodynamical quantities are calculated in terms of a D-brane/anti-D-brane
system. To perform the quantum mechanical D-brane analysis we study
open-strings with their ends on branes with a magnetic condensate. Applying the
results to our D-brane system we managed to have a perfect agreement between
the D-brane entropy counting and the corresponding semi-classical result. The
Landau degeneracy of the open string states describing the excitations of the
D-brane system enters in a crucial way. We also derive the near-extreme results
which agree with the semi-classical calculations.Comment: 30 pages, 1 figure, latex. Minor corrections, version to appear in
Nuclear Physics
- …