2,716 research outputs found
BPS black holes, the Hesse potential, and the topological string
The Hesse potential is constructed for a class of four-dimensional N=2
supersymmetric effective actions with S- and T-duality by performing the
relevant Legendre transform by iteration. It is a function of fields that
transform under duality according to an arithmetic subgroup of the classical
dualities reflecting the monodromies of the underlying string compactification.
These transformations are not subject to corrections, unlike the
transformations of the fields that appear in the effective action which are
affected by the presence of higher-derivative couplings. The class of actions
that are considered includes those of the FHSV and the STU model. We also
consider heterotic N=4 supersymmetric compactifications. The Hesse potential,
which is equal to the free energy function for BPS black holes, is manifestly
duality invariant. Generically it can be expanded in terms of powers of the
modulus that represents the inverse topological string coupling constant,
, and its complex conjugate. The terms depending holomorphically on
are expected to correspond to the topological string partition function and
this expectation is explicitly verified in two cases. Terms proportional to
mixed powers of and are in principle present.Comment: 28 pages, LaTeX, added comment
Numerical relativity for D dimensional axially symmetric space-times: formalism and code tests
The numerical evolution of Einstein's field equations in a generic background
has the potential to answer a variety of important questions in physics: from
applications to the gauge-gravity duality, to modelling black hole production
in TeV gravity scenarios, analysis of the stability of exact solutions and
tests of Cosmic Censorship. In order to investigate these questions, we extend
numerical relativity to more general space-times than those investigated
hitherto, by developing a framework to study the numerical evolution of D
dimensional vacuum space-times with an SO(D-2) isometry group for D\ge 5, or
SO(D-3) for D\ge 6.
Performing a dimensional reduction on a (D-4)-sphere, the D dimensional
vacuum Einstein equations are rewritten as a 3+1 dimensional system with source
terms, and presented in the Baumgarte, Shapiro, Shibata and Nakamura (BSSN)
formulation. This allows the use of existing 3+1 dimensional numerical codes
with small adaptations. Brill-Lindquist initial data are constructed in D
dimensions and a procedure to match them to our 3+1 dimensional evolution
equations is given. We have implemented our framework by adapting the LEAN code
and perform a variety of simulations of non-spinning black hole space-times.
Specifically, we present a modified moving puncture gauge which facilitates
long term stable simulations in D=5. We further demonstrate the internal
consistency of the code by studying convergence and comparing numerical versus
analytic results in the case of geodesic slicing for D=5,6.Comment: 31 pages, 6 figures; v2 Minor changes and added two references.
Matches the published version in PRD
Extensive local adaptation within the chemosensory system following Drosophila melanogaster’s global expansion
No entropy enigmas for N=4 dyons
We explain why multi-centered black hole configurations where at least one of
the centers is a large black hole do not contribute to the indexed degeneracies
in theories with N=4 supersymmetry. This is a consequence of the fact that such
configurations, although supersymmetric, belong to long supermultiplets. As a
result, there is no entropy enigma in N=4 theories, unlike in N=2 theories.Comment: 14 page
A Twist in the Dyon Partition Function
In four dimensional string theories with N=4 and N=8 supersymmetries one can
often define twisted index in a subspace of the moduli space which captures
additional information on the partition function than the ones contained in the
usual helicity trace index. We compute several such indices in type IIB string
theory on K3 x T^2 and T^6, and find that they share many properties with the
usual helicity trace index that captures the spectrum of quarter BPS states in
N=4 supersymmetric string theories. In particular the partition function is a
modular form of a subgroup of Sp(2,Z) and the jumps across the walls of
marginal stability are controlled by the residues at the poles of the partition
function. However for large charges the logarithm of this index grows as 1/n
times the entropy of a black hole carrying the same charges where n is the
order of the symmetry generator that is used to define the twisted index. We
provide a macroscopic explanation of this phenomenon using quantum entropy
function formalism. The leading saddle point corresponding to the attractor
geometry fails to contribute to the twisted index, but a Z_n orbifold of the
attractor geometry produces the desired contribution.Comment: LaTeX file, 35 pages; v2: references adde
Phase diagram for non-axisymmetric plasma balls
Plasma balls and rings emerge as fluid holographic duals of black holes and
black rings in the hydrodynamic/gravity correspondence for the Scherk-Schwarz
AdS system. Recently, plasma balls spinning above a critical rotation were
found to be unstable against m-lobed perturbations. In the phase diagram of
stationary solutions the threshold of the instability signals a bifurcation to
a new phase of non-axisymmetric configurations. We find explicitly this family
of solutions and represent them in the phase diagram. We discuss the
implications of our results for the gravitational system. Rotating
non-axisymmetric black holes necessarily radiate gravitational waves. We thus
emphasize that it would be important, albeit possibly out of present reach, to
have a better understanding of the hydrodynamic description of gravitational
waves and of the gravitational interaction between two bodies. We also argue
that it might well be that a non-axisymmetric m-lobed instability is also
present in Myers-Perry black holes for rotations below the recently found
ultraspinning instability.Comment: 1+22 pages, 3 figures. v2: minor corrections and improvements,
matches published versio
Discrete Information from CHL Black Holes
AdS_2/CFT_1 correspondence predicts that the logarithm of a Z_N twisted index
over states carrying a fixed set of charges grows as 1/N times the entropy of
the black hole carrying the same set of charges. In this paper we verify this
explicitly by calculating the microscopic Z_N twisted index for a class of
states in the CHL models. This demonstrates that black holes carry more
information about the microstates than just the total degeneracy.Comment: LaTeX file, 24 pages; v2: references adde
Counting all dyons in N =4 string theory
For dyons in heterotic string theory compactified on a six-torus, with
electric charge vector Q and magnetic charge vector P, the positive integer I =
g.c.d.(Q \wedge P) is an invariant of the U-duality group. We propose the
microscopic theory for computing the spectrum of all dyons for all values of I,
generalizing earlier results that exist only for the simplest case of I=1. Our
derivation uses a combination of arguments from duality, 4d-5d lift, and a
careful analysis of fermionic zero modes. The resulting degeneracy agrees with
the black hole degeneracy for large charges and with the degeneracy of
field-theory dyons for small charges. It naturally satisfies several physical
requirements including integrality and duality invariance. As a byproduct, we
also derive the microscopic (0,4) superconformal field theory relevant for
computing the spectrum of five-dimensional Strominger-Vafa black holes in ALE
backgrounds and count the resulting degeneracies
Logarithmic Corrections to Extremal Black Hole Entropy from Quantum Entropy Function
We evaluate the one loop determinant of matter multiplet fields of N=4
supergravity in the near horizon geometry of quarter BPS black holes, and use
it to calculate logarithmic corrections to the entropy of these black holes
using the quantum entropy function formalism. We show that even though
individual fields give non-vanishing logarithmic contribution to the entropy,
the net contribution from all the fields in the matter multiplet vanishes. Thus
logarithmic corrections to the entropy of quarter BPS black holes, if present,
must be independent of the number of matter multiplet fields in the theory.
This is consistent with the microscopic results. During our analysis we also
determine the complete spectrum of small fluctuations of matter multiplet
fields in the near horizon geometry.Comment: LaTeX file, 52 pages; v2: minor corrections, references adde
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