265 research outputs found
N=2 Super-EYM coloured black holes from defective Lax matrices
We construct analytical supersymmetric coloured black hole solutions, i.e.
non-Abelian black hole solutions that have no asymptotic non-Abelian charge but
do have non-Abelian charges on the horizon that contribute to the
Bekenstein-Hawking entropy, to two SU(3)-gauged N=2 d= supergravities. The
analytical construction is made possible due to the fact that the main
ingredient is the Bogomol'nyi equation, which under the assumption of spherical
symmetry admits a Lax pair formulation. The Lax matrix needed for the coloured
black holes must be defective which, even though it is the non-generic and less
studied case, is a minor hindrance.Comment: 20 pages, 1 figure; to be published versio
Massless Black Holes as Black Diholes and Quadruholes
Massless black holes can be understood as bound states of a (positive mass)
extreme a=\sqrt{3} black hole and a singular object with opposite (i.e.
negative) mass with vanishing ADM (total) mass but non-vanishing gravitational
field. Supersymmetric balance of forces is crucial for the existence of this
kind of bound states and explains why the system does not move at the speed of
light. We also explain how supersymmetry allows for negative mass as long as it
is never isolated but in bound states of total non-negative mass.Comment: Version to be published in Physical Review Letters. Latex2e fil
Duality Versus Supersymmetry and Compactification
We study the interplay between T-duality, compactification and supersymmetry.
We prove that when the original configuration has unbroken space-time
supersymmetries, the dual configuration also does if a special condition is
met: the Killing spinors of the original configuration have to be independent
on the coordinate which corresponds to the isometry direction of the bosonic
fields used for duality. Examples of ``losers" (T-duals are not supersymmetric)
and ``winners" (T-duals are supersymmetric) are given.Comment: LaTeX file, 19 pages, U. of Groningen Report UG-8/94, Stanford U.
Report SU-ITP-94-19, QMW College Report QMW-PH-94-1
The Internal Spin Angular Momentum of an Asymptotically Flat Spacetime
In this paper we investigate the manner in which the internal spin angular
momentum of a spinor field is encoded in the gravitational field at asymptotic
infinity. The inclusion of internal spin requires us to re-analyze our notion
of asymptotic flatness. In particular, the Poincar\'{e} symmetry at asymptotic
infinity must replaced by a spin-enlarged Poincar\'{e} symmetry. Likewise, the
generators of the asymptotic symmetry group must be supplemented to account for
the internal spin. In the Hamiltonian framework of first order Einstein-Cartan
gravity, the extra generator comes from the boundary term of the Gauss
constraint in the asymptotically flat context. With the additional term, we
establish the relations among the Noether charges of a Dirac field, the Komar
integral, and the asymptotic ADM-like geometric integral. We show that by
imposing mild restraints on the generating functionals of gauge transformations
at asymptotic infinity, the phase space is rendered explicitly finite. We
construct the energy-momentum and the new total (spin+orbital) angular momentum
boundary integrals that satisfy the appropriate algebra to be the generators of
the spin-enlarged Poincar\'{e} symmetry. This demonstrates that the internal
spin is encoded in the tetrad at asymptotic infinity. In addition, we find that
a new conserved and (spin-enlarged) Poincar\'{e} invariant charge emerges that
is associated with the global structure of a gauge transformation.Comment: V2: No major changes, journal reference adde
The FGK formalism for black p-branes in d dimensions
We present a generalization to an arbitrary number of spacetime (d) and
worldvolume (p+1) dimensions of the formalism proposed by Ferrara, Gibbons and
Kallosh to study black holes (p=0) in d=4 dimensions. We include the special
cases in which there can be dyonic and self- or anti-self-dual black branes.
Most of the results valid for 4-dimensional black holes (relations between
temperature, entropy and non-extremality parameter, and between entropy and
black-hole potential on the horizon) are straightforwardly generalized.
We apply the formalism to the case of black strings in N=2,d=5 supergravity
coupled to vector multiplets, in which the black-string potential can be
expressed in terms of the dual central charge and work out an explicit example
with one vector multiplet, determining supersymmetric and non-supersymmetric
attractors and constructing the non-extremal black-string solutions that
interpolate between them.Comment: 28 pages no figures; v2: some references adde
An Efficient Platform for the Automatic Extraction of Patterns in Native Code
Different software tools, such as decompilers, code quality analyzers, recognizers of packed executable files, authorship analyzers, and malware detectors, search for patterns in binary code. The use of machine learning algorithms, trained with programs taken from the huge number of applications in the existing open source code repositories, allows finding patterns not detected with the manual approach. To this end, we have created a versatile platform for the automatic extraction of patterns from native code, capable of processing big binary files. Its implementation has been parallelized, providing important runtime performance benefits for multicore architectures. Compared to the single-processor execution, the average performance improvement obtained with the best configuration is 3.5 factors over the maximum theoretical gain of 4 factors
Torsion cosmological dynamics
In this paper, the dynamical attractor and heteroclinic orbit have been
employed to make the late-time behaviors of the model insensitive to the
initial condition and thus alleviate the fine-tuning problem in the torsion
cosmology. The late-time de Sitter attractor indicates that torsion cosmology
is an elegant scheme and the scalar torsion mode is an interesting geometric
quantity for physics. The numerical solutions obtained by Nester et al. are not
periodic solutions, but are quasi-periodic solutions near the focus for the
coupled nonlinear equations.Comment: 4 pages, 3 figure
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