52 research outputs found
Supergravity Black Holes and Billiards and Liouville integrable structure of dual Borel algebras
In this paper we show that the supergravity equations describing both cosmic
billiards and a large class of black-holes are, generically, both Liouville
integrable as a consequence of the same universal mechanism. This latter is
provided by the Liouville integrable Poissonian structure existing on the dual
Borel algebra B_N of the simple Lie algebra A_{N-1}. As a by product we derive
the explicit integration algorithm associated with all symmetric spaces U/H^{*}
relevant to the description of time-like and space-like p-branes. The most
important consequence of our approach is the explicit construction of a
complete set of conserved involutive hamiltonians h_{\alpha} that are
responsible for integrability and provide a new tool to classify flows and
orbits. We believe that these will prove a very important new tool in the
analysis of supergravity black holes and billiards.Comment: 48 pages, 7 figures, LaTex; V1: misprints corrected, two references
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Inverse Scattering Construction of a Dipole Black Ring
Using the inverse scattering method in six dimensions we construct the dipole
black ring of five dimensional Einstein-Maxwell-dilaton theory with dilaton
coupling a = 2(2/3)^(1/2).The 5d theory can be thought of as the NS sector of
low energy string theory in Einstein frame. It can also be obtained by
dimensionally reducing six-dimensional vacuum gravity on a circle. Our new
approach uses GL(4, R) integrability structure of the theory inherited from
six-dimensional vacuum gravity. Our approach is also general enough to
potentially generate dipole black objects carrying multiple rotations as well
as more exotic multi-horizon configurations
Lifshitz spacetimes from AdS null and cosmological solutions
We describe solutions of 10-dimensional supergravity comprising null
deformations of with a scalar field, which have
Lifshitz symmetries. The bulk Lifshitz geometry in 3+1-dimensions arises by
dimensional reduction of these solutions. The dual field theory in this case is
a deformation of the N=4 super Yang-Mills theory. We discuss the holographic
2-point function of operators dual to bulk scalars. We further describe
time-dependent (cosmological) solutions which have anisotropic Lifshitz scaling
symmetries. We also discuss deformations of in 11-dimensional
supergravity, which are somewhat similar to the solutions above. In some cases
here, we expect the field theory duals to be deformations of the Chern-Simons
theories on M2-branes stacked at singularities.Comment: Latex, 29pgs, v3. references, minor clarifications (subsection on
Lifshitz geometry seen by scalar probes) added, to appear in JHE
Vortices in (2+1)d Conformal Fluids
We study isolated, stationary, axially symmetric vortex solutions in
(2+1)-dimensional viscous conformal fluids. The equations describing them can
be brought to the form of three coupled first order ODEs for the radial and
rotational velocities and the temperature. They have a rich space of solutions
characterized by the radial energy and angular momentum fluxes. We do a
detailed study of the phases in the one-parameter family of solutions with no
energy flux. This parameter is the product of the asymptotic vorticity and
temperature. When it is large, the radial fluid velocity reaches the speed of
light at a finite inner radius. When it is below a critical value, the velocity
is everywhere bounded, but at the origin there is a discontinuity. We comment
on turbulence, potential gravity duals, non-viscous limits and non-relativistic
limits.Comment: 39 pages, 10 eps figures, v2: Minor changes, refs, preprint numbe
An electrically charged doubly spinning dipole black ring
We present a new asymptotically flat, doubly spinning black ring of D = 5
Einstein-Maxwell-dilaton theory with Kaluza-Klein dilaton coupling. Besides the
mass and two angular momenta, the solution displays both electric charge and
(magnetic) dipole charge. The class of solutions that are free from conical
singularities is described by four parameters. We first derive the solution in
six dimensions employing the inverse scattering method, thereby generalising
the inverse-scattering construction by two of the current authors of Emparan's
singly spinning dipole black ring. The novel black ring itself arises upon
circle Kaluza-Klein reduction. We also compute the main physical properties and
asymptotic charges of our new class of solutions. Finally, we present a
five-parameter generalisation of our solution.Comment: v2: Improved presentation with new additions including plots of some
physical charges and a new appendix with the most general five-parameter
solution. Version to be published in JHE
Image informatics strategies for deciphering neuronal network connectivity
Brain function relies on an intricate network of highly dynamic neuronal connections that rewires dramatically under the impulse of various external cues and pathological conditions. Among the neuronal structures that show morphologi- cal plasticity are neurites, synapses, dendritic spines and even nuclei. This structural remodelling is directly connected with functional changes such as intercellular com- munication and the associated calcium-bursting behaviour. In vitro cultured neu- ronal networks are valuable models for studying these morpho-functional changes. Owing to the automation and standardisation of both image acquisition and image analysis, it has become possible to extract statistically relevant readout from such networks. Here, we focus on the current state-of-the-art in image informatics that enables quantitative microscopic interrogation of neuronal networks. We describe the major correlates of neuronal connectivity and present workflows for analysing them. Finally, we provide an outlook on the challenges that remain to be addressed, and discuss how imaging algorithms can be extended beyond in vitro imaging studies
Stochastic Gravity: Theory and Applications
Whereas semiclassical gravity is based on the semiclassical Einstein equation
with sources given by the expectation value of the stress-energy tensor of
quantum fields, stochastic semiclassical gravity is based on the
Einstein-Langevin equation, which has in addition sources due to the noise
kernel.In the first part, we describe the fundamentals of this new theory via
two approaches: the axiomatic and the functional. In the second part, we
describe three applications of stochastic gravity theory. First, we consider
metric perturbations in a Minkowski spacetime: we compute the two-point
correlation functions for the linearized Einstein tensor and for the metric
perturbations. Second, we discuss structure formation from the stochastic
gravity viewpoint. Third, we discuss the backreaction of Hawking radiation in
the gravitational background of a quasi-static black hole.Comment: 75 pages, no figures, submitted to Living Reviews in Relativit
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