6,978 research outputs found
Near Horizon Extremal Geometry Perturbations: Dynamical Field Perturbations vs. Parametric Variations
In arXiv:1310.3727 we formulated and derived the three universal laws
governing Near Horizon Extremal Geometries (NHEG). In this work we focus on the
Entropy Perturbation Law (EPL) which, similarly to the first law of black hole
thermodynamics, relates perturbations of the charges labeling perturbations
around a given NHEG to the corresponding entropy perturbation. We show that
field perturbations governed by the linearized equations of motion and symmetry
conditions which we carefully specify, satisfy the EPL. We also show that these
perturbations are limited to those coming from difference of two NHEG solutions
(i.e. variations on the NHEG solution parameter space). Our analysis and
discussions shed light on the "no-dynamics" statements of arXiv:0906.2380 and
arXiv:0906.2376.Comment: 38 page
Extremal Rotating Black Holes in the Near-Horizon Limit: Phase Space and Symmetry Algebra
We construct the NHEG phase space, the classical phase space of Near-Horizon
Extremal Geometries with fixed angular momenta and entropy, and with the
largest symmetry algebra. We focus on vacuum solutions to dimensional
Einstein gravity. Each element in the phase space is a geometry with
isometries which has vanishing and constant charges. We construct an on-shell vanishing symplectic
structure, which leads to an infinite set of symplectic symmetries. In four
spacetime dimensions, the phase space is unique and the symmetry algebra
consists of the familiar Virasoro algebra, while in dimensions the
symmetry algebra, the NHEG algebra, contains infinitely many Virasoro
subalgebras. The nontrivial central term of the algebra is proportional to the
black hole entropy. This phase space and in particular its symmetries might
serve as a basis for a semiclassical description of extremal rotating black
hole microstates.Comment: Published in PLB, 5 page
Wiggling Throat of Extremal Black Holes
We construct the classical phase space of geometries in the near-horizon
region of vacuum extremal black holes as announced in [arXiv:1503.07861].
Motivated by the uniqueness theorems for such solutions and for perturbations
around them, we build a family of metrics depending upon a single periodic
function defined on the torus spanned by the isometry directions. We
show that this set of metrics is equipped with a consistent symplectic
structure and hence defines a phase space. The phase space forms a
representation of an infinite dimensional algebra of so-called symplectic
symmetries. The symmetry algebra is an extension of the Virasoro algebra whose
central extension is the black hole entropy. We motivate the choice of
diffeomorphisms leading to the phase space and explicitly derive the symplectic
structure, the algebra of symplectic symmetries and the corresponding conserved
charges. We also discuss a formulation of these charges with a Liouville type
stress-tensor on the torus defined by the isometries and outline
possible future directions.Comment: 56 pages, 3 figure
Spreading depression triggers ictal activity in disinhibited hippocampal slices
Die enge Verwandtschaft zwischen der Spreading depression (SD) und experimenteller epileptischer Aktivität hat zu zahlreichen Untersuchungen zum Wechselspiel dieser zwei Phänomene gefßhrt. Trotz dieser Untersuchungen in verschiedenen Tiermodellen, ist der genaue Zusammenhang zwischen SD und epileptiformer Feldpotentiale unklar. Daher wurde in der vorliegenden Arbeit die Interaktion von SD und experimenteller epileptischer Aktivität in hippocampalen Rattenhirnschnitten untersucht
On the Solution of the Number-Projected Hartree-Fock-Bogoliubov Equations
The numerical solution of the recently formulated number-projected
Hartree-Fock-Bogoliubov equations is studied in an exactly soluble
cranked-deformed shell model Hamiltonian. It is found that the solution of
these number-projected equations involve similar numerical effort as that of
bare HFB. We consider that this is a significant progress in the mean-field
studies of the quantum many-body systems. The results of the projected
calculations are shown to be in almost complete agreement with the exact
solutions of the model Hamiltonian. The phase transition obtained in the HFB
theory as a function of the rotational frequency is shown to be smeared out
with the projection.Comment: RevTeX, 11 pages, 3 figures. To be published in a special edition of
Physics of Atomic Nuclei (former Sov. J. Nucl. Phys.) dedicated to the 90th
birthday of A.B. Migda
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