1,720,972 research outputs found
Phase transitions between Reissner-Nordstrom and dilatonic black holes in 4D AdS spacetime
No full textWe study Einstein-Maxwell-dilaton gravity models in four-dimensional antide
Sitter (AdS) spacetime which admit the Reissner-Nordstrom (RN) black hole solution.
We show that below a critical temperature the AdS-RN solution becomes unstable against
scalar perturbations and the gravitational system undergoes a phase transition. We show
using numerical calculations that the new phase is a charged dilatonic black hole. Using
the AdS/CFT correspondence we discuss the phase transition in the dual field theory both
for non-vanishing temperatures and in the extremal limit. The extremal solution has a
Lifshitz scaling symmetry. We discuss the optical conductivity in the new dual phase
and find interesting behavior at low frequencies where it shows a “Drude peak”. The
resistivity varies with temperature in a non-monotonic way and displays a minimum at low
temperatures which is reminiscent of the celebrated Kondo effect
Gravitational waves from WZW models
No full textContribution to the proceedings of the RTN-workshop ``The quantum structure of space-time and the geometrical nature of the fundamental interactions'', Copenhagen, September 15-20, 2003International audienceA brief review is given of the recent solution of a non-compact CFT describing a NS-supported pp-wave background. We will first explain how to compute the three and four-point correlators using current algebra techniques, thereby showing that some generic features of the non-compact WZW models become very clear in this simple context. We will then present the Penrose limit as a contraction of an U(1)xSU(2)_k WZW model, an approach that could prove useful in order to understand holography for pp-wave space-times. We will finally comment on the string amplitudes and on the existence of two flat space limits
The abelian cosets of the Heisenberg group
No full textIn this paper we study the abelian cosets of the H-4 WZW model. They coincide or are related to several interesting three-dimensional backgrounds such as the Melvin model, the conical point-particle space-times and the null orbifold. We perform a detailed CFT analysis of all the models and compute the coset characters as well as some typical three-point couplings of coset primaries
Boundary States of c=1 and 3/2 Rational Conformal Field Theories
No full textLatex, 46 pages, 1 figureInternational audienceWe study the boundary states for the rational points in the moduli spaces of c=1 conformal and c=3/2 superconformal field theories, including the isolated Ginsparg points. We use the orbifold and simple-current techniques to relate the boundary states of different theories and to obtain symmetry-breaking, non-Cardy boundary states. We show some interesting examples of fractional and twisted branes on orbifold spaces
The diagonal cosets of the Heisenberg group
No full textIn this paper we study the diagonal cosets of the non-compact H-4 WZW model. Generalising earlier work by Antoniadis and Obers, we provide an exact world-sheet description for several families of non-maximally symmetric gravitational plane waves with background NS fluxes. We show that the sigma-models that correspond to an asymmetric action of the gauge group smoothly interpolate between singular and non-singular plane waves. We also analyse the representations of the coset chiral algebra and derive the spectrum of all the models
A microscopic description of absorption in high-energy string-brane collisions
Full text linkWe study the collision of a highly energetic light closed string off a stack of Dp-branes at (sub)string-scale impact parameters and in a regime justifying a perturbative treatment. Unlike at larger impact parameters - where elastic scattering and/or tidal excitations dominate - here absorption of the closed string by the brane system, with the associated excitation of open strings living on it, becomes important. As a first step, we study this phenomenon at the disk level, in which the energetic closed string turns into a single heavy open string at rest whose particularly simple properties are described.We study the collision of a highly energetic light closed string off a stack of Dp-branes at (sub)string-scale impact parameters and in a regime justifying a perturbative treatment. Unlike at larger impact parameters — where elastic scattering and/or tidal excitations dominate — here absorption of the closed string by the brane system, with the associated excitation of open strings living on it, becomes important. As a first step, we study this phenomenon at the disk level, in which the energetic closed string turns into a single heavy open string at rest whose particularly simple properties are described.We study the collision of a highly energetic light closed string off a stack of Dp-branes at (sub)string-scale impact parameters and in a regime justifying a perturbative treatment. Unlike at larger impact parameters - where elastic scattering and/or tidal excitations dominate - here absorption of the closed string by the brane system, with the associated excitation of open strings living on it, becomes important. As a first step, we study this phenomenon at the disk level, in which the energetic closed string turns into a single heavy open string at rest whose particularly simple properties are described
- …
