We study various aspects of orientifold projections of Type IIB closed string

We provide a holographic description of two-dimensional dilaton gravity with Anti-de Sitter boundary conditions. We find that the asymptotic symmetry algebra consists of a single copy of the Virasoro algebra with non-vanishing central charge and point out difficulties with the standard canonical treatment. We generalize our results to higher spin theories and thus provide the first examples of two-dimensional higher spin gravity with holographic description. For spin-3 gravity we find that the asymptotic symmetry algebra is a single copy of the W3-algebra.

Resorting to the notion of a stress-tensor induced on the boundary of a spacetime, we compute the conserved charges associated to exact solutions of New Massive Gravity that obey weakened versions of AdS3 asymptotic boundary conditions. The computation requires the introduction of additional counterterms, which play the rôle of regularizing the semiclassical stress-tensor in the boundary theory. We show that, if treated appropriately, different ways of prescribing asymptotically AdS3 boundary conditions yield finite conserved charges for the solutions. The consistency of the construction manifests itself in that the charges of hairy asymptotically AdS3 black holes computed by this holography-inspired method exactly match the values required for the Cardy formula to reproduce the black hole entropy. We also consider new solutions to the equations of motion of New Massive Gravity, which happen to fulfill Brown-Henneaux boundary conditions despite not being Einstein manifolds. These solutions are shown to yield vanishing boundary stress-tensor. The results obtained in this paper can be regarded as consistency checks for the prescription proposed in [1].Topologically Massive Gravity [14] with negative cosmological constant seems to lose its local degree of freedom and, at the same time, the central charge of the left-moving sector of the asymptotic symmetry algebra vanishes. This observation led the authors of [13] to conjecture that, for a specific choice of the coupling constant, Topologically Massive Gravity is dual to a holomorphic (chiral) conformal field theory. This proposal is usually referred to as the "Chiral Gravity Conjecture", and it was extensively discussed in the recent literature [15]. Subsequently we learned that the realization of the ideas of [13] sensibly depends on the way the asymptotic boundary conditions are prescribed. Actually, this is not surprising; after all, it is well established that the asymptotic AdS boundary conditions may differ from one theory to another [16], and, besides, a given theory may admit more than one set of consistent boundary conditions. Therefore, the discussion on the validity of the proposal in [13] resulted in a discussion on how to define what "asymptotically AdS 3 space" actually means in this context. This issue was eventually clarified in [17], where it was pointed out that two different theories, both defined by the same Lagrangian but imposing two alternative sets of boundary conditions for each one, seem to exist. While one of these theories turns out to be dual to a chiral CFT, the other one, defined by imposing weakened boundary conditions, is believed to be dual to a Logarithmic CFT [17][18][19]. This is, indeed, far from being a minor difference, as a Logarithmic CFT is necessarily non-unitary, giving raise to the question on whether the dual CFT picture really makes sense if weakened asymptotic conditions are imposed. Therefore, the lesson we learn from the recent discussions on three-dimensional chiral gravity was actually instructive: It provides us...

Abstract:We revisit the description of the space of asymptotically AdS 3 solutions of pure gravity in three dimensions with a negative cosmological constant as a collection of coadjoint orbits of the Virasoro group. Each orbit corresponds to a set of metrics related by diffeomorphisms which do not approach the identity fast enough at the boundary. Orbits contain more than a single element and this fact manifests the global degrees of freedom of AdS 3 gravity, being each element of an orbit what we call boundary graviton. We show how this setup allows to learn features about the classical phase space that otherwise would be quite difficult. Most important are the proof of energy bounds and the characterization of boundary gravitons unrelated to BTZs and AdS 3 . In addition, it makes manifest the underlying mathematical structure of the space of solutions close to infinity. Notably, because of the existence of a symplectic form in each orbit, being this related with the usual Dirac bracket of the asymptotic charges, this approach is a natural starting point for the quantization of different sectors of AdS3 gravity. We finally discuss previous attempts to quantize coadjoint orbits of the Virasoro group and how this is relevant for the formulation of AdS 3 quantum gravity.

We consider scalar field perturbations about asymptotically Lifshitz black holes with dynamical exponent z in D dimensions. We show that, for suitable boundary conditions, these Lifshitz black holes are stable under scalar field perturbations. For z=2, we explicitly compute the quasinormal mode frecuencies, which result to be purely imaginary, and then obtain the damping-off of the scalar field perturbation in these backgrounds. The general analysis includes, in particular, the z=3 black hole solution of three-dimensional massive gravity.Comment: 13 pages, no figures. v2: 14 pages, references added. To appear on PR