arXiv subjects

Gaston Giribet

Publications and source records attributed to Gaston Giribet.

At least 109 records · Page 6Linked to original sources

arXiv2013

Light-like Wilson loops in ABJM and maximal transcendentality

We revisit the computation of the two-loop light-like tetragonal Wilson loop for three dimensional pure Chern-Simons and N=6 Chern-Simons-matter theory, within dimensional regularization with dimensional reduction scheme. Our examination shows that, contrary to prior belief, the result respects maximal transcendentality as is the case of the four-point scattering amplitude of the theory. Remarkably, the corrected result matches exactly the scattering amplitude both in the divergent and in the finite parts, constants included.

hep-th↗

arXiv2013

On the Universality of Inner Black Hole Mechanics and Higher Curvature Gravity

Black holes are famous for their universal behavior. New thermodynamic relations have been found recently for the product of gravitational entropies over all the horizons of a given stationary black hole. This product has been found to be independent of the mass for all such solutions of Einstein-Maxwell theory in d=4,5. We study the universality of this mass independence by introducing a number of possible higher curvature corrections to the gravitational action. We consider finite temperature black holes with both asymptotically flat and (A)dS boundary conditions. Although we find examples for which mass independence of the horizon entropy product continues to hold, we show that the universality of this property fails in general. We also derive further thermodynamic properties of inner horizons, such as the first law and Smarr relation, in the higher curvature theories under consideration, as well as a set of relations between thermodynamic potentials on the inner and outer horizons that follow from the horizon entropy product, whether or not it is mass independent.

hep-th↗

arXiv2013

The 1/2 BPS Wilson loop in ABJM theory at two loops

We compute the expectation value of the 1/2 BPS circular Wilson loop in ABJM theory at two loops in perturbation theory. The result shows perfect agreement with the prediction from localization and the proposed framing factor.

hep-th↗

arXiv2013

The large D limit of dimensionally continued gravity

In a recent paper [arXiv:1302.6382] Emparan, Suzuki, and Tanabe studied general relativity in the limit in which the number of spacetime dimensions D tends to infinity. They showed that, in such limit, the theory simplifies notably. It reduces to a theory whose fundamental objects, black holes and black branes, behave as non-interacting particles. Here, we consider a different way of extending gravity to D dimensions. We present a special limit of dimensionally continued gravity in which black holes retain their gravitational interaction at large D and still have entropy proportional to the mass. The similarities and differences with the limit considered in [arXiv:1302.6382] are discussed.

gr-qc↗

arXiv2013

On the description of surface operators in N=2* super Yang-Mills

In Ref. [arXiv:1005.4469], Alday and Tachikawa observed that the Nekrasov partition function of N=2 SU(2) superconformal gauge theories in the presence of fundamental surface operators can be associated to conformal blocks of a 2D CFT with affine sl(2) symmetry. This can be interpreted as the insertion of a fundamental surface operator changing the conformal symmetry from the Virasoro symmetry discovered in [arXiv:0906.3219] to the affine Kac-Moody symmetry. A natural question arises as to how such a 2D CFT description can be extended to the case of non-fundamental surface operators. Motivated by this question, we review the results of Refs. [arXiv:0706.1030] and [arXiv:0803.2099] and put them together to suggest a way to address the problem: It follows from this analysis that the expectation value of a non-fundamental surface operator in the SU(2) N=2* super Yang-Mills theory would be in correspondence with the expectation value of a single vertex operator in a two-dimensional CFT with reduced affine symmetry and whose central charge is parameterized by the integer number that labels the type of singularity of the surface operator.

hep-th↗

arXiv2012

New Massive Gravity on de Sitter Space and Black Holes at the Special Point

We study New Massive Gravity on de Sitter background and discuss several interrelated properties: The appearance of an enhanced symmetry point at linearized level where the theory becomes partially massless; its absence at full nonlinear level, and its relation with the existence of static black hole solutions and their hair parameter.

hep-th↗

arXiv2012

Critical gravity waves

Critical Gravity in D dimensions is discussed from the point of view of its exact solutions. The special features that certain type of solutions of higher-curvature gravity develop when one approaches the critical point of the parameter space are reviewed. In particular, a non-linear realization of the logarithmic modes of linearized Critical Gravity is seen to emerge as a peculiarity of the sector of anti-de Sitter wave solutions. Logarithmic solutions are shown to occur at a second point of the parameter space, at which the effective mass of the anti-de Sitter waves equals the Breitenlohner-Freedman bound. Other type of solutions with anisotropic scale invariance are also discussed and the special features they develop at the critical point are studied as well. This note is the written version of the talk delivered by one of the authors at the 13th Marcel Grossmann Meeting on general relativity, held in Stockholm, Sweden, in July 2012. The proceeding contribution is based on authors' previous works.

gr-qc↗

arXiv2012

Scalar field perturbations in asymptotically Lifshitz black holes

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.

hep-th↗

arXiv2012

Lifshitz black holes in Brans-Dicke theory

We present an exact asymptotically Lifshitz black hole solution in Brans-Dicke theory of gravity in arbitrary $n(\ge 3)$ dimensions in presence of a power-law potential. In this solution, the dynamical exponent $z$ is determined in terms of the Brans-Dicke parameter $ω$ and $n$. Asymptotic Lifshitz condition at infinity requires $z>1$, which corresponds to $-(n-1)/(n-2) \le ω< -n/(n-1)$. On the other hand, the no-ghost condition for the scalar field in the Einstein frame requires $0<z \le 2(n-2)/(n-3)$. We compute the Hawking temperature of the black hole solution and discuss the problems encountered and the proposals in defining its thermodynamic properties. A generalized solution charged under the Maxwell field is also presented.

gr-qc↗

arXiv2011

On the timelike Liouville three-point function

In a recent paper, D. Harlow, J. Maltz, and E. Witten showed that a particular proposal for the timelike Liouville three-point function, originally due to Al. Zamolodchikov and to I. Kostov and V. Petkova, can actually be computed by the original Liouville path integral evaluated on a new integration cycle. Here, we discuss a Coulomb gas computation of the timelike three-point function and show that an analytic extension of the Selberg type integral formulas involved reproduces the same expression, including the adequate normalization. A notable difference with the spacelike calculation is pointed out.

hep-th↗

arXiv2011

Boundary stress tensor and counterterms for weakened AdS_3 asymptotic in New Massive Gravity

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 AdS_3 asymptotic boundary conditions. The computation requires the introduction of additional counterterms, which play the role of regularizing the semiclassical stress tensor in the boundary theory. We show that, if treated appropriately, different ways of prescribing asymptotically AdS_3 boundary conditions yield finite conserved charges for the solutions. The consistency of the construction manifests itself in that the charges of hairy asymptotically AdS_3 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 arXiv:1001.3598.

hep-th↗

arXiv2011

Boundary stress tensor and asymptotically AdS3 non-Einstein spaces at the chiral point

Chiral gravity admits asymptotically AdS3 solutions that are not locally equivalent to AdS3; meaning that solutions do exist which, while obeying the strong boundary conditions usually imposed in General Relativity, happen not to be Einstein spaces. In Topologically Massive Gravity (TMG), the existence of non-Einstein solutions is particularly connected to the question about the role played by complex saddle points in the Euclidean path integral. Consequently, studying (the existence of) non-locally AdS3 solutions to chiral gravity is relevant to understand the quantum theory. Here, we discuss a special family of non-locally AdS3 solutions to chiral gravity. In particular, we show that such solutions persist when one deforms the theory by adding the higher-curvature terms of the so-called New Massive Gravity (NMG). Moreover, the addition of higher-curvature terms to the gravity action introduces new non-locally AdS3 solutions that have no analogues in TMG. Both stationary and time-dependent, axially symmetric solutions that asymptote AdS3 space without being locally equivalent to it appear. Defining the boundary stress-tensor for the full theory, we show that these non-Einstein geometries have associated vanishing conserved charges.

hep-th↗

arXiv2011

Deeper discussion of Schrödinger invariant and Logarithmic sectors of higher-curvature gravity

The aim of this paper is to explore D-dimensional theories of pure gravity whose space of solutions contains certain class of AdS-waves, including in particular Schrodinger invariant spacetimes. This amounts to consider higher order theories, and the natural case to start with is to analyze generic square-curvature corrections to Einstein-Hilbert action. In this case, the Schrodinger invariant sector in the space of solutions arises for a special relation between the coupling constants appearing in the action. On the other hand, besides the Schrodinger invariant configurations, logarithmic branches similar to those of the so-called Log-gravity are also shown to emerge for another special choice of the coupling constants. These Log solutions can be interpreted as the superposition of the massless mode of General Relativity and two scalar modes that saturate the Breitenlohner-Freedman bound (BF) of the AdS space on which they propagate. These solutions are higher-dimensional analogues of those appearing in three-dimensional massive gravities with relaxed AdS_3 asymptotic. Other sectors of the space of solutions of higher-curvature theories correspond to oscillatory configurations, which happen to be below the BF bound. Also, there is a fully degenerated sector, for which any wave profile is admitted. We comment on the relation between this degeneracy and the non-renormalization of the dynamical exponent of the Schrodinger spaces. Our analysis also includes more general gravitational actions with non-polynomial corrections consisting of arbitrary functions of the square-curvature invariants. The same sectors of solutions are shown to exist for this more general family of theories. We finally consider the Chern-Simons modified gravity in four dimensions, for which we derive both the Schrodinger invariant as well as the logarithmic sectors.

hep-th↗

arXiv2011

On the addition of torsion to chiral gravity

Three-dimensional gravity in Anti-de Sitter space is considered, including torsion. The derivation of the central charges of the algebra that generates the asymptotic isometry group of the theory is reviewed, and a special point of the theory, at which one of the central charges vanishes, is compared with the chiral point of topologically massive gravity. This special point corresponds to a singular point in Chern-Simons theory, where one of the two coupling constants of the SL(2,R) actions vanishes. A prescription to approach this point in the space of parameters is discussed, and the canonical structure of the theory is analyzed.

hep-th↗

arXiv2010

Disk one-point function for non-rational conformal theories

We consider an infinite family of non-rational conformal field theories in the presence of a conformal boundary. These theories, which have been recently proposed in arXiv:0803.2099, are parameterized by two real numbers (b,m) in such a way that the corresponding central charges c_{b,m} are given by c_{b,m}=3+6(b+b^{-1}(1-m))^{2}. For the disk geometry, we explicitly compute the expectation value of a bulk vertex operator in the case m \in Z, such that the result reduces to the Liouville one-point function when m=0. We perform the calculation of the disk one-point function in two different ways, obtaining results in perfect agreement, and giving the details of both the path integral and the free field derivations.

hep-th↗

arXiv2010

Null geodesics and shadow of a rotating black hole in extended Chern-Simons modified gravity

The Chern-Simons modification to general relativity in four dimensions consists of adding to the Einstein-Hilbert term a scalar field that couples to the first class Pontryagin density. In this theory, which has attracted considerable attention recently, the Schwarzschild metric persists as an exact solution, and this is why this model resists several observational constraints. In contrast, the spinning black hole solution of the theory is not given by the Kerr metric but by a modification of it, so far only known for slow rotation and small coupling constant. In the present paper, we show that, in this approximation, the null geodesic equation can be integrated, and this allows us to investigate the shadow cast by a black hole. We discuss how, in addition to the angular momentum of the solution, the coupling to the Chern-Simons term deforms the shape of the shadow.

gr-qc↗

arXiv2010

Counterterms in semiclassical Horava-Lifshitz gravity

We analyze the semiclassical Hořava-Lifshitz gravity for quantum scalar fields in 3+1 dimensions. The renormalizability of the theory requires that the action of the scalar field contains terms with six spatial derivatives of the field, i.e. in the UV, the classical action of the scalar field should preserve the anisotropic scaling symmetry ($t \to L^{2z}t,$ $\vec{x} \to L^2 \vec{x}$, with $z=3$) of the gravitational action. We discuss the renormalization procedure based on adiabatic subtraction and dimensional regularization in the weak field approximation. We verify that the divergent terms in the adiabatic expansion of the expectation value of the energy-momentum tensor of the scalar field contain up to six spatial derivatives, but do not contain more than two time derivatives. We compute explicitly the counterterms needed for the renormalization of the theory up to second adiabatic order and evaluate the associated $β$ functions in the minimal subtraction scheme.

hep-th↗

arXiv2010

Analytic Lifshitz black holes in higher dimensions

We generalize the four-dimensional R^2-corrected z=3/2 Lifshitz black hole to a two-parameter family of black hole solutions for any dynamical exponent z and for any dimension D. For a particular relation between the parameters, we find the first example of an extremal Lifshitz black hole. An asymptotically Lifshitz black hole with a logarithmic decay is also exhibited for a specific critical exponent depending on the dimension. We extend this analysis to the more general quadratic curvature corrections for which we present three new families of higher-dimensional D>=5 analytic Lifshitz black holes for generic z. One of these higher-dimensional families contains as critical limits the z=3 three-dimensional Lifshitz black hole and a new z=6 four-dimensional black hole. The variety of analytic solutions presented here encourages to explore these gravity models within the context of non-relativistic holographic correspondence.

hep-th↗