arXiv subjects

Gaston Giribet

Publications and source records attributed to Gaston Giribet.

At least 19 recordsLinked to original sources

arXiv2026

Liouville strings in AdS$_3$: the worldsheet story

The worldsheet $σ$-model of strings on AdS$_3$ with NS-NS fluxes can be equivalently described in terms of a Liouville field theory coupled to a timelike field with background charge, plus a marginal deformation. The operator that produces the deformation is non-normalizable and, from the string theory perspective, is associated to the spectral flow sector $ω=2$. Its role is to control the winding number violation in scattering amplitudes. In the semiclassical (large $k$) limit, the central charge of the Liouville factor tends to that of the dual CFT$_2$, namely $c\simeq 6k$. This may appear very similar to what occurs in the Liouville-type description of the dual deformed orbifold CFT$_2$, where a twist-2 deformation operator dressed with a non-normalized field also appears. Indeed, there are some similarities to that; however, there are also significant differences, which we discuss.

hep-th↗

arXiv2026

Neural-Spectral Discovery of Rotating Black Holes Beyond General Relativity

Finding rotating black hole solutions in higher-curvature theories of gravity is a problem of fundamental importance. Virtually every approach to reconcile gravity with quantum mechanics predicts corrections to the Einstein-Hilbert action, yet no systematic solution-generating method exists for the stationary sector. We close this gap with {\sc Akribeia}, a novel hybrid framework that pairs physics-informed neural networks with a pseudo-spectral refinement step, yielding certified neural-field rotating black hole solutions -- continuous, globally defined functions, parametric in the coupling constants -- whose residuals against the field equations are verified to extreme precision. We apply the method to theories quadratic and cubic in the curvature and construct, for the first time, families of rotating black holes featuring multiple non-vanishing angular momenta, parametric in the new coupling constants. After validating against previously known five-dimensional spacetimes, we present new solutions in scenarios leading to a highly non-linear/non-perturbative coupled system of ordinary differential equations. Our method can be systematically adapted to other setups involving partial differential equations as well.

gr-qc↗

arXiv2026

Quark-Antiquark Potential as a Probe for Holographic Phase Transitions

In the recent paper (Phys.Rev.Lett. 133 (2024) 12, 121601), a higher-order phase transition between the planar, charged, 5-dimensional Reissner-Nordström-Anti-de Sitter black hole and a hairy black hole solution of the type IIB supergravity was investigated. Here, following a bottom-up approach, we set out to investigate these two phases of the theory by means of the holographic probe that describes a quark-antiquark in the dual gauge theory. We ask ourselves whether studying the quark-antiquark potential suffices to detect the change of behavior at different values of the parameter that controls the phase transition, this parameter being the ratio between the chemical potential and the temperature. We show that, while evaluating the probe on both phases leads to the same value at the point where the transition takes place, there is always one phase that dominates over the other with regard to this observable. The same can be said about higher-dimensional probes such as those involved in the computation of holographic entanglement entropy.

hep-th↗

arXiv2026

The disk 1-point function in timelike Liouville theory

We compute the disk 1-point function in timelike Liouville theory. Using the Coulomb gas formalism and analytically continuing in the number of screening operators, we derive an explicit formula, which is shown to satisfy the correct reflection symmetry, to have the expected self-dual properties, to fulfill the bootstrap shift-equations, and to reduce to previous known results in the appropriate limits. In the limit of zero cosmological constant, our result reproduces the one recently obtained in arXiv:2505.09390.

hep-th↗

arXiv2025

Revisiting a family of five-dimensional charged, rotating black holes

In the absence of a higher-dimensional analogue to the Kerr-Newman black hole, 5-dimensional Einstein-Maxwell theory with a Chern-Simons term has become a natural setting for studying charged, stationary solutions. A prominent example is the Chong-Cvetič-Lü-Pope (CCLP) solution, which describes a non-extremal black hole with electric charge and two independent angular momenta. This solution has been widely studied, and generalizations have been proposed. In this paper, we revisit a large family of five-dimensional black hole solutions to Einstein-Maxwell-Chern-Simons (EMCS) field equations, which admits to be written in terms of a generalized Plebański-Demiański ansatz and includes the CCLP and the Kerr-NUT-Anti-de Sitter solutions as particular cases. We show that the complete family can be brought to the CCLP form by means of a suitable coordinate transformation and a complex redefinition of parameters. Then, we compute the conserved charges associated to the CCLP form of the metric by analyzing the near-horizon asymptotic symmetries. We show that the zero-mode of the near-horizon charges exactly match the result of the Komar integrals.

hep-th↗

arXiv2025

Higher-curvature corrections and near horizon symmetries

In the near-horizon region, black holes exhibit an infinite-dimensional symmetry reminiscent of the Bondi-Metzner-Sachs (BMS) supertranslations. The conserved charges associated with this symmetry can be computed in gravitational theories of arbitrary spacetime dimension and involving curvature terms of any order. In Lovelock theory, for instance, these charges take the form of nested Lagrangian densities corresponding to topological invariants, each weighted by the supertranslation function -- thus providing a natural generalization of the Wald entropy formula. In four dimensions, the computation of the supertranslation charge reduces to the evaluation of the Jackiw-Teitelboim (JT) action on the two-dimensional spacelike sections of the event horizon.

hep-th↗

arXiv2025

Exploring the Kleinian horizons

Self-dual black holes in (2,2) signature spacetime -- Klein space -- have recently attracted interest in the context of celestial holography. Motivated by this development, we investigate the structure of spacetime near the horizons of these solutions. Focusing on the self-dual Schwarzschild-Taub-NUT solution, we demonstrate that, near the Kleinian horizons, the geometry exhibits a local infinite-dimensional symmetry generated by supertranslations and superrotations. Establishing this result requires refining and extending earlier analyses of asymptotic symmetries near null surfaces. We formulate the appropriate boundary conditions, derive the infinite-dimensional algebra underlying the local symmetries, and compute the associated Noether charges, finding them to be integrable. Finally, we discuss the connection of our findings to recent observations in the literature regarding self-dual black holes in Klein space, including the diffeomorphism relating static and stationary solutions.

hep-th↗

arXiv2025

Celestial closed strings at one-loop

In this paper we continue our investigation of superstring scattering amplitudes in the conformal basis. We focus on the case of four graviton scattering processes at 1-loop in \emph{closed} superstring theory. We write the expression for such a process in the celestial variables and confirm previous expectations. In particular, we find the adequate overall factorization of the $α'$ dependence which organizes the loop expansion of closed string celestial amplitudes. We also show that, at 1-loop, the field theory limit, when properly defined, commutes with the Mellin transform of the amplitudes for all values of the conformally invariant cross-ratio, something that had already been observed for gluon processes at 1-loop in open string theory and is to be compared with the tree-level computations. This indicates that many of the features satisfied for open string gluon amplitudes at tree and 1-loop levels are also universal properties of graviton celestial amplitudes in closed string theory. As a by-product, we also compute field theory graviton amplitudes at 1-loop in the conformal basis.

hep-th↗

arXiv2025

Deforming the Double Liouville String

We consider a generalization of the double Liouville theory, which can be thought of as a two-parameter family of marginal deformations of the so-called Virasoro Minimal String (VMS). The latter consists of a timelike ($c_{-}<1$) and a spacelike ($c_{+}>25$) Liouville field theory formulated on a fluctuating Riemann surface. For the deformed theory, we compute the sphere partition function exactly in $1/c_{\pm}$ and at third order in the coupling constant ($λ$) that controls the deformation. We also discuss the analogous computation in the case of the Complex Liouville String (CLS) theory, which is defined as two spacelike Liouville theories with complex central charges $c_{\pm }=13\pm i\mathbb{R}_{>0}$. We show that the partition functions of VMS and CLS differ at leading order in $λ$ due to the presence of elliptic functions in the observables of the latter. Both VMS and CLS theories have recently been studied in relation to many interesting models, including the double scaled Sachdev-Ye-Kitaev model, matrix models, and de Sitter gravity in 2 and 3 dimensions. We comment on the interpretation of the marginal deformation in some of these contexts.

hep-th↗

arXiv2025

BPS defects in AdS$_{3}$ supergravity

AdS supergravity admits supersymmetric solutions that describe BPS defects. Here, we investigate such solutions in AdS$_3$ supergravity, which is formulated as a Chern-Simons theory on $\mathrm{OSp}(2|1)\,\times\, \mathrm{OSp}(2|1)$. We compute the Killing spinor equation on the BTZ geometry in different ways, looking for BPS solutions on the entire space of parameters. We focus our attention on defects that represent geometries with integer angular excesses; these correspond to specific negative values of the BTZ mass. We compare our solutions with other results in the literature, finding exact agreement. We argue that, in the semiclassical limit, the BPS defects can be associated to degenerate representations of the Virasoro symmetry at the boundary. The case of non-diagonal representations, describing stationary, non-static defects, is also discussed.

hep-th↗

arXiv2025

MHV leaf amplitudes from parafermions

We give a dual CFT representation of MHV leaf amplitudes in the large $N$ and semiclassical limit in terms of non-compact parafermions and a single affine Kac-Moody current for $SO(N)$. This representation is consistent with the other 2D CFT realization of 4D leaf amplitudes proposed in the literature, which is based on a dressed Liouville theory. The equivalence between the two CFT descriptions arises from the $H_3^+$ WZW-Liouville correspondence, applied to the $SL(2,\mathbb{R})/U(1)$ coset theory in the spectrally flowed sector.

hep-th↗

arXiv2024

On the $AdS_3$ Virasoro-Shapiro Amplitude

We consider tree-level scattering amplitudes for four string tachyons on $AdS_3 \times {\cal N}$ with pure NSNS fluxes. We show that in a small curvature expansion, properly defined, the amplitudes take the form of a genus zero integral given by the Virasoro-Shapiro integrand with the extra insertion of single valued multiple polylogarithms. This is the same structure as the one found for the AdS Virasoro-Shapiro amplitude in higher dimensions.

hep-th↗

arXiv2024

Jackiw-Teitelboim Gravity as a Noncritical String

Jackiw Teitelboim (JT) gravity has proven to be an excellent tool for investigating aspects of quantum gravity and black hole physics. In recent years, the study of JT gravity and its deformations has helped us learn about the different contributions of geometries in the gravitational path integral, the quantum gravity Hilbert space, the space-time factorization problem, the role of averaging in holography, the black hole information paradox, and the matrix models. All this motivates the exploration of the JT gravity in different setups, with and without matter. Here, we consider JT gravity conformally coupled to Liouville field theory and matter fields. This model admits to be interpreted as a non-critical string theory on a linear dilaton background with a tachyonic Liouville potential along a null direction. The constant curvature constraint of JT gravity results in a neutralization of the Liouville mode, which makes it possible to compute the four-point correlation function of the theory analytically. Here we give the explicit derivation of the four-point function and briefly comment on its properties, such as monodromy invariance, crossing symmetry, factorization, and limits.

hep-th↗

arXiv2024

Higher-curvature gravity in AdS$_3$, holographic $c$-theorems and black hole microstates

We construct higher-derivative gravity theories in three dimensions that admit holographic $c$-theorems and exhibit a unique maximally symmetric vacuum, at arbitrary order $n$ in the curvature. We show that these theories exhibit special properties, the most salient ones being the decoupling of ghost modes around Anti-de Sitter (AdS) space, the enhancement of symmetries at linearized level, and the existence of a one-parameter generalization of the Bañados-Teitelboim-Zanelli (BTZ) black hole that, while being asymptotically AdS, is not of constant curvature but rather exhibits a curvature singularity. For such black holes, we provide a holographic derivation of their thermodynamics. This gives a microscopic picture of black hole thermodynamics for non-supersymmetric solutions, of non-constant curvature in higher-derivative theories of arbitrary order in the curvature.

hep-th↗

arXiv2024

Celestial strings: field theory, conformally soft limits, and mapping the worldsheet onto the celestial sphere

We compute the celestial correlators corresponding to tree-level 5-gluon amplitudes in the type I superstring theory. Since celestial correlation functions are obtained by integrating over the full range of energies, there is no obvious analog of the $α' \to 0$ limit in this basis. This is manifestly shown by a factorization of the $α'$ dependence in the celestial string amplitudes. Consequently, the question arises as to how the field theory limit is recovered from string theory in the celestial basis. This problem has been addressed in the literature for the case of 4-gluon amplitudes at tree level, where the forward scattering limit of the stringy factor was identified as a limit in which celestial Yang-Mills 4-point function is recovered. Here, we extend the analysis to the case with five gluons, for which the string moduli space allows for more types of limits, thus allowing to investigate this aspect in more detail. Based on celestial data only, we study the regime in which one arrives at the correct celestial field theory limit. We also study other properties of the celestial string amplitudes, namely, the conformally soft theorem, effective field theory expansion in the conformal basis, and a map that arises in the regime of high-energy/large-scaling dimension that connects the punctured string worldsheet to the insertion of primary operators in the celestial CFT for the massless $n$-point string amplitude.

hep-th↗

arXiv2024

Overflying Nilpotent Horizons

We study solutions of Einstein equations with negative cosmological constant in five dimensions that describe black holes whose event horizons are homogeneous, anisotropic spaces. We focus on the case where the constant-time slices of the horizon are the Nil geometry, the Thurston geometry associated to the Heisenberg group. For such spaces, we analyze the symmetries both in the asymptotic region and in the near horizon region. We compute the associated conserved charges, which turn out to be finite and admit a sensible physical interpretation. We analyze the thermodynamics of the Nil black hole, and we present a stationary spinning generalization of it in the slowly rotating approximation.

hep-th↗

arXiv2024

Quantum backreactions in (A)dS3 massive gravity and logarithmic asymptotic behavior

We study the interplay between higher curvature terms and the backreaction of quantum fluctuations in 3-dimensional massive gravity in asymptotically (Anti-)de Sitter space. We focus on the theory at the special point of the parameter space where the two maximally symmetric vacua coincide. In the case of positive cosmological constant, this corresponds to the partially massless point, at which the classical theory admits de Sitter black holes and exhibits an extra conformal symmetry at linear level. We explicitly find the quantum corrected black hole geometry in the semiclassical approximation and show that it induces a relaxation of the standard asymptotic conditions. Nonetheless, the new asymptotic behavior is still preserved by an infinite-dimensional algebra, which, in addition to Virasoro, contains logarithmic supertranslations. Finally, we show that all the results we obtain for the quadratic massive gravity theory can be extended to theories including cubic and quartic terms in the curvature.

hep-th↗

arXiv2024

Remarks on celestial amplitudes and Liouville theory

The relation between celestial holography and Liouville field theory is investigated. It is shown that duality relations between different Selberg type integrals appearing in the Coulomb gas realization of Liouville correlation functions induce a series of relations between celestial amplitudes with shifted values of the operators dimensions $Δ$. This is a transcript of the talk delivered by the author at the Workshop on Celestial Holography and Asymptotic Symmetries, Santiago de Chile, March 4-6, 2024.

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