arXiv subjects

José Manuel Penín

Publications and source records attributed to José Manuel Penín.

13 recordsLinked to original sources

arXiv2026

Holographic surface defect RG flows without supersymmetry

We consider $\mathcal{N}=4$ supersymmetric Yang--Mills theory with gauge group SU$(N)$, which admits families of conformal surface defects defined by singular boundary conditions for scalar fields that completely break supersymmetry. At large $N$ and strong coupling, these defects are holographically dual either to a probe D5-brane or to one of two new D7-brane embeddings that we introduce in this work. We also construct embeddings of both D5- and D7-branes describing defect renormalisation group (RG) flows, for which the ultraviolet and infrared fixed points are both dual to the same D$p$-brane, with different values of a parameter. Our embeddings dual to RG flows are mostly constructed numerically, but we find a regime in which we can derive approximate analytic embeddings using a controlled perturbative expansion. We demonstrate that the $b$-theorem is satisfied by all of the RG flows that we study.

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arXiv2026

Entanglement C-functions of defects and interfaces in $\mathcal{N}=4$ supersymmetric Yang-Mills theory

We consider planar codimension-one defects and interfaces in $\mathcal{N}=4$ supersymmetric Yang-Mills (SYM) theory, realized by the D3/D5-brane intersection. Working in the probe limit, where the number of D5-branes is small compared to the number of D3-branes, we obtain analytic results for the holographic entanglement entropy of a ball-shaped region centered on the defect. A defect renormalization group flow is triggered by giving the defect hypermultiplets a mass, which corresponds to separating the D3- and D5-branes. Along this flow the entanglement C-function decreases monotonically. We also allow the D5-branes to carry worldvolume flux corresponding to dissolved D3-branes, in which case the setup describes an interface between two copies of $\mathcal{N}=4$ SYM theory with different gauge groups, where an RG flow is triggered by placing one side of the interface onto the Coulomb branch. Here we again find monotonic behavior of the entanglement C-function, although its interpretation as a measure of effective degrees of freedom is problematic. We investigate possible alternative measures of degrees of freedom.

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arXiv2026

Covariant unification of holographic c-functions

We propose a covariant holographic c-function, defined directly in a top-down background and constructed from the extrinsic curvature of codimension-two slices of the bulk geometry. The definition does not rely on a special choice of coordinates or on the existence of a consistent dimensional reduction. We show that it unifies previous foliation-based holographic c-functions into a single covariant formula, reducing to them in the appropriate limits. We evaluate the covariant expression in a range of top-down string backgrounds, including conformal models, confining geometries, flows across dimensions, and the Klebanov-Murugan geometry, in which the holographic radial direction mixes with internal coordinates and which is not the uplift of a lower-dimensional solution. In all cases, the c-function behaves as expected: it interpolates monotonically between AdS fixed points when they are present and decreases towards zero in gapped infrared regions, while in the Klebanov-Murugan case we recover the correct fixed-point values and find evidence for monotonicity. We highlight open conceptual issues, including: the lack of a universal covariant definition of the holographic radial direction in the presence of a nontrivial internal manifold; the derivation of the flow from a bulk action; and the relation to the entanglement c-function.

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arXiv2025

On entanglement c-functions in confining gauge field theories

Entanglement entropy has proven to be a powerful tool for probing renormalization group (RG) flows in quantum field theories, with c-functions derived from it serving as candidate measures of the effective number of degrees of freedom. While the monotonicity of such c-functions is well established in many settings, notable exceptions occur in theories with a mass scale. In this work, we investigate entanglement c-functions in the context of holographic RG flows, with a particular focus on flows across dimensions induced by circle compactifications. We argue that in spacetime dimensions $d \geq 4$, standard constructions of c-functions, which rely on higher derivatives of the entanglement entropy of either a ball or a cylinder, generically lead to non-monotonic behavior. Working with known dual geometries, we argue that the non-monotonicity stems not from any pathology or curvature singularity, but from a transition in the holographic Ryu--Takayanagi surface. In compactifications from four to three dimensions, we propose a modified construction that restores monotonicity in the infrared, although a fully monotonic ultraviolet extension remains elusive. Furthermore, motivated by entanglement entropy inequalities, we conjecture a bound on the cylinder entanglement c-function, which holds in all our examples.

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arXiv2025

Holographic Hagedorn Temperature: Strong Coupling, Flavor and $θ$-angle Effects

We study the Hagedorn temperature $T_H$ of strongly coupled quantum field theories admitting a holographic string or M-theory description in various regimes and scenarios. In the first part of the paper we propose a ``thermal scalar'' effective approach to the calculation of $T_H$ in eleven-dimensional supergravity. The proposal allows to extend the existing results for $T_H$ to the strongly coupled string regime, i.e. to a previously unexplored regime of field theory parameters where the number of colors $N$ is smaller than (some power of) the 't Hooft coupling $λ$. We can thus extend the existing results for the $α'$ expansion of the ABJM model, which have a spectacular agreement with predictions from integrability, in a different direction in parameter space. In particular, we explicitate the first non-perturbative corrections. We also apply the formalism to the Witten-Yang-Mills model, finding that the result for the ratio of $T_H$ with the deconfinement temperature is in the same ballpark of the lattice one for pure Yang-Mills. Within the same model, we study the dependence of the Hagedorn temperature on the $θ$-angle. In the second part of the paper we analyze the effect of dynamical flavors on $T_H$ in confining theories. By studying the few available examples of regular backgrounds dual to confining theories with flavors, we find that generally the effects of flavors is to reduce the value of $T_H$ in units of the square root of the confining string tension. The effect turns out to be milder than the analogous reduction of the critical temperature for deconfinement when the latter is known.

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arXiv2024

Evidence for a $4$-dimensional $\mathcal{N}=1$ integrable quiver in massive type IIA

We are examining a newly discovered parametric family of backgrounds in massive type IIA supergravity that contains a warped $\text{AdS}_5$ factor. This family is the dual gravity description of $4$-dimensional quivers with $\mathcal{N}=1$ supersymmetry. We are interested in the status of classical integrability in these theories and we show that there exists a single choice of solutions that is special, while all other choices lead to non-integrable quivers and chaotic string motion. By focusing on this special choice we provide strong suggestive evidence for the integrability of the dual field theory based on analytic studies and extensive numerical analysis.

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arXiv2024

Flavors of entanglement

We employ holography to investigate Liu-Mezei renormalization group monotones in conformal field theories influenced by massive flavor degrees of freedom. We examine the entanglement entropy of a spherical subregion in three holographic field theories - $\mathcal{N}=1$ Klebanov-Witten theory, $\mathcal{N}=4$ SYM theory, and ABJM theory - with fundamental flavor. The gravity dual of massive unquenched flavor is described by dynamical D-branes, and we solve their backreaction in the smeared approximation. We compute entanglement entropy using the Ryu-Takayanagi formula in these backreacted geometries. Our findings indicate that the Liu-Mezei A- and F-functions decrease monotonically to leading order in the number of flavors across all examples. Additionally, we calculate the leading flavor contribution to entanglement entropy using an alternative probe brane method that does not require knowledge of backreaction in the bulk geometries. These results consistently match with backreacted calculations in all cases, assuming omission of a specific IR boundary term stemming from a total derivative.

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arXiv2022

Flavored anisotropic black holes

We construct a black hole geometry dual to a (2+1)-dimensional defect in an ambient (3+1)-dimensional gauge theory at non-zero temperature and quark density. The geometry is a solution to the equations of motion of type IIB supergravity with brane sources, a low energy limit of an intersection of stacks of color D3-branes and flavor D5-branes. We consider the case in which the number of D5-branes is large and they can be homogeneously distributed along the directions orthogonal to the defect, creating in this way a multilayer structure. The quark density is generated by exciting a gauge field in the worldvolume of the dynamic brane sources. We study the thermodynamics of the anisotropic black hole and compute the energy density of the dual theory, as well as the pressures and speeds of sound along the directions parallel and orthogonal to the defect. We also calculate transport coefficients in the shear channel, quark-antiquark potentials, and the entanglement entropies for slab subregions. These analyses give us a good overview on how the degrees of freedom are spread, entangled, and behave in this unquenched system in the deconfining phase at strong coupling.

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arXiv2022

Massive holographic QFTs in de Sitter

We study strongly coupled mass-deformed-CFT on a fixed de Sitter spacetime in three dimensions via holography. We elucidate the global causal structure of the four-dimensional spacetime dual to the de Sitter invariant vacuum state. The conformal boundaries of de Sitter appear as spacelike defects sourced by the mass deformation, which extend into the bulk as curvature singularities in AdS. We compute all one- and two-point functions of the deformed-CFT stress tensor and a scalar operator order-by-order in the mass deformation for a simple holographic model. These correlation functions admit a spectral representation as a sum of simple poles corresponding to normalisable modes in the bulk.

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arXiv2022

Gravity duals for defect quivers in the Veneziano limit

We construct gravity duals to supersymmetric gauge theories in the presence of unquenched flavor hypermultiplets in the fundamental representation of the gauge group living on the (1+1)-dimensional defect. This configuration is given by the intersection of two sets of D3-branes. Working in the Veneziano limit with large number of colors and flavors we are able to find a closed set of equations describing the dual geometry. We briefly discuss the corresponding solutions for massless flavors as well as in the small flavor limit of massive hypermultiplets. Interestingly, the 1/4-BPS supergravity solutions are generically only asymptotically anti de-Sitter, the dilaton does not vary with the holographic radial coordinate. This implies that the classical Type IIB supergravity solutions remain trustworthy descriptions for the gauge theories from the deep IR to the far UV.

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arXiv2020

Holographic spontaneous anisotropy

We construct a family of holographic duals to anisotropic states in a strongly coupled gauge theory. On the field theory side the anisotropy is generated by giving a vacuum expectation value to a dimension three operator. We obtain our gravity duals by considering the geometry corresponding to the intersection of D3- and D5- branes along 2+1 dimensions. Our backgrounds are supersymmetric and solve the fully backreacted equations of motion of ten-dimensional supergravity with smeared D5-brane sources. In all cases the geometry flows to $AdS_{5}\times {\mathbb S}^5$ in the UV, signaling an isotropic UV fixed point of the dual field theory. In the IR, depending on the parameters of the solution, we find two possible behaviors: an isotropic fixed point or a geometry with anisotropic Lifshitz-like scaling symmetry. We study several properties of the solutions, including the entanglement entropy of strips. We show that any natural extension of existing $c$-functions will display non-monotonic behavior, conforming with the presence of new degrees of freedom only at intermediate energy scales.

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arXiv2019

Spin-2 excitations in Gaiotto-Maldacena solutions

In this paper we study spin-2 excitations for a class of $\mathcal{N} = 2$ supersymmetric solutions of type-IIA supergravity found by Gaiotto and Maldacena. The mass spectrum of these excitations can be derived by solving a second order partial differential equation. As specific examples of this class we consider the Abelian and non-Abelian T-dual versions of the $AdS_5 \times S^5$ and we study the corresponding mass spectra. For the modes that do not "feel" the (non-)Abelian T-duality transformation we provide analytic formulas for the masses, while for the rest we were only able to derive the spectra numerically. The numerical values that correspond to large masses are compared with WKB approximate formulas. We also find a lower bound for the masses. Finally, we study the field theoretical implications of our results and propose dual spin-2 operators.

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arXiv2015

An analysis of the impact of LHC Run I proton-lead data on nuclear parton densities

We report on an analysis of the impact of available experimental data on hard processes in proton-lead collisions during Run I at the Large Hadron Collider on nuclear modifications of parton distribution functions. Our analysis is restricted to the EPS09 and DSSZ global fits. The measurements that we consider comprise production of massive gauge bosons, jets, charged hadrons and pions. This is the first time a study of nuclear PDFs includes this number of different observables. The goal of the paper is twofold: i) checking the description of the data by nPDFs, as well as the relevance of these nuclear effects, in a quantitative manner; ii) testing the constraining power of these data in eventual global fits, for which we use the Bayesian reweighting technique. We find an overall good, even too good, description of the data, indicating that more constraining power would require a better control over the systematic uncertainties and/or the proper proton-proton reference from LHC Run II. Some of the observables, however, show sizable tension with specific choices of proton and nuclear PDFs. We also comment on the corresponding improvements on the theoretical treatment.

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