arXiv subjects

Edwan Préau

Publications and source records attributed to Edwan Préau.

10 recordsLinked to original sources

arXiv2026

Near-extremal hydrodynamics and the holographic product formula

The holographic product formula is used to determine the general form taken by holographic spectral functions in the near-extremal hydrodynamic regime, with energy $ω$, momentum $k$ and temperature $T$ much smaller than a hard scale $μ$. The resulting expressions simplify in the extremal limit $T \ll ω,k\ll μ$, for which the low-temperature gapless modes and the IR conformal behavior factorize. In some cases, this factorization extends to the general near-extremal regime $ω,k,T\llμ$ at leading order in $T/μ$. Several examples are discussed with different types of gapless modes and IR CFTs, including new numerical results for low temperature quasi-normal modes. We end with a concrete application that shows how the inclusion of the IR conformal behavior improves the description of the spectral function at low energies.

hep-th↗

arXiv2026

Holographic zeros and poles from apparent singularities

We study general holographic fluctuation equations with apparent singularities, and the associated spectral functions. We consider the regime where an apparent singularity approaches the boundary, for which the near-boundary behavior of solutions can be determined via an inner/outer matching type of calculation. Depending on properties of the equation, we find that the merging of an apparent singularity with the boundary may generate either a zero or a pole for the corresponding spectral function. Our results also indicate that the recently introduced holographic product formula still applies in the presence of apparent singularities.

hep-th↗

arXiv2026

$O(d,d)$ symmetric gravity and finite coupling holography

We construct asymptotically AdS$_5$ black brane solutions in a theory of gravity with an infinite series of curvature corrections. The action is based on an $O(d,d)$ symmetric ansatz which has been argued to describe the classical NSNS sector of string theories. We find that, for this general class of theories, the singularity behind the horizon is not resolved by the curvature corrections. The approach to the singularity is however generically modified, being characterized by different Kasner exponents. We also show that, in the presence of a non-trivial dilaton, a slight generalization of these types of curvature corrections can generate dynamically a negative cosmological constant in the region of small coupling. This provides a mechanism through which asymptotic freedom could emerge in the hypothetical string dual of QCD.

hep-th↗

arXiv2026

The Tachyon Chern-Simons action with a generic tachyon field, and baryons in V-QCD

Consistency with global flavor anomalies requires the presence of Chern-Simons terms in holographic models of QCD. Such terms are analyzed in a setup arising in the holographic V-QCD model, where chiral symmetry breaking is implemented through the condensation of a complex scalar field, the tachyon. Using the superconnection formalism, the Tachyon-Chern-Simons terms are constructed explicitly in the general case, where the tachyon is any complex matrix in flavor space. This general case covers, among other things, backgrounds where different quark flavors have different masses. These new results are used to analyze the structure of the baryon solutions in the presence of nonzero quark masses. Expressions for the baryon number current and the total baryon number are found, and the baryon number is shown to be equal to the topological instanton number of the baryon solution. The effective four-dimensional pion action is analyzed and is shown to reproduce the chiral Lagrangian, including the Skyrme and Wess-Zumino-Witten terms.

hep-th↗

arXiv2026

Flavour current correlators and the non-Abelian hydrodynamic approximation: the charged sector

Flavor-current correlators are studied in strongly-coupled dense (holographic) matter, at finite quark chemical potential $μ_q$ and finite isospin asymmetry. The non-Abelian hydrodynamic description of the charged currents is derived in the presence of an isospin chemical potential $μ_3$. The two-point correlators of charged currents are then computed holographically at finite quark and isospin chemical potentials. In the near-extremal hydrodynamic regime, $ω, k, T, μ_3 \ll μ\equiv \sqrt{μ_q^2+μ_3^2}$, relevant for cold strongly coupled matter, the IR properties of the correlators are studied. It is shown that in this regime, the correlators agree with the non-Abelian hydrodynamic predictions. Therefore, the traditional regime of validity of standard hydrodynamics extends beyond $ω, k \ll T \ll μ$ to the so-called extended hydrodynamic regime $T\ll ω, k \ll μ$. The holographic product formula is applied to the present non-Abelian system, and is used to propose an extended hydrodynamic approximation capturing both hydrodynamic-like poles and the leading effect of AdS$_2$ poles, by resumming the low-$ω$ logarithms. The results are verified through a detailed numerical analysis of the exact correlators and quasi-normal mode spectrum.

hep-th↗

arXiv2025

Higher derivative holography and temperature dependence of QGP viscosities

Recent Bayesian analyses of heavy ion collision data have established a non-trivial temperature dependence of the shear and bulk viscosity per entropy. Motivated by this, we consider higher derivative corrections to realistic, bottom-up holographic models of quark-gluon plasma based on five-dimensional Einstein-dilaton theories and determine the dilaton potentials in the higher derivative terms by matching the Bayesian analyses. A byproduct of our analysis is the bulk viscosity that follows from the holographic V-QCD theory. Higher derivative corrections when treated perturbatively lead to tension with existing data. We investigate possible resolutions.

hep-th↗

arXiv2025

Revisiting color superconductors in bottom-up holography

We revisit the problem of constructing a color superconducting phase in bottom-up holography. We introduce a model that describes the five-dimensional dynamics of a scalar field dual to a chiral symmetry breaking condensate, which is coupled to the RR 4-form. The coupling is given by a topological WZ term, which is elegantly responsible both for scalar condensation at high density, and color Higgsing in the condensed phase. This construction realizes both properties at finite density and Higgsing fraction.

hep-th↗

arXiv2024

Phases and Phase transitions of U(1)$\times$SU(2) symmetric holographic matter

The phase diagram and symmetry breaking patterns of a holographic CFT with U(1)$\times$SU(2) symmetry are analyzed using the simplest holographic action, namely Einstein-Yang-Mills (YM) theory with a negative cosmological constant. This is relevant for both condensed matter and QCD applications. With a U(1) and an "isospin" chemical potential turned on, we determine all possible symmetry breaking patterns, which are associated to the condensation of spin-one order parameters. The possible IR asymptotics of the Einstein-YM solutions are derived analytically, both for 2+1 and 3+1 boundary dimensions. The competing solutions are then computed numerically, both at zero and non-zero temperature, from which the full three-dimensional phase diagram is determined. We find a surface of second order phase transitions that separate uncondensed and condensed phases. In some regions with a large fraction of charged to neutral degrees of freedom, the phase transition becomes first order.

hep-th↗

arXiv2021

Neutron conversion-diffusion: a new model for structured short gamma-ray burst jets compatible with GRB 170817

We present a generic theoretical model for the structuring of a relativistic jet propagating through the ejecta of a binary neutron star merger event, introducing the effects of the neutron conversion-diffusion, which provides a baryon flux propagating transversely from the ejecta towards the jet axis. This results naturally in an increased baryon load structure of the outer jet with the approximate isotropic energy distribution $E_{iso}(θ) \propto θ^{-4}$, which is compatible with the first gravitational wave and short gamma-ray burst event GW170817/GRB 170817A observed at an off-axis angle of the jet.

astro-ph.HE↗

arXiv2020

Holographic QFTs on S$^2\times $S$^2$, spontaneous symmetry breaking and Efimov saddle points

Holographic CFTs and holographic RG flows on space-time manifolds which are $d$-dimensional products of spheres are investigated. On the gravity side, this corresponds to Einstein-dilaton gravity on an asymptotically $AdS_{d+1}$ geometry, foliated by a product of spheres. We focus on holographic theories on $S^2\times S^2$, we show that the only regular five-dimensional bulk geometries have an IR endpoint where one of the sphere shrinks to zero size, while the other remains finite. In the $Z_2$-symmetric limit, where the two spheres have the same UV radii, we show the existence of a infinite discrete set of regular solutions, satisfying an Efimov-like discrete scaling. The $Z_2$-symmetric solution in which both spheres shrink to zero at the endpoint is singular, whereas the solution with lowest free energy is regular and breaks $Z_2$ symmetry spontaneously. We explain this phenomenon analytically by identifying an unstable mode in the bulk around the would-be $Z_2$-symmetric solution. The space of theories have two branches that are connected by a conifold transition in the bulk, which is regular and correspond to a quantum first order transition. Our results also imply that $AdS_5$ does not admit a regular slicing by $S^2\times S^2$.

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