arXiv subjects

Roldao da Rocha

Publications and source records attributed to Roldao da Rocha.

At least 19 recordsLinked to original sources

arXiv2026

Coherent quantum hairy black holes from gravitational decoupling: regularity, geodesics, and scalar ringdown

We construct a coherent-state quantum extension of gravitational-decoupling (GD) hairy black holes, in which the classical spacetime geometry emerges as the mean-field limit of a finite graviton condensate, while quantum fluctuations provide a natural short-distance regulator. The coherent quantum GD hairy black hole metric is obtained by Gaussian smearing of the gravitational potential, with an effective width encoding the size of the quantum core. The resulting geometry is free of curvature singularities over appropriate parameter ranges and exhibits a modified horizon structure. We also investigate geodesic motion in the coherent quantum GD hairy spacetime and find significant deviations from the classical Reissner-Nordström (RN) geometry. In particular, the photon ring, critical impact parameter, and light deflection are modified by the combined effects of quantum corrections and GD hair, providing potential strong-field tests of deviations from general relativity. Finally, we employ the WKB approximation to show that the coherent quantum GD hairy black hole has a quasinormal mode spectrum that differs from those of both the classical GD hairy and Schwarzschild black holes.

hep-th↗

arXiv2026

Phase transitions at high and low densities for a rotating QCD matter from holography

We applied the exact Andreev soft-wall holographic model to investigate phase transitions in rotating strongly interacting matter at high and low densities. Using the dual description of hadronic matter and quark-gluon plasma via thermal and charged black holes in five-dimensional AdS space with cylindrical symmetry, we find that for relativistic rotations exceeding 16\% of the speed of light, crossover transitions emerge in the low-density regime up to a critical baryon chemical potential $μ_{CPB}$. These smooth transitions, governed by the negative QCD $β$-function, describe a mixed phase of confined and deconfined matter with different angular momenta evolving into a pure plasma at very high temperatures. For $μ\geq μ_{CPB}$, first-order transitions dominate, following the critical-temperature curve of non-rotating matter. The critical point separating the low-density crossovers from high-density first-order transitions is numerically estimated as $(μ_{CPB}, T_{CP}) = (363.554, 58.507)\,\text{MeV}$.

nucl-th↗

arXiv2026

Hairy black hole solutions in nonlocal quadratic gravity

Hairy black hole solutions are constructed within quantum-inspired nonlocal quadratic gravity. Nonlocal effects induce Yukawa screening, which shifts the event horizon inward and modifies both the Bekenstein--Hawking entropy and the Hawking temperature, while also renormalizing the chemical potential. Nonlocal corrections also reduce the magnitude of the negative specific heat, making small hairy black holes more stable, with Helmholtz and Gibbs free energies consistent with the absence of first-order phase transitions. The nonlocal spin-2 propagator contains, in addition to the massless graviton, a massive pole with positive residue and positive norm. Consequently, hairy black holes in nonlocal quadratic gravity are free of ghost instabilities at the quadratic and classical levels, in the effective field theory.

hep-th↗

arXiv2025

Confinement/deconfinement at low temperatures and rotation in the exact soft wall model

We study the effects of rotation on the confinement/deconfinement phase transition of strongly interacting matter, at low temperatures, in the soft wall AdS/QCD model at finite density. To achieve it, we apply the Hawking-Page approach to the exact Andreev's solution of a charged rotating black hole in five-dimensional AdS space. We observe that there is a critical angular velocity ($ω_0$) of hadronic matter that depends on the baryon density, representing a strong constraint on the rotation in hadronic matter. We obtain the curve $ω_0(μ)$, which shows that the critical rotational velocity allowed for hadronic matter decreases as the chemical potential ($μ$) increases. When $μ$ approaches the most critical quark chemical potential, identified as the density of a phase transition at zero temperature for a non-rotating plasma, the rotational velocity allowed for the hadrons tends to zero. If $ω\geq ω_0 $, there is no phase transition and the QCD matter remains in the deconfined plasma phase. The QCD phase diagram is also obtained for the exact solution, and the critical temperatures are compared with the ones obtained from the Reissner-Nordström approximation. The results are interpreted as a consequence of contributions from regions relatively distant from the AdS boundary, which cause a non-negligible reduction in the deconfinement temperatures.

hep-th↗

arXiv2025

Holographic QCD model for heavy and exotic mesons at finite density: A self-consistent dynamical approach

We present a self-consistent dynamical holographic QCD model to investigate the mass spectra and melting behavior of heavy and exotic mesons at finite temperature and finite density. Our approach is based on the Einstein-Maxwell-Dilaton (EMD) framework and incorporates an elsewhere already introduced, albeit by hand, phenomenological non-quadratic dilaton profile. This allows one to capture the non-linear Regge trajectories of heavy-flavor mesons and model certain exotic states. We show how to construct such models by actually solving the coupled Einstein, Maxwell, and dilaton field equations, ensuring mathematical self-consistency to replace any ad-hoc input. At finite temperature, we analyze the confinement-deconfinement transition via a Hawking-Page phase transition. We compute the spectral functions, revealing the sequential melting of quarkonia as the temperature is increased. Extending to finite density, we explore the impact of baryon chemical potential on meson stability, showing significant modifications in spectral peaks and effective potentials that indicate a more rapid melting of mesonic states as the chemical potential increases in the deconfined phase. The dual of the small/large black hole transition now indicates towards a first order phase transition line ending at a second order critical point. Interestingly, the spectral functions smoothly cross this phase transition line.

hep-th↗

arXiv2025

Algebraic solutions for $SU(2)\otimes SU(2)$ Hamiltonian eigensystems: generic statistical ensembles and a mesoscopic system application

Solutions of generic $SU(2)\otimes SU(2)$ Hamiltonian eigensystems are obtained through systematic manipulations of quartic polynomial equations. An {\em ansatz} for constructing separable and entangled eigenstate basis, depending on the quartic equation coefficients, is proposed. Besides the quantum concurrence for pure entangled states, the associated thermodynamic statistical ensembles, their partition function, quantum purity and quantum concurrence are shown to be straightforwardly obtained. Results are specialized to a $SU(2)\otimes SU(2)$ structure emulated by lattice-layer degrees of freedom of the Bernal stacked graphene, in a context that can be extended to several mesoscopic scale systems for which the onset from $SU(2)\otimes SU(2)$ Hamiltonians has been assumed.

quant-ph↗

arXiv2024

Deformed AdS/QCD, mesonic mass spectra, and DCE: Still a margin for heavier resonances

The mass spectra of light-flavor mesons are analyzed in a deformed AdS/QCD soft-wall model, driven by four distinct anomalous 5-dimensional mass corrections of the scalar field, coupled to Einstein--Hilbert gravity, from the QCD running coupling. Using the differential configurational entropy (DCE) underlying the families of pseudoscalar, axial-vector, scalar, and vector mesons, the mass spectra of heavier meson resonances with radial quantum numbers beyond the ones already in the summary table of Particle Data Group (PDG) are then estimated. This protocol merges AdS/QCD and experimental data in PDG through Regge-like trajectories. Some of the estimated meson resonances may be identified as further candidates omitted from the summary table in PDG.

hep-ph↗

arXiv2024

Deformations of the AdS-Schwarzschild black brane and the shear viscosity of the quark-gluon plasma

Deformations of the AdS$_5$-Schwarzschild black brane, implemented in the AdS/CFT membrane paradigm, are scrutinized in the dual viscous hydrodynamic infrared limit. The latest experimental data analyses, regarding the shear viscosity-to-entropy density ratio of the quark-gluon plasma produced by heavy-ion collisions at the LHC and RHIC, are shown to constrain these deformations severely. Although corroborating with the robustness of the standard AdS$_5$-Schwarzschild black brane against deformations, there is still a margin for mild deformations which may carry 2-loop quantum corrections to gravity, whose implications to the strongly-coupled dual field theory are addressed and discussed.

hep-th↗

arXiv2024

Generalized extremal branes in AdS/CMT and holographic superconductors

AdS$_4$ generalized extremal branes are scrutinized in the context of AdS/CFT. Holographic superconductors are studied as dual objects to AdS$_4$ generalized black branes, whose coefficients of response and transport in the dual condensed matter theory are calculated and discussed. The holographic Weyl anomaly is also addressed. The holographic superconductor bound current is shown to be enhanced by the parameter controlling the family of AdS$_4$ generalized extremal brane solutions, when compared to the standard AdS$_4$-Reissner-Nordström black brane results. In the probe limit, the electrical DC conductivity for holographic superconductors with AdS$_4$ generalized extremal brane dual background is also reported.

hep-th↗

arXiv2024

Quantum hair and entropy for slowly rotating quantum black holes

We study the quantum hair associated with coherent states describing slowly rotating black holes and show how it can be naturally related with the Bekenstein-Hawking entropy and with 1-loop quantum corrections of the metric for the (effectively) non-rotating case. We also estimate corrections induced by such quantum hair to the temperature of the Hawking radiation through the tunnelling method.

gr-qc↗

arXiv2023

Transport coefficients in AdS/CFT and quantum gravity corrections due to a functional measure

The presence of a functional measure is scrutinized on both sides of the dual gauge/gravity correspondence. Corrections to the transport coefficients in relativistic hydrodynamics are obtained using the linear response procedure. In particular, using first-order hydrodynamics, the shear viscosity, entropy density, diffusion constant, and speed of sound are shown not to acquire any corrections from the functional measure of gravity, for a Minkowski background metric. On the other hand, the energy density, the pressure, the relaxation time, the bulk viscosity, the decay rate of sound waves, and coefficients of conformal traceless tensor fields, are shown to carry significant quantum corrections due to the functional measure, even for a flat background. They all acquire an imaginary part that reflects the instability of the strongly-coupled fluids on the boundary CFT. This opens up the possibility of testing quantum gravity with the quark-gluon plasma.

hep-th↗

arXiv2023

Information entropy of nuclear electromagnetic transitions in AdS/QCD

Electromagnetic transitions involving nucleons and their resonances are here presented in the fermionic sector of the AdS/QCD soft-wall model, using the differential configurational entropy (DCE) as a measure of information entropy. The DCE is employed to derive adjustable parameters that define the minimal and nonminimal couplings in the nuclear interaction with a gauge vector field, in the nucleonic $γN \to N^*(1535)$ transition. The values obtained comply with phenomenological data with good accuracy.

hep-th↗

arXiv2023

Configurational entropy and shape complexity of strange vector kaons in AdS/QCD

The mass spectrum of strange vector kaons resonances is scrutinized, using AdS/QCD with a deformed dilaton that arises from the constituent quark masses. Both the differential configurational entropy and the differential configurational complexity are computed and used to achieve the mass spectrum of strange vector kaons resonances with higher radial quantum numbers. This approach amalgamates AdS/QCD and the experimental mass spectrum of already detected strange vector kaons in the Particle Data Group, providing a hybrid technique to study the next generation of strange vector kaons resonances.

hep-ph↗

arXiv2022

Gravitational decoupling, hairy black holes and conformal anomalies

Hairy black holes in the gravitational decoupling setup are studied from the perspective of conformal anomalies. Fluctuations of decoupled sources can be computed by measuring the way the trace anomaly-to-holographic Weyl anomaly ratio differs from unit. Therefore the gravitational decoupling parameter governing three hairy black hole metrics is then bounded to a range wherein one can reliably emulate AdS/CFT with gravitational decoupled solutions, in the tensor vacuum regime.

hep-th↗

arXiv2022

Gravitational decoupling of generalized Horndeski hybrid stars

Gravitational decoupled compact polytropic hybrid stars are here addressed in generalized Horndeski scalar-tensor gravity. Additional physical properties of hybrid stars are scrutinized and discussed in the gravitational decoupling setup. The asymptotic value of the mass function, the compactness, and the effective radius of gravitational decoupled hybrid stars are studied for both cases of a bosonic and a fermionic prevalent core. These quantities are presented and discussed as functions of Horndeski parameters, the decoupling parameter, the adiabatic index, and the polytropic constant. Important corrections to general relativity and generalized Horndeski scalar-tensor gravity, induced by the gravitational decoupling, comply with available observational data. Particular cases involving white dwarfs, boson stellar configurations, neutron stars, and Einstein-Klein-Gordon solutions, formulated in the gravitational decoupling context, are also scrutinized.

gr-qc↗

arXiv2022

Holographic entanglement entropy, deformed black branes, and deconfinement in AdS/QCD

A family of deformed black branes is employed to examine the confinement/deconfinement phase transition in AdS/QCD. The holographic entanglement entropy (HEE) plays the role of the order parameter driving the confinement/deconfinement phase transition. The binding energy of quark-antiquark bound states and the critical length that makes a null variation of the HEE, together with the critical temperature separating the deconfined quark-gluon plasma to the confined hadronic phase, are discussed in the deformed black brane background, matching current experimental hadronic data.

hep-th↗

arXiv2021

AdS graviton stars and differential configurational entropy

AdS graviton stars are studied in the differential configurational entropy setup, as solutions of the effective Einstein field equations that backreact to compactification. With the critical central density of AdS graviton stars, the differential configurational entropy is derived and computed, presenting global minima for a wide range of stellar mass magnitude orders. It indicates insular domains of configurational stability for AdS graviton stars near astrophysical neutron star densities. Other relevant features are also reported.

gr-qc↗

arXiv2021

Gravitational decoupling and superfluid stars

The gravitational decoupling is applied to studying minimal geometric deformed (MGD) compact superfluid stars, in covariant logarithmic scalar gravity on fluid branes. The brane finite tension is shown to provide more realistic values for the asymptotic value of the mass function of MGD superfluid stars, besides constraining the range of the self-interacting scalar field, minimally coupled to gravity. Several other physical features of MGD superfluid stars, regulated by the finite brane tension and a decoupling parameter, are derived and discussed, with important corrections to the general-relativistic limit that corroborate to current observational data.

gr-qc↗