arXiv subjects

Gustavo de Oliveira

Publications and source records attributed to Gustavo de Oliveira.

10 recordsLinked to original sources

arXiv2026

Bjorken Flow of Holographic R-Charged Plasmas

We numerically investigate the time evolution of several physical observables for the so-called 2 R-Charge Black Hole (2RCBH) model undergoing Bjorken flow. The 2RCBH model corresponds to a top-down holographic construction describing a strongly interacting conformal fluid defined at finite temperature and R-charge density. Taken together with previous findings for the purely thermal $\mathcal{N}=4$ Supersymmetric Yang-Mills (SYM) plasma, and the 1 R-Charge Black Hole (1RCBH) model, our results for the 2RCBH model provide strong numerical evidence for the existence of far-from-equilibrium correlations between the non-equilibrium holographic entropy defined through the area of the apparent horizon of dynamical bulk black holes, and the expectation value of the energy-momentum tensor of the dual boundary quantum field theory. Such correlations are relevant in the pre-hydrodynamic stages of some initial data evolved in time, and seem to hold at least for strongly interacting conformal fluids, be they charged or neutral.

hep-th↗

arXiv2026

Homogeneous isotropization dynamics and entropy production in a hot and dense strongly interacting fluid

We numerically investigate the time evolution of the non-equilibrium entropy during the homogeneous isotropization dynamics of the 2 R-Charge Black Hole (2RCBH) model, corresponding to a top-down holographic fluid defined at finite temperature and R-charge density. In addition to the entropy production, we also analyze the time evolution of the pressure anisotropy and the scalar condensate of the medium. When the system is far-from-equilibrium the dominant and weak energy conditions can be transiently violated. For all initial conditions considered, we observe the emergence of a periodic sequence of several close plateaus forming a stairway for the entropy as the system approaches thermodynamic equilibrium. The entropy stairway allows for the entropy to encode a periodic structure without violating the second law of thermodynamics. In fact, the complex frequency of the lowest quasinormal mode (QNM) of the system is directly tied to the periodic structure of the entropy stairway, which provides another explicit numerical confirmation of a quite general connection between entropy production and QNMs previously discovered in the literature. Furthermore, when the chemical potential of the 2RCBH fluid exceeds a certain threshold, the pressure anisotropy exhibits a late-time decay governed by a purely imaginary QNM, and as the system is doped with increasing values of R-charge chemical potential the late-time equilibration pattern of the pressure anisotropy gets increasingly deformed, eventually losing the oscillatory behavior observed at lower values of chemical potential.

hep-th↗

arXiv2026

Dynamical Casimir effect under the action of gravitational waves

Several nontrivial phenomena emerge when a quantum field is subjected to dynamical perturbations, with prominent examples including the Hawking and Unruh effects, as well as the dynamical Casimir effect. In this work, we compute the number of particles produced via the dynamical Casimir effect in an ideal cavity, where one of the mirrors is allowed to move under the influence of a gravitational wave. Assuming an oscillatory mirror motion and a plane gravitational wave, we identify the resonance conditions that lead to an exponential increase in the number of created particles through parametric amplification.

quant-ph↗

arXiv2025

Mutual information and holographic entanglement entropy for strongly-coupled R-charged plasmas

We numerically evaluate, for slab entangling geometries, the mutual information and the holographic entanglement entropy between strongly interacting fields in different spatial regions for two different conformal holographic models at finite temperature and R-charge density. The 1 R-Charge Black Hole (1RCBH) model describes a strongly interacting fluid with a critical point in its phase diagram, while the 2 R-Charge Black Hole (2RCBH) model has no critical point. In both models, we find that the mutual information tends to be overall reduced by increasing the value of $μ/T$ at larger values of the separation length $x$ between two disjoint spatial regions of the medium, while the opposite tendency is observed at lower values of $x$. We also observe that very close to the critical point of the 1RCBH model, the mutual information tends to increase with increasing $μ/T$ in the stable branch of black hole solutions. Moreover, the mutual information between the fields in the two disjoint regions is observed to be enhanced by increasing the characteristic size $\ell$ of these regions, with such an enhancement asymptotically saturating, thus suggesting the existence of a finite field correlation length between the disjoint regions of the system. The finite part of the entanglement entropy may change sign depending on the values of $μ/T$ and $\ell$, and it correctly detects the critical point of the 1RCBH model, a feature that is also adequately detected by the mutual information.

hep-th↗

arXiv2024

New purely damped pairs of quasinormal modes in a hot and dense strongly-coupled plasma

Perturbed black holes exhibit damped oscillations whose eigenfrequencies define their quasinormal modes (QNMs). In the case of asymptotically Anti-de Sitter (AdS) black holes, the spectra of QNMs are related to the near-equilibrium behavior of specific strongly interacting quantum field theories via the holographic gauge-gravity duality. In the present work, we numerically obtain the spectra of homogeneous non-hydrodynamic QNMs of a top-down holographic construction called the 2 R-Charge Black Hole (2RCBH) model, which describes a hot and dense strongly-coupled plasma. The main result is the discovery of a new structure of pairs of purely imaginary QNMs. Those new purely damped QNMs dominate the late time equilibration of the strongly-coupled plasma at large values of the chemical potential, while at lower values the fundamental QNMs are instead ordinary poles with imaginary and real parts describing oscillatory decaying perturbations. We also observe a new phenomenon of asymptotic pole fusion for different pairs of purely imaginary QNMs at asymptotically large values of the chemical potential. This phenomenon corresponds to the asymptotic merging of the two poles within each pair of purely imaginary QNMs, with the different pairs of merged poles being evenly spaced by a constant value of $4π$ in all the different perturbation channels associated to different irreducible representations of the spatial $SO(3)$ rotation symmetry of the medium. In particular, this indicates that characteristic equilibration times for the plasma develop upper bounds that cannot be surpassed by further doping the medium with increasing values of the chemical potential.

hep-th↗

arXiv2023

Thermodynamic entropy production in the dynamical Casimir effect

This paper address the question of thermodynamic entropy production in the context of the dynamical Casimir effect. Specifically, we study a scalar quantum field confined within a one-dimensional ideal cavity subject to time-varying boundary conditions dictated by an externally prescribed trajectory of one of the cavity mirrors. The central question is how the thermodynamic entropy of the field evolves over time. Utilizing an effective Hamiltonian approach, we compute the entropy production and reveal that it exhibits scaling behavior concerning the number of particles created in the short-time limit. Furthermore, this approach elucidates the direct connection between this entropy and the emergence of quantum coherence within the mode basis of the field. In addition, by considering a distinct approach based on the time evolution of Gaussian states we examine the long-time limit of entropy production within a single mode of the field. This approach results in establishing a connection between the thermodynamic entropy production in a single field mode and the entanglement between that particular mode and all other modes. Consequently, by employing two distinct approaches, we comprehensively address both the short-term and long-term dynamics of the system. Our results thus link the irreversible dynamics of the field, as measured by entropy production and induced by the dynamical Casimir effect, to two fundamental aspects of quantum mechanics: coherence and entanglement.

quant-ph↗

arXiv2019

Mean-field dynamics for mixture condensates via Fock space methods

We consider a mean-field model to describe the dynamics of $N_1$ bosons of species one and $N_2$ bosons of species two in the limit as $N_1$ and $N_2$ go to infinity. We embed this model into Fock space and use it to describe the time evolution of coherent states which represent two-component condensates. Following this approach, we obtain a microscopic quantum description for the dynamics of such systems, determined by the Schrödinger equation. Associated to the solution to the Schrödinger equation, we have a reduced density operator for one particle in the first component of the condensate and one particle in the second component. In this paper, we estimate the difference between this operator and the projection onto the tensor product of two functions that are solutions of a system of equations of Hartree type. Our results show that this difference goes to zero as $N_1$ and $N_2$ go to infinity. Our hypotheses allow the Coulomb interaction.

math-ph↗

arXiv2014

Quantum dynamics of a particle constrained to lie on a surface

We consider the quantum dynamics of a charged particle in Euclidean space subjected to electric and magnetic fields under the presence of a potential that forces the particle to stay close to a compact surface. We prove that, as the strength of this constraining potential tends to infinity, the motion of this particle converges to a motion generated by a Hamiltonian over the surface superimposed by an oscillatory motion in the normal directions. Our result extend previous results by allowing magnetic potentials and more general constraining potentials.

math-ph↗

arXiv2012

Quantitative Derivation of the Gross-Pitaevskii Equation

Starting from first principle many-body quantum dynamics, we show that the dynamics of Bose-Einstein condensates can be approximated by the time-dependent nonlinear Gross-Pitaevskii equation, giving a bound on the rate of the convergence. Initial data are constructed on the bosonic Fock space applying an appropriate Bogoliubov transformation on a coherent state with expected number of particles N. The Bogoliubov transformation plays a crucial role; it produces the correct microscopic correlations among the particles. Our analysis shows that, on the level of the one particle reduced density, the form of the initial data is preserved by the many-body evolution, up to a small error which vanishes as N^{-1/2} in the limit of large N.

math-ph↗

arXiv2010

Asymptotics for Fermi curves: small magnetic potential

We consider complex Fermi curves of electric and magnetic periodic fields. These are analytic curves in C^2 that arise from the study of the eigenvalue problem for periodic Schroedinger operators. We characterize a certain class of these curves in the region of C^2 where at least one of the coordinates has "large" imaginary part. The new results in this work extend previous results in the absence of magnetic field to the case of "small" magnetic field. Our theorems can be used to show that generically these Fermi curves belong to a class of Riemann surfaces of infinite genus.

math-ph↗