arXiv subjects

Vitorio A. De Lorenci

Publications and source records attributed to Vitorio A. De Lorenci.

17 recordsLinked to original sources

arXiv2026

Gravitational Effects on Light Propagation in Linear Magnetoelectrics and Plasmas

A covariant formalism for electromagnetism is used to investigate the effects of light propagation within certain material systems under the influence of a background gravitational field. Specifically, dielectric media described by linear constitutive relations, as well as magnetized plasma media, such as the magnetosphere of neutron stars, are examined. Estimates for detecting gravitational effects through precise refractive index measurements within these scenarios are provided.

physics.gen-ph↗

arXiv2025

Effective spacetime description of light propagation in linear magnetoelectric media

Formal analogies between gravitational and optical phenomena have been explored for over a century, providing valuable insights into kinematic aspects of general relativity. Here, this analogy is employed to study light propagation in linear magnetoelectric media from an effective spacetime perspective. Starting from Maxwell's equations in covariant form, it is shown that an effective metric can always be identified for linear, non-dispersive magnetoelectric materials. The effective metric is then used to construct analog models in the limit of geometric optics. Among the optical effects analyzed, it is shown that under reasonable assumptions on the magnitude of the magnetoelectric response, a one-way propagation region can be established, which behaves analogously to an event horizon.

gr-qc↗

arXiv2025

Gravitational wave signals from primordial black holes orbiting solar-type stars

Primordial black holes (PBHs) with masses between $10^{14}$ and $10^{20}$ kg are candidates to contribute a substantial fraction of the total dark matter abundance. When in orbit around the center of a star, which can possibly be a completely interior orbit, such objects would emit gravitational waves, as predicted by general relativity. In this work, we examine the gravitational wave signals emitted by such objects when they orbit typical stars, such as the Sun. We show that the magnitude of the waves that could eventually be detected on Earth from a possible PBH orbiting the Sun or a neighboring Sun-like star within our galaxy can be significantly stronger than those originating from a PBH orbiting a denser but more distant neutron star (NS). Such signals may be detectable by the LISA gravitational-wave detector. In addition, we estimate the contribution that a large collection of such PBH-star systems would make to the stochastic gravitational-wave background (SGWB) within a range of frequencies to which pulsar timing arrays are sensitive.

gr-qc↗

arXiv2025

Light propagation in magnetoelectric materials: The role of optical coefficients in refractive index modulation

Investigations into optical phenomena associated with nonlinear magnetoelectric effects are attracting growing attention within the scientific community. Technologies constantly demand new materials capable of exhibiting precise and controllable responses to external electromagnetic fields. In this context, the optics of such materials is of remarkable importance. Here, working in a lossless and non-dispersive regime, electromagnetic wave propagation in materials presenting linear and nonlinear optical coefficients is investigated. We expand the discussion of the roles of nonlinear coefficients by examining special cases in which the contribution of the magnetoelectric optical coefficients $α_{ij}$, $β_{ijk}$, and $γ_{ijk}$ to birefringence and nonreciprocal phenomena is elucidated. Notably, expressions that directly connect the magnetoelectric coefficients to the refractive indices of the medium are fully derived. These expressions enable the direct measurement of all components of each nonlinear magnetoelectric coefficient, providing an advancement over previous works. This development bridges theoretical models with experimental applications, offering possibilities for the optical characterization of magnetoelectric effects.

physics.optics↗

arXiv2025

Analytical solutions for the quantum Brownian motion of a particle during a quantum quench

A particle subjected to a fluctuating force originated from its interaction with an external quantum system undergoes quantum Brownian motion. This phenomenon is investigated in detail for the case of a particle confined by a harmonic potential and allowed to interact with a reservoir modeled as a continuum of oscillators, with particular emphasis on transient effects. Assuming a linear coupling between the particle and the reservoir, canonical quantization of the system is implemented, and analytical expressions for the quantum correlations are derived. These correlations are then applied to analyze energy conservation, and the particle Brownian motion is characterized from the perspective of the energy extracted from the reservoir.

quant-ph↗

arXiv2024

Macroscopic quantum superpositions in superconducting circuits

A possible route to test whether macroscopic systems can acquire quantum features using superconducting circuits is here presented. It is shown that under general assumptions a classical test current pulse of fixed energy and adjustable length acquires quantum features after interacting with the quantum vacuum of the photon field. Further, it is shown that the mere existence of vacuum fluctuations can lead to the breakdown of energy and momentum conservation, and as the length of the pulse grows with respect to the characteristic size of the quantum system, the test pulse undergoes quantum-to-classical transition. This model differs from previous ones for its simplicity and points towards a new way of creating correlated systems suitable for quantum-based technology.

quant-ph↗

arXiv2024

Orbital motion of primordial black holes crossing Solar-type stars

Primordial black holes (PBHs) are hypothetical objects that could have originated from density fluctuations in a very early phase of our Universe. Recent observations restrict the masses that such PBHs could have, if they are to constitute all of dark matter today: $10^{17} \, {\rm g} \leq m \leq 10^{23} \, {\rm g}$. With such low masses, general relativity predicts that the corresponding radii for the PBHs would be atomic or subatomic in size. When captured by a star, such a tiny PBH could exhibit an orbit completely or partially inside the body of the star, without significantly changing its mass for quite a long time. Here we examine the possible trajectories of a PBH that is captured by a Sun-like star. When in motion in the interior of the star, the amount of stellar mass that effectively interacts with the PBH will be a function of its distance to the center of the star. As a consequence, a strong effect on the shape of the orbits emerges, leading to PBH trajectories that could be open or closed, and exhibiting a rich variety of patterns.

astro-ph.CO↗

arXiv2022

Aspects of wave propagation in a nonlinear medium: birefringence and the second-order magnetoelectric coefficients

Magnetoelectric materials have the interesting property of exhibiting polarization induced by a magnetic field or magnetization induced by an electric field. As a consequence, a multitude of effects can be produced by means of controllable external fields. A method for deriving phase velocities and its corresponding polarization vectors for light rays in nonlinear optical materials in a nondispersive regime is here revisited and used to study wave propagation in a certain class of second-order magnetoelectric media. In particular, the birefringence effect is theoretically examined and it is shown that it can be used as a tool to obtain most of the second-order magnetoelectric coefficients $β_{ijk}$ of a material having an isotropic linear sector. Estimates of the effect are presented. Some optical properties of nonlinear materials presenting a natural optic axis are also discussed.

physics.optics↗

arXiv2017

Controlled opacity in a class of nonlinear dielectric media

Motivated by new technologies for designing and tailoring metamaterials, we seek properties for certain classes of nonlinear optical materials that allow room for a reversibly controlled opacity-to-transparency phase transition through the application of external electromagnetic fields. We examine some mathematically simple models for the dielectric parameters of the medium and compute the relevant geometric quantities that describe the speed and polarization of light rays.

physics.optics↗

arXiv2015

Multirefringence phenomena in nonlinear electrodynamics

Wave propagation in nonlinear theories of the electromagnetism described by Lagrangian densities dependent upon its two local invariants L(F, G) is revisited. On the light of the recent findings in metamaterials, it is here shown that trirefringence is also a possible phenomenon to occur in the realm of such nonlinear theories. A specific model exhibiting this effect is investigated both in terms of phase and group velocities. It is claimed that wave propagation in some well known nonlinear models for spin-one fields, like QED and QCD in certain regimes, may exhibit trirefringence.

physics.optics↗

arXiv2014

One-way propagation of light in Born-Infeld-like metamaterials

We propose and investigate a family of nonlinear metamaterials in which light rays propagate just in one direction -- one-way propagation. Furthermore, we argue how such nonlinear media could provide an analog model for investigating the Born-Infeld Lagrangian in the realm of fields larger than its scale field.

physics.optics↗

arXiv2012

Trirefringence in nonlinear metamaterials

We study the propagation of electromagnetic waves in the limit of geometrical optics for a class of nearly transparent nonlinear uniaxial metamaterials for which their permittivity tensors present a negative principal component. Their permeability are assumed positive and dependent on the electric field. We show that light waves experience triple refraction -- trirefringence. Additionally to the ordinary wave, two extraordinary waves propagate in such media.

physics.optics↗

arXiv2010

Nonsingular and accelerated expanding universe from effective Yang-Mills theory

The energy-momentum tensor coming from one-parameter effective Yang- Mills theory is here used to describe the matter-energy content of the homogeneous and isotropic Friedmann cosmology in its early stages. The behavior of all solutions is examined. Particularly, it is shown that only solutions corresponding to an open model allow the universe to evolve into an accelerated expansion. This result appears as a possible mechanism for an inflationary phase produced by a vector field. Further, depending on the value of some parameters characterizing the system, the resulting models are classified as singular or nonsingular.

gr-qc↗

arXiv2009

Semiclassical backreaction around a nearly spinning cosmic string

This paper investigates semiclassical backreaction of a conformally coupled massless scalar field on the geometrical background of a nearly spinning cosmic string - the spin density is smaller than, but arbitrarily close to, the dislocation parameter. As the spin density approaches the dislocation parameter, it is shown that an "ergoregion" spreads indefinitely around the cosmic string, boosting along the string axis the once static observers. Considering that the geometrical background contains closed timelike curves when the spin density exceeds the dislocation parameter, it is argued that the appearance of the "ergoregion" may be part of a chronology protection mechanism that takes place in related non stationary geometries.

gr-qc↗

arXiv2008

Magnetoelectric birefringence revisited

Electromagnetic wave propagation inside isotropic material media characterized by dielectric coefficients $\varepsilon_{μν}(E,B)$ and $μ_{μν}(E,B)$ is examined. The regime of the eikonal approximation is considered. The Hadamard method of field disturbances is used and the dispersion relations are obtained by solving the Fresnel equation. Some applications of the formalism are presented. Particularly, birefringence phenomena induced by applied external fields are derived and discussed. It is shown that magnetoelectric birefringence effect can occur even without the presence of Kerr and Cotton-Mouton effects, provided the physical system satisfies certain conditions.

physics.optics↗

arXiv2004

Spinning strings, cosmic dislocations and chronology protection

A massless scalar field is quantized in the background of a spinning string with cosmic dislocation. By increasing the spin density toward the dislocation parameter, a region containing closed timelike curves (CTCs) eventually forms around the defect. Correspondingly, the propagator tends to the ordinary cosmic string propagator, leading therefore to a mean-square field fluctuation, which remains well behaved throughout the process, unlike the vacuum expectation value of the energy-momentum tensor, which diverges due to a subtle mechanism. These results suggest that back reaction leads to the formation of a "horizon" that protects from the appearance of CTCs.

gr-qc↗

arXiv1997

Topology Change in Canonical Quantum Cosmology

We develop the canonical quantization of a midisuperspace model which contains, as a subspace, a minisuperspace constituted of a Friedman-Lema\^ıtre-Robertson-Walker Universe filled with homogeneous scalar and dust fields, where the sign of the intrinsic curvature of the spacelike hypersurfaces of homogeneity is not specified, allowing the study of topology change in these hypersurfaces. We solve the Wheeler-DeWitt equation of the midisuperspace model restricted to this minisuperspace subspace in the semi-classical approximation. Adopting the conditional probability interpretation, we find that some of the solutions present change of topology of the homogeneous hypersurfaces. However, this result depends crucially on the interpretation we adopt: using the usual probabilistic interpretation, we find selection rules which forbid some of these topology changes.

gr-qc↗