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R. Menezes

Publications and source records attributed to R. Menezes.

At least 37 records · Page 2Linked to original sources
arXiv2024

Geometrically constrained multifield models with BNRT solutions

In this paper, we investigate multifield models in which the two-field BNRT model is coupled to a third field through mediator functions in the Lagrangian density. To conduct the investigation, we obtain the equations of motion and develop a first-order formalism based on energy minimization. Two possibilities are considered: i) the third field acting in the mediator functions to modify the BNRT solutions; ii) the BNRT fields feeding the mediator function to produce effects in the kink solution of the third field. In the case i), the results show that the solutions may be related to the standard ones with the coordinate redefined in terms of the mediator functions if they are equal. This allows to induce effects similar to geometric constrictions in the core, or to compactify the tail of the BNRT solutions. If the mediator functions differ one from another, we show that the effects are distinct, with the compactification of just one of the two-field solutions. In the case ii), the orbit parameter of the model plays an important role, modifying the mediator function that induces changes in the profile of the kink associated to the third field.

hep-th↗
arXiv2024

Geometrically Constrained Localized Configurations: First-Order Framework and Analytical Solutions

This work deals with the presence of topological structures in models of two real scalar fields in the two-dimensional spacetime. The subject concerns the presence of a geometric constriction, which appears with a modification of the kinetic term of one of the two fields. We elaborate on the construction of a first-order framework, which directly contributes to find analytical solutions. We describe several distinct possibilities, in particular, the case where the first-order equations do not separate. This is much harder, but we use the integrating factor to deal with analytical configurations. The proposed methodology help us deal with localized structures of both the Néel and Bloch type very naturally, and we end the work suggesting some possibilities of applications in distinct areas of nonlinear science.

hep-th↗
arXiv2023

Flat and bent branes in Born-Infeld-like scalar field models

In this work, we investigate the presence of thick branes modeled by a single scalar field with Born-Infeld-like dynamics. We consider the 4-dimensional metric being Minkowski, de Sitter or anti-de Sitter. We obtain the field equations and the conditions to get a first order formalism compatible with them. To illustrate our procedure, some specific models are presented. They support localized warp factor and have their properties controlled by the 4-dimensional cosmological constant. In particular, a hybrid brane may arise, with a thick or thin profile depending on the extra dimension being inside or outside a compact space.

hep-th↗
arXiv2023

Maxwell-scalar system and scalar field with impurity: novel approach to find nontrivial solutions

In this work, we investigate a Maxwell-scalar model that couples the scalar and gauge fields through the electric permittivity and another model, in which the scalar field lives in the presence of impurity. By considering a single spatial dimension, we determine the conditions under which the model with impurity can be seen as an effective model for the Maxwell-scalar system, having similar solutions. This correspondence shows that the impurity can be used to describe the presence of a charge density, and we use it to verify that the impurity-free case, which supports minimum energy configurations, is related to the case of point charges. We also investigate a class of impurities which modifies the core of the scalar field, and find the corresponding nontrivial charge densities and electric fields. In particular, the asymptotic behavior in terms of the impurity is also studied, leading to solutions exhibiting long-range or quasi-compact profile.

hep-th↗
arXiv2023

Geometrically constrained kinklike configurations engendering long range, double exponential, half-compact and compact behavior

We describe a procedure that contributes to modify the asymptotic behavior of kinks in a model described by two real scalar fields. The investigation takes advantage of a first order formalism based on energy minimization to unveil how to modify the asymptotic profile of kinklike configurations. In particular, we show that the exponential tails of standard kinklike configurations can be smoothly modified to engender long range, double exponential, half-compact or compact behavior.

hep-th↗
arXiv2023

Kinks in cuscuton-like models with two scalar fields

This work deals with the presence of localized structures in relativistic systems described by two real scalar fields in two-dimensional spacetime. We consider the usual two-field model with the inclusion of the cuscuton term, which couples the fields regardless the potential. First we follow the steps of previous work to show that the system supports a first-order framework, allowing us to obtain the energy of solutions without knowing their explicit form. The cuscuton term brings versatility into the first-order equations, which gives rise to interesting modifications in the profiles of topological configurations, such as the smooth control over their slope and the internal structure of the energy density.

hep-th↗
arXiv2023

Vortices in Maxwell-Higgs models with a global factor

This paper deals with planar vortices in a generalized model that presents a global factor which depends on the scalar field in the Nielsen-Olesen Lagrange density. We show that the system supports a first order framework. Contrary to what occurs with kinks in the line, planar vortices require the presence of constraints that brings modifications into the first order equations. Novel features are unveiled, such as finite energy configurations with infinite energy density at the origin and the presence of parameters that modifies the energy, keeping the solutions unchanged.

hep-th↗
arXiv2023

Cuscuta-Galileon Braneworlds

We investigate braneworlds modeled by topological solutions that arise from the so-called Cuscuta-Galileon model. We develop a first order framework and illustrate our procedure with the scalar field having the well-known hyperbolic tangent profile. We find conditions that must be imposed to the parameters of the model in order to have solutions connecting minima of the potential, with the brane constrained to interpolate Minkowski and anti de Sitter geometries. We also find solutions where the brane only interpolates anti de Sitter geometry. In both cases, the gravity sector of the brane is stable against small fluctuations of the metric.

hep-th↗
arXiv2022

Generalized Jackiw-Teitelboim gravity in presence of Bloch brane-like models

We investigate generalized Jackiw-Teitelboim gravity, coupling the dilaton field with two scalar matter fields. We obtain the equations of motion of the fields and investigate the linear perturbation of the solutions in general. We study two specific situations that allow analytic solutions with topological behavior and check how the dilaton field, the warp factor and Ricci scalar behave. In particular, we have shown how the parameters can be used to modify the structure of the solutions. Moreover, the perturbations are in general described by intricate coupled differential equations, but in some specific cases we could construct the corresponding zero modes analytically.

hep-th↗
arXiv2021

Maxwell-scalar device based on the electric dipole

In this work we study the electric field of a dipole immersed in a medium with permittivity controlled by a real scalar field which is non-minimally coupled to the Maxwell field. We model the system with an interesting function, which allows the presence of exact solutions, describing the possibility of the permittivity to encapsulate the charges at very high values, giving rise to an effect that is not present in the standard situation. The results are of direct interest to applications for emission and absorption of radiation, and may motivate new studies concerning binary stars and black holes in gravity scenarios of current interest.

hep-th↗
arXiv2020

Electrically charged localized structures

This work deals with an Abelian gauge field in the presence of an electric charge immersed in a medium controlled by neutral scalar fields, which interact with the gauge field through a generalized dielectric function. We develop an interesting procedure to solve the equations of motion, which is based on the minimization of the energy, leading us to a first order framework where minimum energy solutions of first order differential equations solve the equations of motion. We investigate two distinct models in two and three spatial dimensions and illustrate the general results with some examples of current interest, implementing a simple way to solve the problem with analytical solutions that engender internal structure.

physics.gen-ph↗
arXiv2020

New twinlike models for scalar fields

This work investigates twinlike scalar field models that support kinks with the same energy density and stability. We find the first order equations compatible with the equations of motion. We use them to calculate the conditions under which they attain the twinlike character. The linear stability is also investigated, and there we show that the addition of extra requirements may lead to the same stability under small fluctuations.

hep-th↗
arXiv2020

Long range vortex configurations in generalized models with the Maxwell or Chern-Simons dynamics

In this work we deal with vortices in Maxwell-Higgs or Chern-Simons-Higgs models that engender long range tails. We find first order differential equations that support minimum energy solutions which solve the equations of motion. In the Maxwell scenario, we work with generalised magnetic permeabilities that lead to vortices described by solutions, magnetic field and energy density with power-law tails that extend farther than the standard exponential ones. We also find a manner to obtain a Chern-Simons model with the same scalar and magnetic field profiles of the Maxwell case. By doing so, we also find vortices with the aforementioned long range feature, which is also present in the electric field in the Chern-Simons model. The present results may motivate investigations on nonrelativistic models, in particular in the case involving Rydberg atoms, which are known to present long range interactions and relatively long lifetimes.

hep-th↗
arXiv2020

Vortices in Maxwell-Chern-Simons-Higgs models with nonminimal coupling

We investigate the presence of vortex configurations in generalized Maxwell-Chern-Simons models with nonminimal coupling, in which we introduce a function that modifies the dynamical term of the scalar field in the Lagrangian. We first follow a route already considered in previous works to develop the Bogomol'nyi procedure, and, in this context, we use the first order equations to obtain a vortex with a novel behavior at its core. We then go further and introduce a novel procedure to develop the Bogomol'nyi methodology. It supports distinct first order equations, and we then investigate another model, in which the vortex may engender inversion of the magnetic flux, an effect with no precedents in the study of vortices within the nonminimal context.

hep-th↗
arXiv2020

Quasi-compact vortices

We deal with planar vortex structures in Maxwell-Higgs models in the presence of a generalized magnetic permeability. The model under investigation engenders a real parameter that controls the behavior of the tail of the solutions and of the quantities associated to them. As the parameter gets larger, the solutions attain their boundary values faster, unveiling the existence of a peculiar feature, the presence of double exponential tails. However, the solutions are not compact so we call them quasi-compact vortices.

hep-th↗
arXiv2020

Full-sky searches for anisotropies in UHECR arrival directions with the Pierre Auger Observatory and the Telescope Array

The arrival directions of ultra-high-energy cosmic rays appear to be approximately isotropically distributed over the whole sky, but the last-generation UHECR detector arrays, the Pierre Auger Observatory (Auger) and the Telescope Array (TA), have detected thousands of events, allowing us to study small deviations from isotropy. So far, Auger has detected a large-scale anisotropy consistent with a $\sim 6.5\%$ dipole moment in the distribution of cosmic rays with $E > 8$~EeV, and both collaborations have reported indications for smaller-scale anisotropies at higher energies. On the other hand, neither array has full-sky coverage, the Auger field of view being limited to declinations $δ< +45^\circ$ and the TA one to $δ> -16^\circ$. Searches for anisotropies with full-sky coverage thus require combining data from both arrays. A working group with members from both collaborations has been established for this task. Since even a minor systematic error in the energy determinations at either of the arrays could result in a sizeable spurious anisotropy along the north--south axis, we devised a method to cross-calibrate the energy scales of the two experiments with respect to each other by using events in a declination band within the intersection of their fields of view. In this contribution, we report on both updates on blind searches for anisotropies and the first full-sky studies of flux models based on possible local extragalactic sources.

astro-ph.HE↗
arXiv2019

Stability of kinklike structures in generalized models

We study the stability of topological structures in generalized models with a single real scalar field. We show that it is driven by a Sturm-Liouville equation and investigate the conditions that lead to the existence of explicit supersymmetric operators that factorize the stability equation and allow us to construct partner potentials. In this context, we discuss the property of shape invariance as a possible manner to calculate the discrete states and their respective eigenvalues.

hep-th↗