arXiv subjects

D. M. Dantas

Publications and source records attributed to D. M. Dantas.

15 recordsLinked to original sources

arXiv2021

Quasinormal frequencies for a black hole in a bumblebee gravity

After recent observational events like the LIGO-Virgo detections of gravitational waves and the shadow image of M87* supermassive black hole by Event Horizon Telescope (EHT), the theoretical study of black holes was significantly improved. Quantities as quasinormal frequencies, shadows, and light deflection become more important to analyze black hole models. In this context, an interesting scenario to study is a black hole in the bumblebee gravity. The bumblebee vector field imposes a spontaneous symmetry breaking that allows the field to acquire a vacuum expectation value that generates Lorentz-Violating (LV) into the black hole. In order to compute the quasinormal modes (QNMs) via the WKB method, we obtain the Reege-Wheeler's equation with a bell-shaped potential for this black hole. Both QNMs, the scalar and tensorial modes, are computed for the black hole in the bumblebee scenario. Moreover, the stability of the Schwarzschild-like solution and some bounds to LV parameters are analyzed.

gr-qc↗

arXiv2020

The Casimir effect for the scalar and Elko fields in a Lifshitz-like field theory

In this work, we obtain the Casimir energy for the real scalar field and the Elko neutral spinor field in a field theory at a Lifshitz fixed point (LP). We analyze the massless and the massive case for both fields using dimensional regularization. We obtain the Casimir energy in terms of the dimensional parameter and the LP parameter. Particularizing our result, we can recover the usual results without LP parameter in (3+1) dimensions presented in the literature. Moreover, we compute the effects of the LP parameter in the thermal corrections for the massless scalar field.

hep-th↗

arXiv2019

Configurational entropy and Newton's Law in double sine-Gordon braneworlds

In this work, we evaluate the Shannon-like entropic measure of spatially-localized functions for a five-dimensional braneworld generated by a double sine-Gordon (DSG) potential. The differential configurational entropy (DCE) has been shown in several recent works to be a configurational informational measure (CIM) that selects critical points and brings out phase transitions in confined energy models with arbitrary parameters. We select the DSG scenario because it presents an energy-degenerate spatially localized profile where the solutions to the scalar field demonstrate critical behavior that is only a result of geometrical effects. As we will show, the DCE evaluation provides a method for predicting the existence of a transition between the phases of the domain wall solutions. Moreover, the entropic measure reveals information about the model that is capable of describing the phase sector where we obtain resonance modes on the massive spectra of the graviton. The graviton resonance lifetimes are related to the existence of scales on which 4D gravity is recovered. Thus, we correlate the critical points defined by the {CIMs} with the existence of resonances and their lifetimes. To extend our research regarding this system, we calculate the corrections to Newton's Law coming from the graviton modes.

gr-qc↗

arXiv2019

New class of solutions of a generalized $O(3)$-sigma Chern-Simons model

In this work, we investigated the existence of compacton-like configuration in the O(3)-sigma model. We consider a minimally coupled O(3)-sigma model with a gauge field governed by a generalized Chern-Simons term. Contrary to that established in the literature, we impose a new set of boundary conditions and, we find solutions of the variable fields and the respective energy density in the Bogomol'nyi limit. On the other hand, the introduction of a parameter $ω$ in the Chern-Simons term can be adjusted to leads to finite-energy solutions of the model. Moreover, compact-like structures were studied with the evolution of this $ω$ generalized Chern-Simons term.

hep-th↗

arXiv2018

Quasi-normal modes of bumblebee wormhole

In this work, we calculate the quasi-normal frequencies from a bumblebee traversable wormhole. The bumblebee wormhole model is based on the bumblebee gravity, which exhibits a spontaneous Lorentz symmetry breaking. Supporting by the Lorentz violation parameter $λ$, this model allows the fulfillment of the flare-out and energy conditions, granted non-exotic matter to the wormhole. We analyze the parameters of bumblebee wormhole in order to obtain a Reege-Wheeler's equation with a bell-shaped potential. We obtain the quasi-normal modes (QNMs) via the WKB approximation method for both scalar and gravitational perturbations. All frequencies obtained are stable and the time domain profiles have decreasing oscillation (damping) profiles for the bumblebee wormhole.

gr-qc↗

arXiv2018

Monopoles on string-like models and the Coulomb's law

The t'Hooft-Polyakov monopole mass can be substantially altered, in the thick GS and HC brane-world setup, and can be employed to constrain the brane thickness limit. In this work, we comprise a brief review regarding gauge fields localization in the string-like six dimensional brane-world models setup. The correction to the Coulomb's law in two models is studied. Besides, the monopole features are investigated from the point of view of the gauge fields localization in the string-like brane-worlds and its thickness.

hep-th↗

arXiv2017

Graviton KK resonant mode in the correction of the Newton's law from 6D braneworlds

In this work, we derive an expression for the correction in the Newton's law of gravitation due to the gravitational Kaluza-Klein states in a general thick string-like braneworld scenario in six dimensions. In order to analyze corrections to Newton's law we study the gravity fluctuations in a 3-brane placed in a transverse resolved conifold and use suitable numerical methods to attain the massive spectrum and the corresponding eigenfunctions. Such braneworld model has a resolution parameter which removes the conical singularity. The correction has an exponentially suppressed mass term and depends on the values of the eigenfunctions and warp factors computed at the core peak of the brane. The spectrum is real and monotonically increased, as desired. However, the resolution parameter must assume moderate values to have physically acceptable states. Moreover, the trapped massless mode regains the 4D gravity and it is displaced from the origin, sharing similar profile with the energy density of brane for small values of resolution parameter. Finally, for the singular conifold, we found that a non-first eigenstate is a resonant mode. Such excited state is the largest contributor to corrections in the Newtonian potential.

hep-th↗

arXiv2017

Phase transitions in thick branes endorsed by entropic information

The so-called configurational entropy (CE) framework has proved to be an efficient instrument to study nonlinear scalar field models featuring solutions with spatially-localized energy, since its proposal by Gleiser and Stamapoulos. Therefore, in this work, we apply this new physical quantity in order to investigate the properties of degenerate Bloch branes. We show that it is possible to construct a configurational entropy measure in functional space from the field configurations, where a complete set of exact solutions for the model studied displays both double and single-kink configurations. Our study shows a rich internal structure of the configurations, where we observe that the field configurations undergo a quick phase transition, which is endorsed by information entropy. Furthermore, the Bloch configurational entropy is employed to demonstrate a high organisational degree in the structure of the configurations of the system, stating that there is a best ordering for the solutions.

hep-th↗

arXiv2017

Exotic Elko on String-Like Defects in Six Dimensions

We analyse the trapping of eigenspinors of the charge conjugation operator with dual helicity (Elko), in thin and thick string-like models with codimension-2. Elko spinor fields describe mass dimension one fermions in four dimensions (and, correspondingly, mass dimension two fermions in six dimensions), that represent natural dark matter prime candidates. This dark spinor has many applications, from particle physics to cosmology. On the other hand, six-dimensional brane-world models have, among other prominent features, the spontaneous confinement of free spin 1 fields and a mechanism that explains the mass hierarchy of fundamental fermions. In this paper, we use scalar couplings in order to confine the zero mode of Elko in six dimensions. Moreover, we use the Elko dark spinor features to propose an exotic coupling in order to remove the complex-valued terms in the massive Kaluza-Klein modes. Hence, we show that six dimensional models can resolve the main issues of Elko fields confinement presented in five dimensions.

hep-th↗

arXiv2016

Multiresonance modes in sine-Gordon brane models

In this work, we study the localization of the vector gauge field in two five-dimensional braneworlds generated by scalar fields coupled to gravity. The sine-Gordon like potentials are employed to produce different thick brane setups. A zero mode localized is obtained, and we show the existence of reverberations with the wave solutions indicating a quasi-localized massive mode. More interesting results are achieved when we propose a double sine-Gordon potential to the scalar field. The resulting thick brane shows a more detailed topology with the presence of an internal structure composed by two kinks. The massive spectrum of the gauge field is revalued on this scenario revealing the existence of various resonant modes. Furthermore, we compute the corrections to Coulomb law coming from these massive KK vector modes in these thick scenarios, where is concluded that the dilaton parameter regulates these corrections.

hep-th↗

arXiv2016

Refinements of the Weyl pure geometrical thick branes from information-entropic measure

This letter aims to analyse the so-called configurational entropy in the Weyl pure geometrical thick brane model. The Weyl structure plays a prominent role in the thickness of this model. We find a set of parameters associated to the brane width where the configurational entropy exhibits critical points. Furthermore, we show, by means of this information-theoretical measure, that a stricter bound on the parameter of Weyl pure geometrical brane model arises from the CE.

hep-th↗

arXiv2016

Bounds on topological Abelian string-vortex and string-cigar from information-entropic measure

In this work we obtain bounds on the topological Abelian string-vortex and on the string-cigar, by using a new measure of configurational complexity, known as configurational entropy. In this way, the information-theoretical measure of six-dimensional braneworlds scenarios are capable to probe situations where the parameters responsible for the brane thickness are arbitrary. The so-called configurational entropy (CE) selects the best value of the parameter in the model. This is accomplished by minimizing the CE, namely, by selecting the most appropriate parameters in the model that correspond to the most organized system, based upon the Shannon information theory. This information-theoretical measure of complexity provides a complementary perspective to situations where strictly energy-based arguments are inconclusive. We show that the higher the energy the higher the CE, what shows an important correlation between the energy of the a localized field configuration and its associated entropic measure.

hep-th↗

arXiv2015

Fermionic Kaluza-Klein modes in the string-cigar braneworld

We study the spin 1/2 and spin 3/2 fermion fields in a thick braneworld scenario in six dimensions called string-cigar model. This smooth string-like model has a source that satisfies the dominant energy condition and undergoes a Ricci flow. We propose a new coupling for the fermions with a background gauge field which allows a smooth and normalized massless mode in the brane with positive tension. By numerical methods the mass spectrum and the massive eigenfunctions are obtained. The Kaluza-Klein massive tower exhibits the usual increasing pattern and, in this scenario, the coupling term does not allow tachyonic Kaluza-Klein states. The brane core and the background gauge field alter the properties of the massive KK tower, enhancing the amplitude of the massive states near the origin and changing the properties of the analogue Schroedinger potential. Furthermore, we find massive modes as resonant states in this scenario for both fermionic fields.

hep-th↗

arXiv2014

Vector and fermion fields on a bouncing brane with a decreasing warp factor in a string-like defect

In a recent work, a model has been proposed where a brane is made of a scalar field with bounce-type configurations and embedded in a bulk with a string-like metric. This model produces an AdS scenario where the components of the energy momentum tensor are finite and have its positivity ensured by a suitable choice of the bounce configurations. In the present work, we study the issue of gauge and fermion field localization in this scenario. In contrast with the five dimensional case here the gauge field is localized without the dilaton contribution. Nevertheless, it is remarkable that the localization of the fermion field depends on the introduction of a minimal coupling with the angular component of the gauge field, which differs clearly from five dimensional scenarios. Furthermore, we perform a qualitative analysis of the fermionic massive modes and conclude that only left handed fermions could be localized in the brane.

hep-th↗

arXiv2013

Fermions in a warped resolved conifold

We investigated the localization of the spinorial field in a braneworld built as a warped product between a 3-brane and a 2-cycle of the resolved conifold. This scenario provides a geometric flow that controls the singularity at the origin and changes the properties of the fermion in this background. Furthermore, due the cylindrical symmetry according to the 3-brane and a smoothed warp factor, this geometry can be regarded as a near brane correction of the string-like branes. This geometry allows a normalizable and well-defined massless mode whose decay and value on the brane depend on the resolution parameter. For the Kaluza-Klein modes, resolution parameter also controls the height of the barrier of the volcano potential.

hep-th↗