arXiv subjects

R. da Rocha

Publications and source records attributed to R. da Rocha.

At least 55 records · Page 3Linked to original sources

arXiv2020

Exotic fermionic fields and minimal length

We investigate the effective Dirac equation, corrected by merging two scenarios that are expected to emerge towards the quantum gravity scale. Namely, the existence of a minimal length, implemented by the generalized uncertainty principle, and exotic spinors, associated with any non-trivial topology equipping the spacetime manifold. We show that the free fermionic dynamical equations, within the context of a minimal length, just allow for trivial solutions, a feature that is not shared by dynamical equations for exotic spinors. In fact, in this coalescing setup, the exoticity is shown to prevent the Dirac operator to be injective, allowing the existence of non-trivial solutions.

hep-th↗

arXiv2020

AdS$_5$-Schwarzschild deformed black branes and hydrodynamic transport coefficients

A family of deformed AdS$_5$-Schwarzschild black branes is here derived, employing the membrane paradigm of AdS/CFT. The solution of the Einstein-Hilbert action, with the Gibbons-Hawking term and a counter-term that eliminates eventual divergences, yields a partition function associated with the dual theory which allows the computation of the entropy, pressure and free energy, as state functions, in the canonical ensemble. AdS/CFT near-horizon methods are then implemented to compute the shear viscosity-to-entropy ratio, then restricting the range of the parameter that defines a family of deformed black branes.

hep-th↗

arXiv2020

Deformed AdS4-Reissner-Nordström black branes and shear viscosity-to-entropy density ratio

A family of deformed AdS4-Reissner-Nordström black branes, governed by a free parameter, is derived using the ADM formalism, in the context of the membrane paradigm. Their new event horizons, the Hawking temperature and other aspects are scrutinized. AdS/CFT near-horizon methods are then implemented to compute the shear viscosity-to-entropy ratio for the deformed AdS4-Reissner-Nordström metric. The Killing equation is shown to yield new values for the free parameter and the shear viscosity-to-entropy ratio is used to derive a reliable range for tidal charge.

hep-th↗

arXiv2020

Hearing the shape of inequivalent spin structures and exotic Dirac operators

Exotic spinor fields arise from inequivalent spin structures on non-trivial topological manifolds, $M$. This induces an additional term in the Dirac operator, defined by the cohomology group $H^1(M,\mathbb{Z}_2)$ that rules a Cech cohomology class. This formalism is extended for manifolds of any finite dimension, endowed with a metric of arbitrary signature. The exotic corrections to heat kernel coefficients, relating spectral properties of exotic Dirac operators to the geometric invariants of $M$, are derived and scrutinized.

hep-th↗

arXiv2020

Spinor symmetries and underlying properties

By exploring a spinor space whose elements carry a spin 1/2 representation of the Lorentz group and satisfy the the Fierz-Pauli-Kofink identities we show that certain symmetries operations form a Lie group. Moreover, we discuss the reflex of the Dirac dynamics in the spinor space. In particular, we show that the usual dynamics for massless spinors in the spacetime is related to an incompressible fluid behavior in the spinor space.

math-ph↗

arXiv2019

Holographic entanglement entropy under the minimal geometric deformation and extensions

The holographic entanglement entropy (HEE) of the minimal geometrical deformation (MGD) procedure and extensions (EMGD), is scrutinized within the membrane paradigm of AdS/CFT. The HEE corrections of the Schwarzschild and Reissner--Nordström solutions, due to a finite fluid brane tension, are then derived and discussed in the context of the MGD and the EMGD.

hep-th↗

arXiv2019

Pion family in AdS/QCD: the next generation from configurational entropy

The two flavour AdS/QCD, with chiral and gluon condensates, sets in the description of the pion family and its mass spectra. Using gravity-dilaton-gluon backgrounds, entropic Regge-like trajectories for the pion family are then derived. They relate the $π$ mesons underlying configurational entropy to both the pions excitation wave mode number and the pions experimental mass spectra, yielding a reliable prediction for the mass spectra of higher excitation pion modes, to be experimentally detected.

hep-th↗

arXiv2019

Extended quantum portrait of MGD black holes and information entropy

The extended minimal geometric deformation (EMGD) is employed on the fluid membrane paradigm, to describe compact stellar objects as Bose--Einstein condensates (BEC) consisting of gravitons. The black hole quantum portrait, besides deriving a preciser phenomenological bound for the fluid brane tension, is then scrutinized from the point of view of the configurational entropy. It yields a range for the critical density of the EMGD BEC, whose configurational entropy has global minima suggesting the configurational stability of the EMGD BEC.

hep-th↗

arXiv2018

Informational entropic Regge trajectories of meson families in AdS/QCD

Bulk mesons propagating in chiral and gluon condensates, in a gravity background, are scrutinized in holographic soft wall AdS/QCD models, involving deformed dilatonic backgrounds. The configurational entropy of the $a_1$ axial vector, the $ρ$ vector, and the $f_0$ scalar meson families is then computed. Two types of informational entropic Regge trajectories are then obtained, where the logarithm of the mesons configurational entropy is expressed in terms of both the experimental meson mass spectra and their excitation number as well. Therefore the mass spectra of the next generation of elements in each meson family, besides being predicted as eigenvalues of Schrödinger-like equations, are estimated with better accuracy and discussed.

hep-th↗

arXiv2018

The emergence of flagpole and flag-dipole fermions in fluid/gravity correspondence

The emergence of flagpole and flag-dipole singular spinor fields is explored, in the context of fermionic sectors of fluid/gravity correspondence, arising from the duality between the gravitino, in supergravity, and the phonino, in supersymmetric hydrodynamics. Generalized black branes, whose particular case consists of the AdS--Schwarzschild black brane, are regarded. The correspondence between hydrodynamic transport coefficients, and the universal absorption cross sections of the generalized black branes, is extended to fermionic sectors, including supersound diffusion constants. A free parameter, in the generalized black brane solution, is shown to control the flipping between regular and singular fermionic solutions of the equations of motion for the gravitino.

hep-th↗

arXiv2018

New spinor classes on the Graf-Clifford algebra

Pinor and spinor fields are sections of the subbundles whose fibers are the representation spaces of the Clifford algebra of the forms, equipped with the Graf product. In this context, pinors and spinors are here considered and the geometric generalized Fierz identities provide the necessary framework to derive and construct new spinor classes on the space of smooth sections of the exterior bundle, endowed with the Graf product, for prominent specific signatures, whose applications are discussed.

math-ph↗

arXiv2018

The Graf product: a Clifford structure framework on the exterior bundle

The geometric product, defined by Graf on the space of differential forms, endows the sections of the exterior bundle by a structure that is necessary to construct a Clifford algebra. The Graf product is introduced and revisited with a suitable underlying framework that naturally encompasses a coframe in the cotangent bundle, besides the volume element centrality, the Hodge operator and the so called truncated subalgebra as well.

math.DG↗

arXiv2018

Dynamical tachyonic AdS/QCD and information entropy

The configurational entropy setup is employed to study dynamical tachyonic holographic AdS/QCD models. The phenomenology of light-flavour mesonic states is then corroborated by the Shannon's information. Tachyonic bulk corrections to the dynamical AdS/QCD show more dominant and abundant dual mesonic states in the 4D boundary QCD, when compared to the dual mesons in the standard dynamical AdS/QCD. Entropic Regge-like trajectories are also emulated.

hep-th↗

arXiv2018

Gregory-Laflamme analysis of MGD black strings

The minimal geometric deformation (MGD), associated with the 4D Schwarzschild solution of the Einstein equations, is shown to be a solution of the pure 4D Ricci quadratic gravity theory, whose linear perturbations are then implemented by the Gregory-Laflamme eigentensors of the Lichnerowicz operator. The stability of MGD black strings is hence studied, through the correspondence between their Lichnerowicz eigenmodes and the ones associated with the 4D MGD solutions. Its is shown that there exists a critical mass driving the MGD black strings stability, above which the MGD black string is precluded from any Gregory-Laflamme instability. The general relativistic limit leads the MGD black string to be unstable, as expected, corresponding to the standard Gregory-Laflamme black string instability.

hep-th↗

arXiv2018

The extended minimal geometric deformation of SU($N$) dark glueball condensates

The extended minimal geometric deformation (EMGD) procedure, in the holographic membrane paradigm, is employed to model stellar distributions that arise upon self-interacting scalar glueball dark matter condensation. Such scalar glueballs are SU($N$) Yang-Mills hidden sectors beyond the Standard Model. Then, corrections to the gravitational wave radiation, emitted by SU($N$) EMGD dark glueball stars mergers, are derived, and their respective spectra are studied in the EMGD framework, due to a phenomenological brane tension with finite value. The bulk Weyl fluid that drives the EMGD is then proposed to be experimentally detected by enhanced windows at the eLISA and LIGO.

hep-th↗

arXiv2018

Opening the Pandora's box of quantum spinor fields

Lounesto's classification of spinors is a comprehensive and exhaustive algorithm that, based on the bilinears covariants, discloses the possibility of a large variety of spinors, comprising regular and singular spinors and their unexpected applications in physics and including the cases of Dirac, Weyl, and Majorana as very particular spinor fields. In this paper we pose the problem of an analogous classification in the framework of second quantization. We first discuss in general the nature of the problem. Then we start the analysis of two basic bilinear covariants, the scalar and pseudoscalar, in the second quantized setup, with expressions applicable to the quantum field theory extended to all types of spinors. One can see that an ampler set of possibilities opens up with respect to the classical case. A quantum reconstruction algorithm is also proposed. The Feynman propagator is extended for spinors in all classes.

hep-th↗

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

Information-entropic analysis of Korteweg--de Vries solitons in the quark-gluon plasma

Solitary waves propagation of baryonic density perturbations, ruled by the Korteweg--de Vries equation in a mean-field quark-gluon plasma model, are investigated from the point of view of the theory of information. A recently proposed continuous logarithmic measure of information, called configurational entropy, is used to derive the soliton width, defining the pulse, for which the informational content of the soliton spatial profile is more compressed, in the Shannon's sense.

hep-ph↗