arXiv subjects

Edilberto O. Silva

Publications and source records attributed to Edilberto O. Silva.

At least 55 records · Page 3Linked to original sources

arXiv2026

ModMax-AdS Black Hole with Global Monopole as Source in Kalb-Ramond Gravity

In this work, we investigate in detail the thermodynamic properties of a spherically symmetric ModMax-AdS black hole sourced by a global monopole within the Kalb-Ramond gravity. We derive the key thermodynamic quantities, including the Hawking temperature, Gibbs free energy, and specific heat capacity, and analyze how the geometric parameters influence these physical quantities. The first law of thermodynamics and the corresponding Smarr formula are explicitly verified. Furthermore, we study the thermodynamic criticality of the system by deriving the critical points and examining the effects of the space-time geometric parameters. We also obtain the inversion temperature and demonstrate that the minimum inversion temperature is modified by the space-time parameters. In addition, the sparsity of Hawking radiation and thermal fluctuations of the system are investigated, highlighting the effects of the parameters on the entropy corrections. Finally, we analyze the optical properties of the black hole, in particular the photon sphere and shadow radius, showing how these parameters influence these features.

gr-qc↗

arXiv2026

Thermal Analysis, Joule-Thomson Expansion and Hawking Sparsity of Mod(A)Max-AdS Black Hole Immersed in a Cloud of Strings

We investigate the thermodynamic behavior of a spherically symmetric Anti-de Sitter black hole in Mod(A)Max electrodynamics surrounded by a cloud of strings. Within the extended phase-space framework, we treat the cosmological constant as a pressure and interpret the black-hole mass as enthalpy, which enables a unified discussion of local stability, global phase structure, and Joule--Thomson expansion. We analyze the Hawking temperature, Gibbs free energy, and heat capacity, and show how the string-cloud parameter, the Mod(A)Max deformation, and the electric charge reshape the physical domain, the stability windows, and the small/large black-hole transition pattern. We further characterize the critical behavior and demonstrate that a van der Waals--like phase structure arises only in the physical sector, while the alternate branch does not admit a genuine critical point. For the Joule-Thomson process, we determine the inversion curve and the corresponding isenthalpic trajectories, highlighting how the model parameters control the cooling/heating regimes and can generate terminating isenthalpic behavior at sufficiently large charge. Finally, we examine the sparsity of Hawking radiation and discuss how the underlying parameters influence the temporal discreteness of the emitted flux, particularly near extremality and in the large-radius AdS regime.

physics.gen-ph↗

arXiv2026

Geodesic Structure, Thermodynamics and Scalar Perturbations of Mod(A)Max black hole Surrounded by Perfect Fluid Dark Matter

In this work, we investigate the optical properties of a spherically symmetric Mod(A)Max black hole surrounded by perfect fluid dark matter, focusing on key features such as the photon sphere radius, shadow, photon trajectories, and the effective radial force experienced by photons. We also study the dynamics of massive particles around the black hole, deriving the effective potential and, from it, the specific energy and angular momentum of particles moving in circular orbits of fixed radii is discussed. The conditions for marginally stable circular orbits are analyzed, highlighting how the geometric parameters that modify the spacetime curvature influence both the optical and dynamical features. Furthermore, we explore the thermodynamic behavior of the black hole by examining its temperature, Gibbs free energy, and heat capacity, as well as its thermodynamic topology. Finally, scalar field perturbations are considered through the massless Klein-Gordon equation, and the quasinormal modes (QNMs) in the eikonal regime are computed, illustrating how the geometric parameters affect the potential and the QNM spectra.

gr-qc↗

arXiv2026

Quantum scattering in helically twisted geometries: Coulomb-like interaction and Aharonov-Bohm effect

We investigate the scattering of a charged quantum particle in a helically twisted background that induces an effective Coulomb-like interaction, in the presence of an Aharonov-Bohm (AB) flux. Starting from the nonrelativistic Schrödinger equation in the twisted metric, we derive the radial equation and show that, after including the AB potential, it can be mapped onto the same Kummer-type differential equation that governs the planar $2D$ Coulomb $+$ AB problem, with a geometry-induced Coulomb strength and the azimuthal quantum number shifted as $m\to m-λ$. We construct the exact scattering solutions, obtain closed expressions for the partial-wave $S$ matrix and phase shifts, and derive the corresponding scattering amplitude, differential cross section, and total cross section. We also show that the pole structure of the $S$ matrix is consistent with the bound-state quantization previously obtained for the helically twisted Coulomb-like problem.

quant-ph↗

arXiv2026

Observable Optical Signatures, Particle Dynamics and Epicyclic Frequencies of Mod(A)Max Black Holes

In this work, we investigate the observable optical signatures of the Mod(A)Max black hole spacetime. We analyze key optical features, including the photon sphere, black hole shadow, and photon trajectories, and examine how these observables depend on the underlying geometric parameters, such as the electric charge and the Mod(A)Max coupling parameter. We further study the dynamics of neutral test particles in the vicinity of the black hole by deriving the effective potential within the Hamiltonian formalism. Using this potential, we obtain the specific energy and specific angular momentum for test particles on circular orbits of fixed radius, as well as the innermost stable circular orbit (ISCO), and explore how the geometric parameters influence these quantities and the ISCO radius. Finally, we derive the epicyclic (azimuthal, radial, and vertical) frequencies to analyze quasi-periodic oscillations (QPOs) exploring how the geometric parameters influences these and discuss their physical implications.

gr-qc↗

arXiv2026

Geometrical optical activity induced by a continuous distribution of screw dislocations

We study light propagation in a medium with uniform torsion, modeled as a continuum of screw dislocations within the geometric theory of defects. By solving Maxwell's equations in covariant form, we show that torsion induces intrinsic chirality and circular birefringence: right- and left-circular polarizations acquire different wavenumbers, leading to a purely geometric optical activity. The polarization plane of a linearly polarized beam rotates according to the simple law $Δθ= ΩρL$, linear in the dislocation density $Ω$, propagation length $L$, and transverse coordinate $ρ$. This can be recast as an effective birefringence $Δn = 2cΩρ/ω$, providing geometric design rules for torsion-induced rotatory power. Using parameters from dislocated semiconductors, we obtain millidegree rotations over millimetre-scale paths, within reach of modern polarimetric techniques and amenable to enhancement in metamaterial platforms. We also show that the same spiral geometry implements a broadband geometric phase gate for polarization qubits and has an electronic analogue on the surface of cylindrical topological insulators, where torsion shears the Dirac cone, establishing a unified geometric link between torsion, optical activity, and topological electronic responses.

physics.optics↗

arXiv2026

The Dirac equation: historical context, comparisons with the Schrödinger and Klein-Gordon equations, and elementary consequences

This paper offers educational insight into the Dirac equation, examining its historical context and contrasting it with the earlier Schrödinger and Klein-Gordon (KG) equations. The comparison highlights their Lorentz transformation symmetry and potential probabilistic interpretations. We explicitly solve the free-particle dynamics in Dirac's model, revealing the emergence of negative-energy solutions. This discussion examines the Dirac Sea Hypothesis and explores the solutions' inherent helicity. Additionally, we demonstrate how the Dirac equation accounts for spin and derive the Pauli equation in the non-relativistic limit. The Foldy-Wouthuysen transformation reveals how the equation incorporates spin-orbit interaction and other relativistic effects, ultimately leading to the fine structure of hydrogen. A section on relativistic covariant notation is included to emphasize the invariance of the Dirac equation, along with more refined formulations of both the KG and Dirac equations. Designed for undergraduate students interested in the Dirac equation, this resource provides a historical perspective without being purely theoretical. Our approach underscores the significance of a pedagogical method that combines historical and comparative elements to profoundly understand the role of the Dirac equation in modern physics.

physics.gen-ph↗

arXiv2025

Thermodynamic geometry of charged AdS black holes with a string cloud in Lorentz-violating Einstein-Kalb-Ramond gravity

We investigate the thermodynamic microstructure of electrically charged AdS black holes in Einstein-Kalb-Ramond bumblebee gravity in the presence of a spherically symmetric cloud of strings. Employing Weinhold and Ruppeiner thermodynamic geometries in complementary thermodynamic representations, we show that curvature singularities consistently track the spinodal boundaries and the second-order critical point associated with a Van der Waals-like small/large black-hole phase transition. Moreover, the sign structure of the Ruppeiner curvature provides a transparent characterization of the competing microscopic interactions across the coexisting phases. We find that the Lorentz-violating parameter $\ell$ and the string-cloud parameter $α$ shift the critical scales and rescale correlation measures while preserving the universality class of the critical behavior. We further comment on dynamical and holographic implications and contrast the thermodynamic sensitivity to $(\ell,α)$ with thin-disk optical signatures.

hep-th↗

arXiv2025

Thermodynamics and $P$-$V$ Criticality of Charged AdS Black Holes with a Cloud of Strings in Kalb-Ramond Gravity

We investigate the extended phase-space thermodynamics and $P$--$V$ criticality of electrically charged anti-de Sitter (AdS) black holes in Kalb--Ramond bumblebee gravity in the presence of a spherically symmetric cloud of strings. The background Kalb--Ramond field induces Lorentz symmetry violation through a dimensionless parameter $\ell$, while the string cloud is characterized by a parameter $α$, both entering the lapse function and deforming the geometry. Interpreting the ADM mass as enthalpy, we derive the main thermodynamic quantities, Hawking temperature, entropy, thermodynamic volume, Gibbs free energy, internal energy, and specific heat, and analyze how $(\ell,α)$ jointly affect stability and phase structure. We obtain a Van der Waals--type equation of state, compute the critical point $(P_c,T_c,v_c)$, and show that, although the critical scales depend nontrivially on $\ell$ and $α$, the universal ratio $P_c v_c/T_c = 3/8$ is preserved. Using the thermodynamic topology approach, we determine that the total topological charge of the black hole solution remains $W=1$, placing it in the same topological class as the Reissner--Nordström--AdS black hole. Finally, by studying the Joule--Thomson expansion, we derive the inversion curve and find that the minimal inversion temperature satisfies $T_i^{\rm min}/T_c = 1/2$, as in the Reissner--Nordström--AdS case, indicating that Lorentz violation and the string cloud deform the thermodynamic scales without changing the underlying universality class.

hep-th↗

arXiv2025

Screw-dislocation-engineered quantum dot: geometry-tunable nonlinear optics, orbital qubit addressability, and torsion metrology

We study a single electron confined in a uniform-torsion medium, a continuum model of a screw dislocation density, in a perpendicular magnetic field, and in the presence of an Aharonov--Bohm flux. Torsion alone produces radial confinement without any \textit{ad hoc} potential, while the Aharonov--Bohm phase breaks the usual $m\leftrightarrow -m$ symmetry. From the exact spectrum and wave functions, we find: (i) a torsion-controlled optical transition whose energy blue-shifts from $\sim 6.8$ to $\sim 15.5$~meV and whose saturation intensity varies by an order of magnitude, enabling geometry-programmable optical switching; (ii) an Aharonov--Bohm-tunable ``angular pseudospin'' formed by the $m=\pm1$ states, with flux-controlled level splitting and asymmetric oscillator strengths that allow selective optical addressability; and (iii) an approximately linear torsion dependence of the transition energy that enables nanoscale torsion metrology with an estimated resolution of $\sim 10^{5}~\mathrm{m}^{-1}$. In this context, ``torsion'' refers to the experimentally relevant continuum limit of a uniform density of parallel screw dislocations, i.e., a crystal with finite torsion but vanishing curvature, which can, in practice, be engineered and probed in twisted nanowires and strained semiconductor heterostructures. We also show how torsion provides \textit{in situ} control of emitter--cavity detuning and light--matter coupling in cavity QED, in direct analogy with strain tuning of semiconductor quantum dots in nanocavities, but here arising from a purely geometric/topological parameter.

cond-mat.mes-hall↗

arXiv2025

Bounds on Lorentz-violating parameters in magnetically confined 2D systems: A phenomenological approach

We present a unified, SI-consistent framework to constrain minimal SME coefficients $a_μ$ and $b_μ$ using magnetically confined two-dimensional electron systems under a uniform magnetic field. Working in the nonrelativistic (Schrödinger--Pauli) limit with effective mass, we derive the radial problem for cylindrical geometries and identify how spatial components ($\mathbf a,\mathbf b$) reshape the effective potential, via $1/r$ and $r$ terms or spin-selective offsets, while scalar components ($a_0,b_0$) act through a global energy shift and a spin-momentum coupling. Phenomenological upper bounds follow from requiring LV-induced shifts to lie below typical spectroscopic resolutions: $|a_0|\lesssimδE$, $|b_z|\lesssimδE/\hbar$, and compact expressions for $|a_φ|$ and $|b_0|$ that expose their dependence on device scales ($r_0$, $B_0$, $μ$, $m$). Dimensional analysis clarifies that, in this regime, spatial $a_i$ carry momentum dimension and $b_i$ carry inverse-time/length dimensions, ensuring gauge-independent, unit-consistent reporting. Finite-difference eigenvalue calculations validate the scaling laws and illustrate spectral signatures across realistic parameter sets. The results show that scalar sectors (notably $a_0$) are tightly constrained by state-of-the-art $μ$eV-resolution probes, while spatial and axial sectors benefit from spin- and $m$-resolved spectroscopy and geometric leverage, providing a reproducible pathway to test Lorentz symmetry in condensed-matter platforms.

cond-mat.mes-hall↗

arXiv2025

Nonlinear optical behavior of confined electrons under torsion and magnetic fields

In this work, we investigate the influence of torsion, Aharonov-Bohm flux, and external magnetic fields on the linear and nonlinear optical properties of a confined quantum system. The confinement potential is not assumed a priori, but emerges as a radial effective potential, analogous to a quantum dot, geometrically induced by the torsion of the material. Starting from an effective radial equation derived in a nontrivial geometric background, we analytically solve for the energy spectrum and wave functions. These solutions are then employed to evaluate the optical absorption coefficients and refractive index changes, including both linear and third-order nonlinear contributions. The formalism incorporates the electric dipole approximation and accounts for intensity-dependent effects such as saturation and spectral shifts. Our results reveal that torsion and topological parameters significantly modify the optical response, leading to tunable resonances and nontrivial dispersive behavior. This work highlights the potential of geometric and topological engineering in low-dimensional systems to control and enhance nonlinear optical phenomena.

physics.optics↗

arXiv2025

Letelier-AdS Black Hole Surrounded by a Perfect Fluid Dark Matter in the presence of Quintessence

This study investigates a Schwarzschild-anti de Sitter black hole coupled to a cloud of strings featuring only the electric-like component of the string bivector, embedded in a perfect fluid dark matter and a quintessence field. We examine the dynamics of photons and massive particles, focusing on trajectories, photon spheres, BH shadows, their topological characteristics, and innermost stable circular orbits (ISCOs), and emphasizing the influence of string cloud, perfect-fluid dark matter, and quintessence-like field parameters. Additionally, we explore the black hole's thermodynamics, deriving the Hawking temperature, Gibbs free energy, and specific heat, and discuss the modified first law of thermodynamics and thermodynamic topology under external matter fields. We demonstrate that the presence of a string cloud, perfect-fluid dark matter, and a quintessence-like field together modifies the geodesic structure and thermodynamic properties, thereby shifting the results relative to the standard Schwarzschild BH solution.

gr-qc↗

arXiv2025

Single-Scale Magnetoelastic Landau Quantization: Thermodynamics, Quantum Oscillations, and Metrology

We develop a unified, single-scale description of thermodynamics and quantum oscillations in electronic systems with a uniform areal density of screw dislocations under a uniform magnetic field. A single tunable gap, $\hbar|ω_{eff}|$ with $ω_{eff}=ω_{c}+ω_{cl}$, organizes all equilibrium observables obtained from a compact harmonic-oscillator partition function: free energy, internal energy, entropy, heat capacity, magnetization, magnetic susceptibility, and magnetocaloric responses collapse onto universal hyperbolic kernels in $x=\hbar|ω_{eff}|/(2k_{B}T)$. We identify a compensated-field regime where the transverse gap closes and the heat capacity reaches an equipartition plateau, providing a sharp signature of magnetoelastic interference. In transport and torque, the same scale rigidly shifts the Hall fan and compresses the $1/B$ period of de Haas-van Alphen and Shubnikov-de Haas oscillations when expressed in $1/B_{eff}$, enabling a phase-unwarping protocol that metrologizes the dislocation density from a single field sweep. In mesoscopic samples, boundary corrections to the Landau degeneracy generate finite-size calorimetric oscillations that diagnose the effective magnetic length. Moderate disorder and weak interactions preserve the kernel structure while smoothing amplitudes. We outline an experimental roadmap combining on-chip calorimetry, torque magnetometry, and transport, and discuss device-level opportunities in caloritronics and strain engineering, magnetocaloric microcooling, magnetoelastic heat switching, and dilatometric transduction, where the single scale $\hbar|ω_{eff}|$ enables rational design and optimization.

cond-mat.mes-hall↗

arXiv2025

Schwarzschild Black Hole Coupled with a Cloud of Strings Immersed in King Dark Matter Halo

In this paper, we examine the geodesic and thermodynamic properties of a Schwarzschild black hole with a cloud of strings (known as the Letelier black hole) immersed in a King dark matter (KDM) halo under an isotropic configuration. The dynamics of both photons and massive particles are analyzed in detail using the effective potential formalism, including particle trajectories, the photon sphere, black hole shadow, and the innermost stable circular orbits (ISCOs). Particular emphasis is placed on how the presence of the KDM halo modifies these geometric and dynamical features. Furthermore, we explore the topological characteristics of photon rings by constructing a normalized vector field, following Duan\textquotesingle{}s topological current $ϕ$-mapping theory, and demonstrate how this field is influenced by both the string cloud and the KDM halo. In the thermodynamic context, we analyze the impact of the KDM halo and the string cloud on the Hawking temperature, Gibbs free energy, thermal stability, and phase transitions of the black hole. Finally, we examine the thermodynamic topology of the system using a theoretical framework that incorporates a generalized Helmholtz free energy and topological current theory. In both the photon sphere and thermodynamic analyses, we show that the string cloud parameter shifts the location of the zero point of the vector field in the equatorial plane. Specifically, in the photon sphere case, the radius of the photon sphere increases with increasing values of the string cloud parameter, while in the thermodynamic topology, the horizon radius decreases as the string cloud parameter increases.

gr-qc↗

arXiv2025

Nonrelativistic quantum dynamics in a twisted screw spacetime

We investigate the nonrelativistic quantum dynamics of a spinless particle in a screw-type spacetime endowed with two independent twist controls that interpolate between a pure screw dislocation and a homogeneous twist. From the induced spatial metric we build the covariant Schrödinger operator, separate variables to obtain a single radial eigenproblem, and include a uniform magnetic field and an Aharonov-Bohm (AB) flux by minimal coupling. Analytically, we identify a clean separation between a global, AB-like reindexing set by the screw parameter and a local, curvature-driven mixing generated by the distributed twist. We derive the continuity equation and closed expressions for the azimuthal and axial probability currents, establish practical parameter scalings, and recover limiting benchmarks (AB, Landau, and flat space). Numerically, a finite-difference Sturm-Liouville solver (with core excision near the axis and Langer transform) resolves spectra, wave functions, and currents. The results reveal AB periodicity and reindexing with the screw parameter, Landau-fan trends, twist-induced level tilts and avoided crossings, and a geometry-induced near-axis backflow of the axial current with negligible weight in cross-section integrals. The framework maps the geometry and fields directly onto measurable spectral shifts, interferometric phases, and persistent-current signals.

quant-ph↗

arXiv2025

Black Hole Solution in Anti-de Sitter Space with a New Cloud of Strings Surrounded by Dark Matter Halo

This paper presents a comprehensive theoretical study of a Schwarzschild-like Anti-de Sitter (AdS) black hole (BH) influenced by a new cloud of strings (NCS) and a dark matter halo (DMH) characterized by a Dehnen-type density profile. We analyze the geodesic motion of both massless and massive test particles, highlighting how the NCS and DMH parameters affect the effective potentials, photon spheres, circular orbits, BH shadow, and the innermost stable circular orbit (ISCO) of test particles. Additionally, we investigate the thermodynamic behavior of the BH in an extended phase space by deriving key quantities, such as the Hawking temperature, the equation of state (EoS), Gibbs free energy, internal energy, and the specific heat capacity. Our results show that the presence of NCS and DMH induces significant modifications in both the dynamical and thermodynamical behavior of the BH, including shifts in the Hawking-Page transition and divergences in heat capacity, thereby reshaping the phase structure of the BH.

gr-qc↗

arXiv2025

AdS Black Hole Solution with a Dark Matter Halo Surrounded by a Cloud of Strings

We derive and analyze a Schwarzschild-like Anti-de Sitter (AdS) black hole (BH) obtained as a static, spherically symmetric solution of Einstein's equations sourced by a cloud of strings (CoS) and a dark matter (DM) halo modeled by a Dehnen-type density profile. We first study the geodesic motion of massless and massive test particles, emphasizing how the CoS parameter $α$ and the DM halo parameters $(ρ_s, r_s)$ influence photon spheres, circular orbits, the BH shadow, and the innermost stable circular orbit (ISCO). We then examine scalar perturbations via the effective potential and the associated quasinormal-mode (QNM) spectra, showing how $α$ and $(ρ_s, r_s)$ deform oscillation frequencies and damping rates, thereby affecting stability diagnostics. Furthermore, we investigate the thermodynamics in the extended phase space, deriving the Hawking temperature, equation of state, Gibbs free energy, and specific heat capacity, and establishing a consistent first law and Smarr relation with natural work terms for $α$ and $(ρ_s, r_s)$. We find that the interplay between the CoS and the DM halo produces quantitative and sometimes qualitative changes in both dynamical and thermodynamical properties, including shifts of the Hawking--Page transition and heat-capacity divergences, thus reshaping the phase structure of Schwarzschild--AdS BHs.

gr-qc↗