arXiv subjects

Edilberto O. Silva

Publications and source records attributed to Edilberto O. Silva.

At least 19 recordsLinked to original sources

arXiv2026

Circulation and operational sparsity of analogue Hawking radiation in rotating acoustic horizons

Temporal sparsity compares the mean interval between emitted quanta with a characteristic single-quantum timescale. We study this operational quantity for the rotating draining-bathtub acoustic horizon in two spatial dimensions. The Hawking temperature is fixed by the radial drain and does not depend on circulation, while the geometric capture width and the transmission spectrum do. A geometric black-body benchmark therefore predicts reduced temporal separation as circulation increases. We then solve the radial scattering problem and compute converged greybody-corrected number and energy fluxes, including the superradiant sector. At a circulation-to-drain ratio of unity, the thermal-clock sparsity is 0.44 whereas the spectrum-based sparsity is 1.82. The former crosses the temporal-overlap benchmark near a ratio of 0.40, while the latter remains above unity at all sampled circulation ratios. We also show that the binned sparsity definition is logarithmically infrared sensitive in two spatial dimensions. Rotation therefore enhances the number flux while hardening the spectrum, making temporal overlap intrinsically dependent on the operational clock used to resolve the emitted quanta.

gr-qc↗

arXiv2026

Electric and magnetic Penrose processes, charged-particle collisions and superradiance around a Lorentz-violating dyonic black hole

This paper is aimed at investigating electromagnetic energy extraction, charged-particle collisions, charged-field superradiance, and horizon stability in a Lorentz-violating dyonic Kalb-Ramond black hole. The geometry differs from the dyonic Reissner-Nordstr\"om solution through a modified asymptotic normalization and an effective charge combining electric and magnetic sectors. We derive the dynamics of electrically and magnetically charged probes, including monopole-induced conical motion, and formulate electric and magnetic Penrose processes as decay or collision mechanisms in which a negative-energy fragment falls into the horizon while another escapes with enhanced energy. The electric and magnetic channels are controlled by $\Phi_H=Q/[(1-\ell)r_+]$ and $\Psi_H=p/[(1-2\ell)r_+]$, respectively. Negative-energy states arise from electromagnetic canonical energy rather than from a geometrical ergoregion. We also obtain escape conditions for the outgoing products, test the possibility of overcharging or overmagnetizing the black hole, and analyze the center-of-mass energy of charged-particle collisions. Nonextremal same-direction collisions remain finite, whereas head-on or near-critical configurations can become large. In the extremal limit, electrically or magnetically critical particles may generate the Ba\~nados-Silk-West divergence when the radial reachability condition is fulfilled.

gr-qc↗

arXiv2026

Multipolar static tidal response of Schwarzschild black holes in cubic gravity: a metric-action derivation of tidal running

Static tidal Love numbers of four-dimensional Schwarzschild black holes vanish in general relativity, whereas higher-curvature interactions can generate a nontrivial response. We investigate the parity-even cubic Weyl correction directly in metric variables and derive the electric, static response for every integer multipole $\ell \geq 2$. Organizing the angular reduction through $L=\ell(\ell+1)$, we obtain exact radial actions and show that perturbative order reduction converts the three metric equations into a constrained two-dimensional first-order system. Eliminating one field yields a scalar equation whose homogeneous operator is precisely the general-relativistic static tidal operator. A Frobenius and Green-function analysis gives the gauge-invariant Zerilli--Moncrief running coefficient $\beta_{\ell}^{\rm ZM}=\epsilon_{\rm e}\,7L^{2}(L-2)^{2}(L-4)(L-6)/12$ and identifies the factor $L-6$ as the reason why the quadrupole is the unique physical electric multipole without logarithmic running. We solve the quadrupole exactly, obtaining the fixed-integer branch ratio $-2400\,\epsilon_{\rm e}$ and explaining why it differs from the analytically continued canonical Love number $k_{2}^{E}=448\,\epsilon_{\rm e}$. For the octupole, we construct the complete horizon-regular global metric solution and exhibit the cancellation of horizon logarithms between the two Green-function channels. Finally, we derive the normalization map to the canonical electric beta functions and the corresponding running of finite-size worldline coefficients. The canonical result agrees with the modified-Teukolsky calculation, while the metric-action approach reveals the radial mechanism behind the exceptional quadrupole and provides the full metric reconstruction.

gr-qc↗

arXiv2026

Geometry-induced Casimir response in a helicoidal spacetime

We investigate the Casimir response of a massive scalar field in a torsionless helicoidal spacetime with Levi-Civita connection. The background is ultrastatic and curved, with scalar curvature $R=-2\Omega^2$, and its off-diagonal metric component induces a geometric coupling between angular and axial quantum numbers. We show that individual modes exhibit a linear helicoidal splitting, whereas the linear contribution cancels in the nonchiral vacuum sum. The leading Casimir correction is therefore quadratic in the twist and defines a helicoidal vacuum susceptibility after local ultraviolet subtractions. For a cylindrical Dirichlet cavity, we compute this scheme-defined susceptibility and the associated correction to the radial Casimir force. The results identify torsionless helicoidal geometry as a controlled setting in which mode-level chirality produces a finite quadratic response of vacuum fluctuations.

hep-th↗

arXiv2026

Torsional selection rule for the spin--orbit conversion of light

Standard Pancharatnam-Berry and linear-birefringent media convert optical spin into orbital angular momentum (OAM) through an anisotropy \emph{director}, a rank-two, headless field, and therefore obey the selection rule $\Delta\ell=2q$ per unit texture charge $q$. We show that a medium with geometric \emph{torsion}, the continuum limit of a screw-dislocation array, can convert spin to OAM through the \emph{contortion} of its material connection, which enters the effective paraxial dynamics as a rank-one vector field. The resulting selection rule is $\Delta\ell=q$. Its winding is fixed by geometry and symmetry, not by a Pancharatnam--Berry director, and the process conserves the screw charge $\tilde J_z=L_z+(q/2)\sigma_z$ while exchanging $(2-q)\hbar$ of angular momentum per converted photon with the defect lattice. Paraxial simulations confirm the rule: a circular Gaussian input develops a stable, topologically quantized $\ell=+q$ vortex in the reversed helicity, with $83\%$ conversion over three Rayleigh ranges and no fine-tuning. We propose a polarization-resolved photonic-lattice discriminator in which the slope of the measured OAM versus the independently written texture charge, one for torsion, two for birefringence, separates the two mechanisms.

physics.optics↗

arXiv2026

Dirac oscillator in a helically twisted spacetime with axial torsion

We investigate the Dirac oscillator in a helically twisted spacetime endowed with a uniform axial torsion. Starting from an orthonormal coframe, we compute the Levi--Civita spin connection explicitly and separate the geometric contribution from the axial contortion. Retaining the matrix $\beta$ in the radial Moshinsky coupling, we show that the second-order problem is the ordered product $\hat\Pi_+\hat\Pi_-$ rather than the square of a single operator. The resulting radial dynamics is a coupled, self-adjoint two-component system in which the spin connection supplies the correct cylindrical radial operator, while the off-diagonal metric generates the helical combination $m/r-\omega k$ and a Coulomb-like geometric term. A finite-element solution reproduces the planar Dirac-oscillator spectrum in the flat limit and reveals asymmetric dependence on the longitudinal momentum, avoided level crossings, and a supersymmetric zero mode at $E=Mc^2$. The axial torsion and longitudinal momentum preserve this zero mode, whereas the helical twist lifts it quadratically. Sector-resolved thermodynamic functions are obtained from the relativistic bound-state spectrum. The explicit spinors further determine longitudinal vector and axial currents, and a Witten-index analysis identifies the helical twist as the deformation that removes the protected zero mode.

hep-th↗

arXiv2026

Topological control of third-harmonic generation in a mesoscopic quantum ring with spiral dislocation

We investigate the nonlinear optical response of a two-dimensional mesoscopic quantum ring subjected to a spiral dislocation, with emphasis on third-harmonic generation (THG). The topological defect is modeled through a torsion-induced deformation of space, which modifies the effective metric without introducing curvature. By combining the minimal-coupling prescription in curved space with a radial ring confinement and a perpendicular magnetic field, we derive the effective radial Schr\"odinger problem, obtain the bound states, and evaluate the nonlinear susceptibilities within the electric-dipole approximation. We show that the axial symmetry of the topologically deformed ring preserves the dipole selection rule $\Delta m=\pm 1$ and therefore suppresses second-harmonic generation, while THG remains allowed through multistep transition chains. The study is further expanded through three complementary analyses that can be implemented without changing the Hamiltonian: a dephasing-controlled study of spectral resolution, three-dimensional waterfall spectra showing the dependence on $\beta$ and $B$, and a channel-resolved decomposition of the THG amplitude. Together, these results establish the spiral dislocation as a robust geometric knob for tuning nonlinear optical activity in mesoscopic ring-shaped nanostructures.

cond-mat.mes-hall↗

arXiv2026

Geometry-Controlled Exceptional Points in Helicoidal Orbital-Angular-Momentum Photonics

Exceptional points (EPs) are non-Hermitian spectral singularities where eigenvalues and eigenvectors coalesce. We propose a geometry-controlled route to EPs in orbital-angular-momentum (OAM) photonics. In an effective torsion-free helicoidal background, the twist supplies a signed, real chiral splitting between opposite-OAM modes, while openness, gain, loss, leakage, or channel coupling, supplies the non-Hermiticity. The EP is reached when the geometric detuning compensates for a residual mode splitting and the linewidth contrast meets the non-Hermitian balance condition; the twist rate is thus the control parameter, not the source of non-Hermiticity. We obtain the OAM slope both for a confined quantum problem and, in the paraxial regime, for a helically twisted guide, and embed the OAM doublet in a multimode mode-space model to show that the EP survives spectator modes. Eigenvalue coalescence, phase-rigidity collapse, linear EP tracking with residual detuning, and branch exchange under geometric encircling provide falsifiable signatures. An OAM-resolved input-output response maps these onto spectroscopy-level observables, including spectral maps and three-dimensional Riemann-surface visualizations. A device-level paraxial simulation of two distinct photonic platforms, one reciprocal and one asymmetric-coupling Wiersig-type platform, reproduces the predicted exceptional point and its linear geometric tracking.

physics.optics↗

arXiv2026

Torsion-controlled spin transport and tunable intersubband absorption in a screw-dislocated semiconductor nanowire

We develop an effective-mass theory for spin-resolved transport and intersubband optical absorption in a finite semiconductor nanowire containing a uniform screw-dislocation-induced torsion. The central transport quantity is the band bottom of each torsion-dependent one-dimensional subband: torsion lowers this band bottom while an axial magnetic field resolves the two Zeeman branches, so that a spin-selective torsion interval opens when the Fermi level lies between the two branch minima. We distinguish this band-bottom transport threshold from the fixed-momentum transverse energy that governs the vertical intersubband optical transition, and obtain a design rule for the width of the spin-selective torsion interval that is linear in the Zeeman splitting in the small-splitting limit. Finite-size effects are incorporated by treating the active region as an open scattering region of length $L$ and radius $R$, with Fabry-Perot interference, radial boundary conditions, and surface-induced linewidth broadening. The spin-resolved response remains well defined when the effective linewidth satisfies $\Gamma_{\mathrm{eff}}\ll\Delta_Z$, a criterion quantified through polarization and conductance-contrast maps. In the optical sector, finite-radius intersubband absorption gives a torsion-tunable resonance in the THz range; surface boundary conditions shift the absolute resonance frequency and modify the oscillator strength, while, for the dominant unit-branch transition, the leading fixed-momentum torsional slope $\partial\omega/\partial\tau\simeq\hbar k_F/m^*$ is preserved. The resulting framework connects geometric torsion, spin-resolved mesoscopic transport, spin thermopower, and tunable intersubband absorption within a single open-quantum-wire model.

cond-mat.mes-hall↗

arXiv2026

Fixed-quadrupole static tidal response of Schwarzschild black holes in a cubic Weyl effective field theory

Static Love numbers of four-dimensional Schwarzschild black holes vanish in general relativity. We study how the fixed-quadrupole static tidal solution is modified by the parity-even cubic Weyl operator in the gravitational effective field theory. Working perturbatively in $\epsilon_{\rm e}=\lambda_{\rm e}(\Lambda r_s)^{-4}$, we construct the reduced quadratic radial action for static even-parity $\ell=2$ perturbations, order-reduce the higher-derivative equations, and solve the resulting boundary-value problem directly in metric variables. The order-$\epsilon_{\rm e}$ equations reduce to a first-order two-dimensional inhomogeneous system for $X_0$ and $X_K$, with $X_2$ fixed by an algebraic constraint. Horizon regularity leaves one constant, but matching to infinity shows that this freedom only renormalizes the applied tidal branch. After removing this tidal renormalization, the decaying branch is unambiguous. Calibrating the spatial sector at fixed $\ell=2$ against the associated-Legendre branches $P_2^{2}$ and $Q_2^{2}$, we obtain a fixed-quadrupole response amplitude $\Delta(B/A)=-2400\epsilon_{\rm e}$. Equivalently, the scalar fixed-$\ell$ quotient gives $\Delta k_{2,\rm sc}^{\rm fix}=-20\epsilon_{\rm e}$. The second number is a scalar fixed-$\ell$ conversion of the metric branch ratio, not, by itself, the analytically continued, gauge-invariant electric Love number. A comparison with canonical Teukolsky-based Love numbers requires an additional continuation in $\ell$ and a precise map of normalizations. The result should therefore be viewed as a reproducible metric-sector benchmark for the cubic Weyl EFT, complementary to gauge-invariant master-equation approaches.

gr-qc↗

arXiv2026

Source-driven torsional optical activity in geometrically chiral media

We develop an effective field-theoretical model for source-driven electromagnetic waves in a geometrically chiral optical medium described by a uniform axial torsion. Starting from the gauge-invariant electromagnetic field strength, we introduce a Chern--Simons-type coupling between the vector potential and the medium's axial contortion, thereby obtaining an inhomogeneous Maxwell system with prescribed external sources. For transverse cylindrical source profiles, we derive the coupled radial equations and solve them analytically for a circulating cylindrical-shell current. In the circular basis, the homogeneous problem diagonalizes, yielding torsion-split radial wavenumbers that give rise to longitudinal circular birefringence under guided-mode boundary conditions. In the weak-torsion regime, this birefringence produces a polarization rotation proportional to the propagation length and an oscillatory conversion between orthogonal linear polarizations. The source fixes the jump conditions and the relative excitation of the circular eigenmodes, thereby yielding measurable modal power and Poynting-flow signatures. A two-port scattering analysis shows that the apparent direction dependence remains Lorentz reciprocal, placing the effect in the class of reciprocal geometric optical activity rather than Faraday isolation.

physics.optics↗

arXiv2026

Shadow, acoustic redshift, and transfer observables of Lorentz-violating rotating acoustic black holes

We develop an impact-parameter-resolved transfer analysis for the rotating acoustic black hole with Lorentz symmetry violation. The background is the $(2+1)$-dimensional Lorentz-violating draining-bathtub geometry, where the draining parameter $A$ fixes the sonic horizon, the circulation parameter $B$ controls rotation, and the Lorentz-breaking parameter $\alpha$ deforms the effective acoustic metric. We derive the null-ray equations, the critical-impact-parameter conditions, the acoustic shadow interval, and the redshift transfer factor. We then formulate an intensity-transfer prescription for thin rings and extended disks that accounts for source emissivity, emitter motion, finite source width, and detector convolution. The resulting observables form a hierarchy: the shadow width probes Lorentz-violating broadening, the shadow centroid traces rotation, the left-right acoustic-redshift asymmetry tests branch-dependent Doppler and frame-dragging effects, and the integrated flux asymmetry measures their imprint on the observed intensity. We also construct synthetic two-dimensional acoustic screen maps, showing that the $(2+1)$-dimensional capture interval is naturally represented as a vertical strip whose displacement and brightness imbalance encode the combined effects of $B$ and $\alpha$. We focus on the exterior-regular regime $\alpha\geq0$, with $\alpha=0$ retained as the Lorentz-symmetric benchmark.

gr-qc↗

arXiv2026

Dark-Soliton Branch Blocking in Transonic Bose--Einstein Condensate Flows

Acoustic horizons in Bose--Einstein condensates are usually characterized through long-wavelength Bogoliubov phonons. We study a nonlinear counterpart: whether a one-dimensional dark-soliton branch can sustain upstream laboratory motion in a stationary transonic flow. The mechanism is local at leading order. A regular dark soliton has a bounded fluid-frame velocity, limited by the local sound speed; therefore, in the supersonic region, the background flow exceeds the largest upstream velocity available to the soliton branch. The sonic point is thus the upstream edge of the local dark-soliton branch, rather than a hard wall or a soliton geodesic surface. We construct stationary transonic Gross--Pitaevskii backgrounds and evolve the full order parameter in an open, nonperiodic domain. The simulations show upstream propagation on the subsonic side, finite-depth stalling on the subsonic side, and downstream advection for defects initialized in the supersonic region with upstream velocity relative to the fluid. Convergence, branch-consistency, local-density, phase-jump, and a dense scan of dimensionless upstream attempts support the soliton-like interpretation. The result is a branch-existence constraint, not a rigorous lower bound on arbitrary density minima of the Gross--Pitaevskii field.

cond-mat.quant-gas↗

arXiv2026

ModMax black hole surrounded by perfect-fluid dark matter in Lorentz-violating Kalb-Ramond gravity

We investigate a ModMax black hole surrounded by perfect-fluid dark matter within the framework of Lorentz-violating Kalb-Ramond gravity. The model combines three physically distinct contributions: nonlinear electrodynamic corrections from the ModMax sector, Lorentz-symmetry-breaking effects induced by the background Kalb-Ramond field, and environmental modifications associated with the surrounding dark matter fluid. We obtain the corresponding static and spherically symmetric black hole geometry and analyze how the charge, ModMax parameter, Kalb-Ramond coupling, and dark matter parameter affect the horizon structure and thermodynamic behavior. In particular, we study the Hawking temperature, entropy, heat capacity, and Helmholtz free energy, showing that the combined effects of nonlinear electrodynamics and Lorentz violation may shift the extremal configuration, modify the thermal stability regions, and generate nontrivial phase behavior. The perfect fluid dark matter contribution introduces an additional logarithmic correction to the geometry, becoming especially relevant at intermediate radial scales. Our results indicate that ModMax electrodynamics can effectively screen the electric sector, while the Kalb-Ramond parameter amplifies the geometric deformation and changes the thermodynamic response of the system. These features suggest that black holes in Lorentz-violating backgrounds surrounded by dark matter provide a useful arena for probing deviations from standard charged black-hole thermodynamics.

gr-qc↗

arXiv2026

Transfer observables of rotating acoustic black holes from ray tracing: shadow centroid, redshift asymmetry and flux imbalance

We construct an impact-parameter-resolved transfer framework for null acoustic rays in the rotating draining-bathtub spacetime. The formalism separates the source-independent ray geometry from the source and detector model by keeping explicit the acoustic redshift, transfer convention, emissivity, emitter velocity field, and source-to-screen mapping. The geometric capture interval provides two clean observables: a shadow centroid that shifts linearly with circulation and a shadow width that grows monotonically with circulation. Observable profiles are obtained from direct ray-source intersections, finite source width or extended-disk integration, detector convolution, and convergence checks, rather than from an approximate semi-analytic ring map. The transfer calculation shows that rotation produces a left-right redshift tilt and a branch-dependent flux imbalance, while the total flux alone remains a degenerate circulation diagnostic. The most useful diagnostics are differential quantities: the shadow centroid, branch-integrated flux asymmetry, peak asymmetry, left-right redshift asymmetry, and global redshift contrast. We also discuss how these observables respond to the transfer convention, intrinsic azimuthal emissivity, the choice of left-right split, finite resolution, and physical limitations such as dispersion, viscosity, and finite-depth corrections.

gr-qc↗

arXiv2026

Thermodynamics and emergent thermomechanical response of a quantum ring with nonminimal spin--orbit coupling

We investigate the thermodynamic and emergent thermomechanical properties of fermions confined to a one-dimensional quantum ring with effective spin--orbit interactions induced by nonminimal couplings to antisymmetric tensor fields. Using the exact spectrum obtained in the companion work, we develop canonical and grand-canonical descriptions and show that the coupling parameter~$\xi$ deforms the angular-momentum branches, reorganizing the low-energy spectrum and leaving clear signatures in the internal energy, entropy, heat capacity, and spin--orbit response functions. We also formulate an effective thermomechanical description by treating the ring circumference as a quasi-static thermodynamic variable. This leads to a pressure-like quantity and associated response coefficients, directly linked to the microscopic spectrum. In the grand-canonical ensemble, Fermi statistics strongly enhance the response, producing coupling-dependent instabilities and sign changes reminiscent of mesoscopic de~Haas--van Alphen oscillations. Finally, we introduce a phenomenological interacting extension based on an exponential resummation of the free energy, showing that collective effects can sharpen the thermomechanical response and induce anomalous thermal contraction. Our results connect spectral deformation, finite-size thermodynamics, and emergent mechanical behavior in spin--orbit-active quantum rings.

cond-mat.stat-mech↗

arXiv2026

Hawking Temperature, Sparsity and Energy Emission Rate of Regular Black Holes Supported by Primordial Dark Matter

In this paper, we investigate the thermodynamic and radiative properties of a regular black hole sourced by primordial dark matter (PDM), modeled effectively through a Dirac--Born--Infeld (DBI) scalar field. We compute the Hawking temperature, the entropy obtained from the first law at fixed PDM scale, the specific heat capacity, the sparsity parameter of the Hawking flux, and the spectral energy emission rate. Particular attention is devoted to the role played by the regularity scale parameter $α$ and to the recovery of the Schwarzschild limit. Using the normalization in which the integration constant $M$ is the ADM mass and $f(r)=1-2M/r+\mathcal{O}(r^{-3})$, we find that the PDM scale suppresses the Hawking temperature and the spectral energy emission rate relative to the Schwarzschild case. The fixed-$α$ heat capacity remains negative along the physical branch, indicating the persistence of local thermodynamic instability in the canonical ensemble. Moreover, within the effective-area prescription adopted here, the geometrical sparsity parameter receives a negative leading correction in the perturbative regime $α\ll 2M$, implying a slight reduction of the intermittency of the Hawking flux. We also distinguish between the near-horizon geometrical estimate and the shadow-based high-energy absorption cross-section used in the emission rate.

gr-qc↗

arXiv2026

Perturbations and greybody bounds of Euler-Heisenberg black holes surrounded by perfect fluid dark matter

We investigate the propagation of massless fields with spins $s=0$, $s=1$, and $s=1/2$ in the spacetime of an Euler-Heisenberg (EH) black hole surrounded by perfect fluid dark matter (PFDM). This background incorporates both the nonlinear electrodynamic correction associated with the EH effective theory and the logarithmic contribution induced by the surrounding dark matter distribution. After deriving the corresponding Schrödinger-like radial equations, we construct the effective potentials for scalar, electromagnetic, and Dirac perturbations and analyze how they are modified by the black hole charge, the EH parameter, and the PFDM parameter. The greybody factors are estimated through the rigorous Boonserm-Visser lower-bound method, and the associated partial absorption cross sections are obtained for different spin sectors using these bounds. Our results show that the nonlinear electrodynamic and dark matter parameters significantly deform the effective potential barrier, leading to potentially distinguishable changes in the transmission probabilities and absorption spectra within the model. In particular, the greybody lower bounds increase monotonically with the frequency and approach the high-frequency limit, while their low-frequency behavior is strongly affected by the geometry and by the spin of the perturbing field. Moreover, we utilize the greybody lower bound to calculate the energy emission rate. Finally, we make comparisons with the Schwarzschild, Reissner-Nordström, and pure EH limits, showing that the combined EH+PFDM background produces distinguishable corrections to black-hole scattering within the model. These results highlight greybody bounds as sensitive diagnostic probes of nonlinear electrodynamic effects and dark matter halos around compact objects.

gr-qc↗