arXiv subjects

Edson Otoniel

Publications and source records attributed to Edson Otoniel.

At least 19 recordsLinked to original sources

arXiv2026

Regularization effects on the observational appearance of asymmetric thin-shell wormholes from a new string-cloud geometry

We investigate how rational regularization of the new Letelier--Alencar string-cloud geometry changes the optical appearance of reflection-asymmetric thin-shell wormholes. We compare junctions with two nonregular exteriors, a regular observer exterior paired with a nonregular one, or two regular exteriors at fixed leading asymptotic masses, throat radius, string strength and regulator fractions. Critical scales, ray classes, orbit numbers and transfer functions are combined with three emission profiles and matched black-hole controls. Face-on and inclined images use the same prescribed emitter motion: circular timelike geodesics outside the innermost stable circular orbit and an inward plunge conserving its specific energy and angular momentum inside. Although the core is excised, regularization changes the retained exterior and throat matching. For the sampled parameters, the observer critical screen impact decreases from $10.392μ_1$ to $9.642μ_1$, where $μ_1$ is the observer-side asymptotic mass scale. Regularizing the second exterior then contracts the reflected interval from $3.890μ_1$ to $1.248μ_1$ without changing ordinary observer-side rays. Returned brightness depends on source support and velocity-dependent frequency shifts: the regular--regular image nearly coincides with its black-hole control for the outer-edge emission model face-on, while inner emission reveals returned structures. At large sampled inclination that near-degeneracy can be lifted. This separates regularization-dependent propagation from the emission and viewing conditions that determine its image contrast.

gr-qc↗

arXiv2026

Hyperbolic scaling of the small-exponent limit in magnetic nonlinear electrodynamics

A magnetic spacetime can approach Schwarzschild while its electromagnetic characteristics remain singular in the same parameter limit. We study this separation in fractional-power nonlinear electrodynamics as the exponent tends to zero with asymptotic mass, magnetic charge and nonlinear coupling independently fixed. The extraordinary polarization admits a common physical time direction only outside a boundary that grows as the inverse fourth root of the exponent. On this radial scale, the lapse tends to unity but the constitutive angular response retains a nondegenerate barrier and finite scaled critical data. An exact representation of the exterior electromagnetic energy yields complete second-order corrections to the orbit and impact, separating mass and charge contributions and their distinct cancellations. Constraining the mass to equal the electromagnetic self-energy preserves the leading critical constants while changing the approach from fourth-root to square-root corrections. Returning rays remain inside the admissible exterior and define a limiting scattering function with a calculated logarithmic strong-deflection coefficient. In the weak regime, constitutive bending decays as the inverse fourth power of scaled impact, whereas finite mass supplies a slower inverse-impact tail. We determine their competition scale, its accessibility above the critical impact, and the accuracy of the two-term approximation. Independent energy, orbit and scattering calculations check the expansions and resolve their parameter-dependent convergence. The analysis shows how a nearly vacuum background can support a distinct exterior optical limit through the nonlinear constitutive response.

gr-qc↗

arXiv2026

Slowly rotating white dwarfs in f (R, T ) = R + 2λT gravity: structure and stationary tidal response

We calculate the structure and stationary tidal response of cold carbon fluid white dwarfs in $f(R,T)=R+2λT$ gravity through second order in uniform rotation. Equilibria are compared at fixed baryon number, with angular momentum also conserved during each aligned electric quadrupolar tidal perturbation. Negative coupling increases radii and dimensional tidal deformabilities over the common mass range. For the baryon sequence studied, background readjustment accounts for 95.8--97.5\% of the rotational enhancement at 40\% of each model's Kepler reference frequency. The explicit mixed rotational tidal contribution is positive and numerically resolved, but subdominant. At that spin, the enhancement relative to each coupling's static model decreases from 107.4\% in general relativity to 14.2\% at the most negative coupling, despite its larger absolute deformability. This reduction reflects less relative background expansion and a different Love-number variation.

astro-ph.SR↗

arXiv2026

Thin-shell wormholes from magnetic black holes in exponential electrodynamics

Transparent magnetic wormholes can share a black hole exterior while their supporting matter controls the response of the throat. We construct symmetric thin shells from the magnetic black hole of exponential nonlinear electrodynamics and derive their equilibrium stresses and linear radial stability criterion. Restricting the seed to its zero-bare-mass magnetic branch ties the charge and coupling along the fixed-mass family. In sampled cases, calibrated linear barotropic shells are unstable, whereas variable phantom and variable Chaplygin laws admit locally stable radial sectors. Explicit radius dependence strengthens the phantom restoring term; the Chaplygin response cancels the divergent inverse lapse contribution and permits stable sectors close to a non-extremal seed horizon. The surface density remains negative, although an inner interval satisfies the tangential null and intrinsic strong energy conditions. At the seed photon sphere, the two variable laws share an exact stabilization threshold. The complete radial averaged null energy remains negative even when the proper shell energy tends to zero. Numerical null geodesic imaging uses independent, minimally coupled light and transparent junctions, with celestial sources and rotating thin disks truncated at the innermost stable circular orbit (ISCO). For observer-side disk emission with the prescribed ISCO truncation and a throat below the seed photon sphere, inclined images coincide with the seed black hole image. A throat above that sphere removes selected returning contributions while preserving much of the bright primary structure. Illuminating the opposite exterior adds inner disk arcs, but a central dark region can survive because the disk does not illuminate every transmitted direction. Image degeneracy depends jointly on the retained null trajectories and the emitting support, rather than on the presence of a horizon alone.

gr-qc↗

arXiv2026

Strong-deflection scaling in nearly symmetric thin-shell wormholes

The angular winding of a returning light ray can grow while the family of admissible impacts disappears. We characterize this competition near reflection symmetry in a static thin-shell wormhole joining Schwarzschild exteriors of slightly different masses. Exact shell-frame matching fixes the reflected interval, and a normal coordinate at each nondegenerate photon-sphere maximum gives a composite angular expansion with controlled error on compact interior channel intervals. The result remains valid when the throat distance divided by the mass contrast tends to zero, stays finite or diverges. For a throat distance proportional to a positive power of the fractional mass difference, the width exponent increases from one toward two and then saturates, while the logarithmic winding coefficient decreases from three toward two. Fixed-throat configurations retain their finite-distance amplitude and coefficient three. Reference-subtracted profiles connect the intermediate sector to finite and vanishing scaled throat positions. Independent quadratures test the scaling laws and resolve the slower convergence associated with changing scale ratios. The shrinking solid-angle aperture follows directly from the critical-impact gap. For an axial observer and a transparent test disk confined to the same exterior, the return-phase condition selects the admitted intersections; sampled near-symmetric configurations shift the first available global crossing to a later label. The closing aperture and increasing winding are therefore linked by the accessible radial extent, with disk access determined by the phase accumulated on the emitting segment.

gr-qc↗

arXiv2026

Thin-Shell Wormholes in Born--Infeld-Type Magnetic Spacetimes

We investigate the radial stability, thermodynamic balance, and bilateral disk images of symmetric thin-shell wormholes built from Born--Infeld-type magnetic exteriors. The exact lapse and junction conditions define a fixed-mass family in which magnetic self-energy ties the nonlinear scale to the charge. The shell has negative energy density, although an inner sampled region satisfies the tangential null and intrinsic strong energy conditions. Linear radial perturbations yield unstable calibrated barotropic samples and stable sectors for the generalized and modified cosmic Chaplygin laws on selected real branches. Analytic horizon and large-radius limits explain the stability transitions and show how the modified linear pressure term can replace outer stability with finite radial intervals. Minimally coupled Maxwell rays traverse transparent junctions between exteriors with a common arctangent emission profile, viewed by a static observer. The wormhole-black-hole intensity difference separates transmitted disk light from emission removed by throat excision. Compared with static emitters, circular and plunging motion reduce the face-on intensities in the studied cases; inclined motion generates strong azimuthal contrast. Increasing the subcritical charge contracts the critical circle and permits more disk crossings near it in the optical samples. Under a reversible first law, flux cancellation gives isentropic motion at positive temperature, with entropy dependence left to a constitutive completion. These results distinguish geometric, material, and kinematic effects on shell support and disk illumination.

gr-qc↗

arXiv2026

Magnetic pressure anisotropy in ultra-dense white dwarfs: Landau quantization and neutronization effects

Strong magnetic fields modify the thermodynamics of white dwarf (WD) matter by quantizing the transverse motion of degenerate electrons into Landau levels and splitting the pressure into components parallel and perpendicular to the magnetic field. We investigate how this microscopic pressure anisotropy affects ultra-dense WD sequences when Coulomb lattice contributions, electron capture thresholds, neutron drip limits, and nuclear composition are treated consistently in the equation of state (EoS). The stellar equilibrium structure is obtained by solving an anisotropic extension of the Tolman--Oppenheimer--Volkoff (TOV) equations, where $P_r = P_\parallel$ and $P_t = P_\perp$ denote the radial and tangential pressures, respectively. We compare the post-electron-capture branches with their corresponding pre-capture sequences for pure $^{12}\rm{C}$, $^{16}\rm{O}$, $^{20}\rm{Ne}$, and $^{24}\rm{Mg}$ compositions, as well as for fixed 50/50 C/O, Ne/O, and Mg/Ne mixtures. The EoS predicts $P_\perp < P_\parallel$ in density ranges where only a few Landau levels are occupied. Consequently, pressure anisotropy shifts the stellar sequences toward smaller radii, with only minor changes in the maximum masses. We also find that post-capture configurations cannot be interpreted from the mass--radius plane alone, since the corresponding $M(ρ_c)$ curves reveal unstable portions after the maximum mass is reached. Our results show that strong magnetic fields significantly reduce the radii of low-mass WDs, yielding better agreement with the observational data available in the Montreal White Dwarf Database and suggesting that future high-precision observations of massive magnetic WDs could help assess the role of magnetic pressure anisotropy in determining their masses and radii.

astro-ph.SR↗

arXiv2026

Scalar Casimir Effect from Bilocal Correlations in a Wormhole Foam

We determine how spatially bilocal correlations induced by a dilute ensemble of virtual Euclidean wormholes modify the scalar Casimir interaction between parallel Dirichlet plates. From the leading monopole action, we isolate an equal-Euclidean-time sector and construct a point-throat, first-order matched spectator model with fixed foam statistics. Global two-plate inclusion-exclusion over all mouth-pair center positions yields a continuous fixed-separation kernel free of the logarithmic image structures produced by a restricted translation sector. The kernel is quadratically suppressed at coincidence, changes sign near 0.695 plate spacings, and tends to a positive large-separation plateau. Averaging over truncated-Gaussian, log-normal, and Gamma distributions with a common relative width yields closely spaced energy curves but a finite shape dependence. Differentiating the dimensional energy at fixed ensemble parameters gives a leading-order pressure threshold of 0.05 in the large-separation limit. In the truncated-Gaussian scan extending to twelve plate spacings, an amplitude of 0.06 yields a crossover near a separation ratio of 3.17, whereas amplitudes of 0.02 and 0.04 remain attractive and 0.05 is critical. The scalar cavity therefore provides a scale-selective probe of spatial bilocality whose leading boundary response can change sign within the declared model.

hep-th↗

arXiv2026

Fermi Acceleration Mechanisms Beyond Lorentz Symmetry

We construct models for first- and second-order Fermi acceleration of particles, incorporating generic frame transformations, dispersion relations, and conservation laws. Within this framework, we study deformations of Lorentz symmetry via the $κ$-Poincaré algebra in the bicrossproduct and classical bases, which respectively deform and preserve the relativistic dispersion relation. We also examine explicit Lorentz symmetry violation and compare the results with deformed relativity and special relativity. The energy spectra present different shapes when one considers deformation or violation of Lorentz symmetry in superluminal or subluminal scenarios. One of the possible outcomes is an intense decay of the spectrum for higher energies. We also gather the predictions of all the scenarios considered, comparing the spectra produced at the source in the energy domain, which is the variable in which cosmic ray observatories report their measurements.

gr-qc↗

arXiv2026

Optical effects of one-sided Kiselev-type quintessence in reflection-asymmetric polymer thin-shell wormholes

Strong-field rays that traverse a wormhole can carry optical information about an exterior inaccessible to the observer. We investigate this mechanism in a reflection-asymmetric thin-shell wormhole formed by joining a pure-polymer exterior containing the observer and emitting disk to a polymer geometry with a Kiselev-type anisotropic environment on the opposite side. Equal masses and a common polymer scale, angular geometry, and throat position isolate the effect of one-sided quintessence. We derive the shell-frame optical matching and calculate matched critical scales, null-ray topologies, orbit numbers, transfer functions, and face-on intensity maps for three emission prescriptions. The matching projects the opposite-side photon barrier onto a distinct inner edge of the observer screen, while the outer cosmological-type horizon partitions cross-throat rays into returned and terminal families. Across the admissible parameter grid, increasing the environmental amplitude widens the returned screen interval, increasing the polymer correction contracts it, and changing the environmental exponent produces competing trends. Observer-side orbit numbers and ordinary transfer branches remain invariant under changes confined beyond the throat, providing an exact control, whereas returned branches move and broaden. Once these branches enter the emitting support, they generate additional inner annuli at source-dependent onset strengths. The combined geometric and radiative analysis identifies a controlled cross-throat optical response to one-sided quintessence and shows how environmental information beyond the throat is encoded in matched critical structure and image morphology.

gr-qc↗

arXiv2026

Teleparallel torsion and white dwarf structure in $f(T)=T+ΞT^2$ gravity

We investigate how quadratic torsion modifies the equilibrium structure of white dwarfs in covariant $f(T)=T+ΞT^2$ gravity. Static spherical configurations are calculated with a fixed equation of state for cold carbon matter, including relativistic electron degeneracy and Coulomb lattice corrections. The stellar interior is matched to a vacuum exterior, and the mass is determined from the asymptotic geometry. At fixed central density, negative couplings produce more massive and more compact configurations than general relativity, whereas positive couplings give smaller masses and larger radii. The deviations increase with central density and are more pronounced in mass than in radius. The first limiting feature of each sequence depends on the coupling. For $Ξ=-10^{18}\,\mathrm{cm}^{2}$, the sequence remains monotonic up to the electron capture density and reaches $1.508\,M_\odot$. General relativity and $Ξ=+10^{18}\,\mathrm{cm}^{2}$ instead reach mass turning points at $1.385\,M_\odot$ and $1.366\,M_\odot$, respectively. The positive extreme can be continued as an equilibrium solution to the capture density, where its mass decreases to $1.24\,M_\odot$, but this configuration lies beyond the turning point and is not the maximum mass along that sequence. These results identify a density dependent structural response to torsion that changes the stellar mass scale without modifying the matter equation of state.

astro-ph.SR↗

arXiv2026

Symmetric Thin-Shell Wormholes from a Regularized String-Cloud Black Hole: Energy Conditions, Multi-Fluid Stability, and Optical Signatures

We construct a symmetric thin-shell wormhole from two copies of the positive-lapse exterior of a rationally regularized Letelier--Alencar string-cloud black hole with a finite-curvature anti--de Sitter core and string-cloud asymptotics. Using the Darmois--Israel formalism, we derive the surface stresses, energy-condition combinations, conservation law, and effective potential. Every admissible static throat has negative surface energy density, so the weak and dominant energy conditions are violated, whereas the null condition restricted to directions tangent to the shell, and consequently the intrinsic strong condition, holds only in the inner sampled exterior. The radial-vacuum relation of the bulk source removes the external momentum flux. We derive a general local-stability criterion for density- and radius-dependent equations of state and apply it to five surface-fluid models, calibrating one parameter at each static throat. Across the sampled families, barotropic shells remain unstable, whereas the other closures can admit parameter-dependent stable branches. An exact unregularized control shows that the energy-condition structure and the radial-stability signs of the first three closures persist without the rational regulator, whereas the cosmic-Chaplygin stability sign can change while the selected calibration branch remains real and simple. Backward ray tracing shows that throat location primarily reorganizes higher-order and through-throat images, while string-cloud strength and inclination control annular structure and Doppler asymmetry. Comparisons of one- and two-sided source configurations isolate genuine far-side images and show that the central dark region depends on the source distribution.

gr-qc↗

arXiv2026

Thin-shell wormholes in cosmic voids

Cosmic voids are underdense regions that can provide an effective large-scale environment with a de Sitter-like gravitational behavior. Motivated by recent black-hole solutions embedded in void density profiles, we construct a symmetric thin-shell wormhole by gluing two copies of the positive-lapse region of a black hole inside a cosmic void. The surface stresses are obtained from the Darmois--Israel junction conditions, and the corresponding null, weak, dominant, and strong energy-condition combinations are written directly in terms of the void mass function and density profile. We further develop the thermodynamics of the static shell, deriving a first law that relates the shell entropy to the black-hole and cosmological-like horizon entropies. We then formulate the radial dynamics of the throat through an effective potential and study the local stability of static configurations when the exotic matter on the shell obeys either a generalized cosmic Chaplygin gas or a modified cosmic Chaplygin gas equation of state. In both models the Chaplygin parameter $B$ is fixed by the static junction condition, so that the remaining stability test is governed by the void geometry and by the equation-of-state parameters. Numerical results reveal that GCCG-supported configurations are generically unstable, whereas MCCG-supported wormholes can be stable for a sufficiently large linear term in the equation of state. The resulting framework connects the de Sitter-like structure of cosmic voids with the standard thin-shell wormhole formalism and provides a starting point for identifying stable or unstable wormhole configurations located between the black-hole and cosmological-like horizons of the void spacetime.

gr-qc↗

arXiv2026

Bayesian constraints on quadratic $f(Q)$ gravity from the ADM mass of white dwarfs

We calculate static equilibrium sequences for white dwarfs (WDs) in quadratic symmetric teleparallel gravity, f(Q)=Q+alpha Q^2, and perform a Bayesian comparison between the negative-coupling sector, general relativity (GR), and the positive-coupling sector using mass-radius measurements. Regular interior solutions are obtained by imposing the affine field equation and selecting the analytic branch C=r exp(B/2), and are matched to asymptotically flat exterior spacetimes to determine the ADM mass. The matter sector is described by a cold carbon-12 equation of state including relativistic electron degeneracy, nuclear rest energy, and Coulomb lattice corrections. Central density is marginalized at fixed alpha with a log-uniform prior. The sequences span 10^14 <= |alpha|/cm^2 <= 10^21. Positive couplings shift the compact branch toward larger radii and lower masses, whereas negative couplings produce high-mass extensions, including an admissible equilibrium configuration with M_ADM=14.34 solar masses. Using Sirius B, QS Vir, V471 Tau B, ZTF J1901+1458, and LHS 4033, we obtain conditional posterior medians alpha_-= -1.12x10^16 cm^2 and alpha_+=1.85x10^17 cm^2. With equal prior weights, the posterior probabilities for the negative, GR, and positive sectors are 0.228, 0.378, and 0.395, respectively, with ln(B_+/GR)=0.043. Current data therefore provide conditional constraints on the coupling but no direct evidence for modified gravity, emphasizing that the ADM mass prescription and admissible stellar domain must be consistently defined when using WD observations to constrain the theory.

gr-qc↗

arXiv2026

Modified electron dispersion relations in degenerate white dwarfs

We investigate how modified electron dispersion relations affect the structure of cold white dwarfs (WDs). The deformation is introduced only in the degenerate electron equation of state, through the energy of a single particle and the group velocity, while the stellar mass density remains dominated by ions through the relation $ρ\simeq μ_e m_u n_e$ imposed by charge neutrality. The resulting equations of state are coupled to the standard TOV equations, with no modification of the gravitational field equations. For a baseline composed of carbon and oxygen with $μ_e=2$, the undeformed limit recovers a maximum mass in the Chandrasekhar scale, validating the normalization of the calculation before the modified cases are considered. The first model of modified dispersion produces only a modest stiffening over the parameter range studied, whereas the logarithmic model depends strongly on the sign of the deformation parameter: negative values increase the pressure and the maximum mass, while positive values soften the sequence. These results show that WDs can isolate the impact of modified electron kinematics on compact star structure, but the logarithmic branch in particular requires further restrictions from its physical domain, stability conditions, and observational constraints on mass and radius.

astro-ph.SR↗

arXiv2026

White Dwarf Stellar Structure from Effective Polymer Geometry in Loop Quantum Gravity

We construct an effective Tolman Oppenheimer Volkoff system for cold carbon white dwarfs using the areal radius form of a polymer metric sector motivated by loop quantum gravity. The two asymptotic mass parameters of the geometry are retained in the stellar prescription through $M_B\rightarrow m(R)$ and $M_W=ηm(R)$, while the polymer amplitude is controlled by $A_λ$. The matter sector is kept fixed and is described by the Chandrasekhar equation of state and by the same carbon model with the Coulomb lattice correction. The resulting equations recover the general relativistic TOV system and the symmetric polymer limit. For the undeformed sequences we obtain $M_{\max}=1.4166\,M_\odot$ for the Chandrasekhar model and $M_{\max}=1.3850\,M_\odot$ when the lattice correction is included. Turning on $A_λ$ shifts the massive part of the equilibrium sequence upward without stiffening the equation of state, reaching $M_{\max}=1.7125\,M_\odot$ and $1.6907\,M_\odot$ at $A_λ=100$ for the two matter models. These configurations remain within the matter domain imposed by the inverse beta decay boundary used in the scan. The asymmetric ratio $η=M_W/M_B$ changes the metric function near the polymer transition region, but its effect on white dwarf observables is small: across the selected configurations, $M_{\max}$ changes by less than $0.1\%$ and the corresponding radius by less than $0.33\%$. The calculation therefore identifies $A_λ$ as the parameter controlling the super Chandrasekhar displacement of the mass radius relation, while $η$ acts mainly as a geometric asymmetry parameter in the low compactness regime probed by white dwarfs.

astro-ph.SR↗

arXiv2026

Junction Conditions, Radial Stability, Thermodynamics, Optical Geometry and Appearance of Polymer-Quintessence Thin-Shell Wormholes

Thin-shell wormholes built from effective black hole geometries are sensitive not only to the lapse function but also to the choice of areal radius. We construct a reflection-symmetric thin-shell wormhole from the positive-lapse sector of a polymer black hole surrounded by Kiselev-type quintessence and keep the nonareal angular function throughout the junction, stability, thermodynamic, and optical analyses. The Israel junction conditions give a negative surface energy density for every static throat on the positive branch, while the tangential null and intrinsic strong energy combinations are controlled by the local lapse slope. The radial dynamics is written as an effective-potential problem in which the nonareal sector produces a momentum-flux term and modifies the local stability criterion for surface equations of state with explicit radius dependence. For the sampled calibrated configurations, the linear barotropic and variable phantomlike closures remain locally unstable, whereas the variable Chaplygin gas admits finite linear radial stability windows. The same geometric correction also modifies the local first-law balance and shell entropy bookkeeping, while the optical analysis shows that cross-throat propagation generates additional inner image branches despite the wormhole and black hole geometries sharing the same exterior critical curve. These results identify how polymer corrections and a quintessence environment jointly reorganize the matter content, radial response, thermodynamic bookkeeping, and optical appearance of the resulting thin-shell wormhole.

gr-qc↗

arXiv2026

Localized magnetic pressure anisotropy in strange dwarfs with crystalline crusts

We study equilibrium sequences of magnetized strange dwarfs composed of a self bound MIT bag strange matter core, with $B_{\rm bag}^{1/4}=145\,{\rm MeV}$, and an ordinary crystalline crust. The aim is to determine how nuclear composition changes and magnetic pressure anisotropy in the crust modify the mass radius relation. The strange core is kept isotropic, while the crust is described either by pure nuclei stopped at the first inverse beta threshold or by electron capture sequences extended to neutron drip for C, O, Ne, and Mg compositions; selected mixed crusts are also considered up to the first instability. The stellar structure is solved with the radial pressure as the integrated pressure and with the anisotropic contribution $2(P_t-P_r)/r$ restricted to the crust. This treatment is compared with ordinary white dwarf sequences and with scalar pressure branch calculations. We find that extending the crust to neutron drip produces more compact strange dwarf branches than stopping at the inverse beta threshold, because the evolved crust is softer and the core crust transition occurs at higher pressure. Magnetic anisotropy further shifts the selected branches toward smaller radii, with the effect visible across the compositions studied and clearer at fixed stellar mass. The comparison with compact objects from the Montreal White Dwarf Database is used only as an observational reference plane, but it indicates that compact white dwarf candidates are a relevant region for testing small core strange dwarf scenarios.

astro-ph.SR↗