arXiv subjects

Celio R. Muniz

Publications and source records attributed to Celio R. Muniz.

At least 19 recordsLinked to original sources

arXiv2026

Traversable Wormholes Supported by Entropy-Inspired Effective Matter Sectors

The thermodynamic interpretation of gravity suggests that modifications of horizon entropy can be encoded in effective geometries and matter distributions. Motivated by the entropy--geometry correspondence, we investigate Morris--Thorne wormholes constructed from density profiles associated with Barrow, Tsallis, Kaniadakis, logarithmic, and exponential black-hole entropies. The wormhole construction retains each entropy-induced density as input to the shape-function equation, while the radial and tangential pressures are reconstructed independently from the wormhole field equations, a barotropic radial equation of state, anisotropic conservation, and throat regularity. Barrow and Tsallis yield algebraic negative-density distributions; Kaniadakis and exponential corrections produce localized profiles; and the logarithmic sector admits both negative-density and positive-density phantom-like regimes. For every regular configuration considered, radial null energy condition violation at the throat follows from the flare-out condition. Its areal-volume integral is finite and negative for every nonzero deformation: it becomes unbounded when the regular Barrow, Tsallis, and Kaniadakis branches approach their undeformed values, but remains finite in the logarithmic and exponential limits. Removing the density deformation also fails to commute with taking the infinite-radius limit in the Barrow, Tsallis, and Kaniadakis sectors, whereas the two operations agree for the logarithmic and exponential sectors in their pole-free domains. The selected entropy-induced densities can therefore be embedded consistently in traversable-wormhole reconstructions, with the pressure sector fixed by the wormhole geometry and the global source behavior controlling both the asymptotic mass and the integrated radial exoticity.

gr-qc↗

arXiv2026

Dynamical Schwinger Production of Dipole--Antidipole Pairs in a Fractonic Lattice

We investigate field-induced excitation production from the unit-filled Mott background of a one-dimensional dipole-conserving Bose--Hubbard chain driven by a periodic quadratic potential, realizing a time-dependent rank-two electric field. Unlike protocols that manipulate pre-existing dipolar or fractonic excitations, we address their production from an initially Mott-like state without prepared dipolar or fractonic excitations. A single correlated hop directly nucleates the compact $|030\rangle$ configuration at the atomic energy $3U$, while a lower manifold derived from $2U$ contains spatially resolved dipole--antidipole configurations. Exact diagonalization shows that finite hopping turns this lower manifold into a dispersive band whose finite-chain edge lies substantially below the compact $3U$ scale. Despite this lower energetic edge, its normalized odd-harmonic spectral weight is perturbatively suppressed as $(J/U)^2$, reflecting virtual hybridization of the initial and final eigenstates. A consistent second-order treatment of the $|1111\rangle\leftrightarrow|0220\rangle$ channel includes diagonal self-energy shifts and predicts a weak-field resonance displacement confirmed by exact time evolution. Extended-chain dynamics shows genuine dipole--antidipole separation together with redistribution into higher-energy many-body sectors. The resulting mechanism provides a condensed-matter analogue of multiphoton dynamical Schwinger production in which exact dipole conservation replaces mobile opposite charges by mobile opposite dipoles, while isolated fractonic charges remain immobile.

hep-th↗

arXiv2026

Zero- and Finite-Temperature Casimir Effect in a Fracton Gauge Field

We investigate the zero- and finite-temperature Casimir interaction of the free trace-full scalar-charge fracton gauge field between two parallel reflecting boundaries. A variational analysis determines a consistent boundary-value problem that confines all five physical polarizations of the rank-two field. The spectrum separates into three faster and two slower propagating modes. At zero temperature, the vacuum interaction weights the modes by their propagation speeds; when the fast-branch speed is set equal to the speed of light, the resulting Casimir pressure is approximately 2.21 times the ideal electromagnetic value. At finite temperature, the two branches acquire different thermal weights and generate a split crossover. The normalized free energy and pressure follow distinct crossover profiles but approach the same classical high-temperature ratio of 2.5 relative to ideal electromagnetism, because the Matsubara zero mode counts the five confined polarizations independently of their propagation speeds. We derive the exact thermal interaction, its low- and high-temperature limits, and the dependence of the crossover scale on the effective gauge-field velocity. The transition from velocity-weighted quantum fluctuations to classical mode counting provides a direct spectral signature of the multi-branch structure of the higher-rank gauge field.

hep-th↗

arXiv2026

Traversable Hyperbolic Wormholes with a Casimir-Memory Source: Complexity and Shell-Free Matching

Hyperbolically symmetric wormholes provide a setting in which negative energy densities arise from the throat geometry and finite matter configurations can be matched to the hyperbolic Schwarzschild vacuum. We construct such configurations from a matter-first perspective using an effective Casimir source corrected by a gravitational-memory contribution, $ρ(r)=-α/r^4+η/r^7$. The $r^{-7}$ term is motivated by the persistent shift of the Casimir vacuum energy after a transient gravitational perturbation, while its promotion to a radial source is treated phenomenologically. The density determines the shape function, and the temporal geometry is fixed through complexity-based conditions. Full vanishing complexity, $Y_{TF}=0$, is first imposed and then relaxed through a one-parameter deformation, $Y_{TF}=(p-3)r_0/(2r^3)$. Decomposing the complexity factor into local and throat contributions shows that local vanishing complexity occurs at $p=β'(r_0)$. At this value, besides the constant-redshift solution of the finite-$r$-derivative branch, a second lapse branch is regular in radial distance. We show that pressure-free Darmois matching in the finite-$r$-derivative family requires $p<β'(r_0)$, enforcing tangential null and strong-energy-condition violations at the throat throughout the matching domain. The density remains negative in the matter-supported region, implying weak- and dominant-energy-condition violations independently of the lapse branch. The memory parameter modifies the flare-out domain, redshift profile, and matching data, while finite pressure-free junctions permit smooth matching to the hyperbolic Schwarzschild vacuum without thin shells. The construction combines a memory-corrected Casimir source with a unified complexity framework in which the temporal sectors emerge as related branches of the same radial geometry.

gr-qc↗

arXiv2026

Fermionic Casimir memory from an anisotropic gravitational pulse

We investigate the late-time energy deposited by a weak, spatially homogeneous anisotropic gravitational pulse in a massless Dirac field confined between two static parallel plates. The field satisfies MIT bag boundary conditions, while the prescribed geometry approaches Minkowski spacetime in both asymptotic time regions. Using a tetrad formulation, we show that the linear spin-connection contribution cancels for the traceless anisotropy, leaving a coupling to the shear component of the Dirac stress tensor. The pulse produces real fermion--antifermion pairs, whose deposited energy is evaluated through the corresponding Bogoliubov coefficients. Subtracting the production in unbounded space isolates a finite boundary-dependent contribution governed by the pulse duration relative to the characteristic spectral timescale set by the MIT gap. This contribution is negative in the adiabatic regime, where confinement suppresses excitations relative to the continuous free spectrum, and approaches zero from above in the impulsive limit. The resulting pressure correction is nonmonotonic and exhibits two sign changes, alternately reinforcing and reducing the ordinary attractive Casimir force. Unlike the bosonic vacuum-polarization memory previously obtained for the same class of backgrounds, the present effect is a dissipative fermionic memory carried by gravitationally created pairs. Here, memory denotes the persistent late-time modification of the quantum state after the pulse has vanished.

gr-qc↗

arXiv2026

Electrically Charged Non-Abelian Black String in Anti-de Sitter Space

We construct a new family of static, electrically charged, cylindrically symmetric black-string solutions of four-dimensional Einstein--Yang--Mills theory with a negative cosmological constant, supported by a genuinely non-Abelian $SU(2)$ vortex field. The coexistence of electric and vortex sectors renders the standard single-function Lemos metric inconsistent with the Einstein equations, requiring a three-function metric compatible with the anisotropic Yang--Mills stress tensor. Regular near-horizon and asymptotic AdS expansions provide boundary data for numerical integration of the complete field equations. Two limiting sectors are recovered: vanishing electric horizon datum yields the neutral Lemos black string with zero Yang--Mills field strength, while switching off the vortex component gives the embedded $U(1)\subset SU(2)$ charged Lemos--Zanchin solution. Perturbations about the latter show that genuinely non-Abelian hair appears at linear order through the commutator field strength, whereas its backreaction on the electric profile and geometry begins at quadratic order. The horizon equations yield the analytic local non-degeneracy bound $R_1^{\rm crit}=s_0α\sqrt{3/(4πG)}$. The asymptotic geometry exhibits a quadratic correction absorbable into an effective Abelian charge and a cubic coefficient giving the first irreducible asymptotic signature of the non-Abelian hair. The entropy obeys the Bekenstein--Hawking area law, while the temperature difference from the embedded Abelian solution arises through the asymptotic lapse normalization. The fully backreacted numerical solutions are nonlinear realizations of this transverse non-Abelian deformation.

gr-qc↗

arXiv2026

Colored Black Holes in Logarithmic Nonlinear Yang--Mills Theory

We construct static, spherically symmetric, and asymptotically flat colored black holes in four-dimensional Einstein gravity coupled to a logarithmic nonlinear Yang--Mills field with gauge group SU(2). Unlike solutions based on the Wu--Yang ansatz, the gauge sector contains a dynamical radial amplitude, and the configurations arise from a genuinely coupled nonlinear boundary-value problem. An integral identity excludes nontrivial sign-definite solutions approaching a magnetically neutral Yang--Mills vacuum, implying that colored configurations must be nodal. We numerically construct the fundamental one-node branch and verify its convergence to the ordinary Einstein--Yang--Mills colored black hole in the linear limit. Increasing the logarithmic nonlinearity lowers the ADM mass, raises the Hawking temperature, and displaces the gauge-field node toward larger radii. Branch termination is not detected over the full range of parameters investigated. Instead, the exterior geometry approaches Schwarzschild on fixed radial domains, while the colored structure develops an increasingly extended tail. Although no independent asymptotic Yang--Mills charge is present, the non-Abelian hair leaves a subleading imprint on the far-field geometry. Inside the event horizon, the representative nonlinear solutions possess no Cauchy horizon and approach a Schwarzschild-type spacelike curvature singularity, with a finite limiting mass and no oscillary mass inflation. The recovery of the linear theory is therefore nonuniform near the cetonter: solutions that are nearly linear in the exterior eventually enter the strongly logarithmic regime in the deep interior. Finally, turning points of the Hawking temperature produce divergences and sign changes in heat capacity, indicating transitions of local thermodynamic stability.

gr-qc↗

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

Gravitational Lensing in a Kasner Background: Distinguishing Wormholes and Black Holes

We investigate gravitational lensing by compact objects embedded in anisotropic Bianchi-I cosmologies using directional Jacobi maps within the thin-lens approximation. The formalism is developed for a general diagonal Bianchi-I spacetime and specialized to the Kasner solution as an analytically tractable background. Using the Ellis--Bronnikov wormhole and the Schwarzschild black hole as representative lenses, we derive anisotropic lens equations, characteristic axis-aligned lensing scales, and the corresponding critical curves. We show that the directional splitting of the characteristic scales depends on the complete source--lens--observer optical propagation and provides a geometric probe of anisotropic expansion independent of the overall lens scale. By contrast, the exact critical curves exhibit a much weaker deformation, indicating that characteristic-scale splitting and critical-curve morphology probe distinct aspects of the lens mapping. The comparison between wormhole and black-hole lenses further reveals that identical anisotropic backgrounds are filtered differently by distinct weak-field deflection laws. These results provide a simple framework for disentangling cosmological anisotropy from the local geometry of compact lenses.

gr-qc↗

arXiv2026

Traversable Casimir Wormholes with Gravitational Memory

We investigate a class of traversable wormhole geometries supported by an effective Casimir source corrected by gravitational memory. The construction is motivated by the fact that a time-dependent gravitational background can leave a permanent positive shift in the vacuum polarization of a quantum field confined to a Casimir cavity. By promoting the plate separation to an effective radial scale in the Morris-Thorne spacetime, we obtain a density profile composed of the usual negative Casimir contribution, proportional to $r^{-4}$, and a positive memory-induced correction, proportional to $r^{-7}$. The corresponding shape function is derived directly from the Einstein equations and satisfies the throat condition by construction. We determine the redshift function from a constant barotropic equation of state together with the requirement of regularity at the throat, which fixes the barotropic parameter in terms of the Casimir and memory coefficients. The flare-out condition defines the admissible range of the memory parameter and separates a Casimir-dominated sector from a phantom-like sector, with the transition point associated with a singular limit of the constant-barotropic description. We analyze the curvature scalar, the embedding structure, the energy conditions, and the Tolman-Oppenheimer-Volkoff equilibrium of the anisotropic matter source. The radial null energy condition is necessarily violated at the throat, while the tangential sector depends sensitively on the redshift gradient. We also examine the shadow radius as a phenomenological diagnostic and show that admissible solutions can overlap the EHT range for M87*. The results indicate that gravitational memory can deform Casimir-supported wormholes by softening the ordinary Casimir contribution, modifying the near-throat geometry, and reshaping the internal stress balance required to sustain traversability.

gr-qc↗

arXiv2025

LQG inspired spacetimes as solutions of the Einstein equations

Black bounces are compact objects with a wormhole structure hidden behind an event horizon. This type of metric can be obtained through general relativity by considering the presence of exotic matter. Such spacetimes can also arise within the framework of effective theories inspired by loop quantum gravity. In this work, we verify the possibility of obtaining black bounce models inspired by loop quantum gravity as solutions of general relativity. For this, we examine which sources can generate these solutions and the consequences of using these types of sources. We find that the sources can be expressed as a combination of a phantom scalar field and nonlinear electrodynamics. Once we obtain the sources in terms of fields, we analyze the energy conditions for each field separately to verify which of the fields is responsible for the violation of the energy conditions.

gr-qc↗

arXiv2025

Black holes inside cosmic voids

This study examines the gravitational and thermodynamic properties of static, spherically symmetric black holes within cosmic voids -- vast underdense regions of the universe. By deriving a novel solution based on a universal density profile for voids, we analyze its spacetime structure, which reveals two horizons: One of the black hole and the other related to the de Sitter-like behavior. As the void approaches a perfect vacuum, the black hole horizon diminishes, tending to that of the Schwarzschild solution, while the outer horizon increases. We also study the solution stability via sound speed of the fluid, as well as the thermodynamic properties, including Hawking temperature, evaporation time, entropy, and specific heat. Our results show that as the void empties, the Hawking temperature rises, shortening evaporation times. The entropy follows the area's law and specific heat exhibits a minimum for a given black hole size, indicating a thermal transition and highlighting the role of voids in the black hole evolution. These findings offer new insights into the relationship between local gravitational collapse and large-scale cosmic structure, enhancing our understanding of the black hole behavior in underdense environments. We also provide a glimpse of a potential thermodynamic interaction between the event horizon and the cosmological horizon.

gr-qc↗

arXiv2025

Quantum improved wormholes in the Dekel-Zhao dark matter halo

This work presents and investigates novel traversable wormhole solutions within the framework of Asymptotically Safe Gravity (ASG), sourced by a dark matter halo modeled by the Dekel--Zhao density profile. The scale-dependent gravitational coupling $G(k)$, derived from the ASG renormalization group flow in the infrared regime, is incorporated directly into the field equations, providing a consistent description of quantum gravitational corrections even at astrophysical scales. The combined effects of the running coupling (parameterized by $ξ$) and the dark matter characteristics determine the geometric structure and physical viability of the wormhole. The solutions satisfy the flare-out and asymptotic flatness conditions within restricted parameter domains, exhibiting enhanced curvature near the throat due to ASG corrections. Null Energy Conditions are necessarily violated at the throat, and stability analysis based on the adiabatic sound speed as well as the modified Tolman--Oppenheimer--Volkoff equation reveal that quantum effects from ASG counteract the destabilizing influence of dark matter. Phenomenologically, the wormhole shadow radius increases nearly linearly with $ξ$, lying within the Event Horizon Telescope bounds for Sgr~A$^*$ when $ξ/M \simeq 0.8--0.9$, thus suggesting that ASG-corrected wormholes may represent observable signatures of quantum gravity in the strong-field regime.

gr-qc↗

arXiv2025

Traversable Wormholes Sourced by Dark Matter in Loop Quantum Cosmology

In this work, we investigate the existence of wormholes within the framework of Loop Quantum Cosmology, using isotropic dark matter as the source. We analyze three distinct density profiles and solve the modified gravity field equations alongside the stress-energy tensor conservation, applying appropriate boundary conditions to obtain traversable wormhole solutions. Each solution is shown to satisfy the geometric criteria for wormholes, and their regularity is verified by computing the Kretschmann scalar to ensure the absence of singularities under determined conditions. Additionally, we examine the stress-energy tensor to identify scenarios in which energy conditions are violated within this model. The wormhole geometry is further explored through embedding diagrams, and the amount of exotic matter required to sustain these structures is computed using the Volume Integral Quantifier. Finally, we study the shadow produced by our wormhole solution, considering one of the dark matter density profiles, and compare it with observations of the M87 galaxy.

gr-qc↗

arXiv2025

Field Sources for Wormholes With Multiple Throats/Anti-throats

In this work, we investigate wormhole geometries with multiple throats and anti-throats in general relativity. The existence of these structures is identified through the analysis of minima and maxima in the area of the solution. Using embedding diagrams, we visualize the geometry and demonstrate that these objects exhibit a complex structure, distinct from standard single-throat wormholes. We further analyze the geodesic motion in such spacetimes. The solutions are derived from Einstein's equations by coupling a phantom scalar field to nonlinear electrodynamics, and we show that distinct scalar field profiles can generate the same spacetime geometry. Additionally, we examine the energy conditions and demonstrate that, for specific parameter choices, all energy conditions can be partially satisfied in certain regions of spacetime.

gr-qc↗

arXiv2024

Casimir Wormholes with GUP Correction in the Loop Quantum Cosmology

In this paper, we obtain novel traversable, static, and spherically symmetric wormhole solutions, derived from the effective energy density and isotropic pressure resulting from the Casimir effect, corrected by the Generalized Uncertainty Principle (GUP) within the framework of Loop Quantum Cosmology (LQC). The goal is to explore the interplay between competing quantum gravity effects and quantum vacuum phenomena in the emergence of non-trivial spacetime structures. We examine features such as traversability, embedding diagrams, energy conditions, curvature, and stability of the obtained solutions. Additionally, we analyze the junction conditions required to integrate the wormhole spacetime with an external Schwarzschild spacetime and calculate the amount of exotic matter needed to maintain the wormhole. Finally, we evaluate the conditions under which this latter remains visible or is hidden by the event horizon associated with the Schwarzschild spacetime.

gr-qc↗

arXiv2024

Traversable Wormholes from Loop Quantum Gravity

This study introduces and investigates Lorentzian traversable wormhole solutions rooted in Loop Quantum Gravity (LQG). The static and spherically symmetric solutions to be examined stem from the energy density sourcing self-dual regular black holes discovered by L. Modesto, relying on the parameters associated with LQG, which account for the quantum nature of spacetime. We specifically focus on macroscopic wormholes characterized by small values of these parameters. Our analysis encompasses zero-tidal solutions and those with non-constant redshift functions, exploring immersion diagrams, curvatures, energy conditions, equilibrium requirements, and the requisite quantity of exotic matter to sustain these wormholes. The investigation underscores the influence of LQG parameters on these features, highlighting the pivotal role of spacetime's quantum properties in shaping these wormholes and governing their behavior.

gr-qc↗

arXiv2023

Black strings from dark matter

In this paper, we obtain two different static black string solutions by considering as sources axisymmetric dark matter distributions in 3+1 dimensions. These solutions tend asymptotically to the usual static and uncharged black string vacuum solution predicted by General Relativity (GR). We show that both the solutions present an event horizon each, like the vacuum solution, which is larger than the horizon of the latter. Then, we obtain the Hawking temperature associated with the black string solutions. Differently from what occurs with the static black string in the vacuum, we find that there exists a linear density of mass (or tension) remnant associated with a vanishing Hawking temperature for the obtained solutions. Thus, we analyze how the presence of dark matter affects the occurrence of the remnants. Further, we calculate other thermodynamic quantities, namely entropy, heat capacity, and free energy per length unit, showing that thermal phase transitions can occur in the presence of dark matter. We also analyze the weak (and null) energy conditions and conclude that the dark matter does not behave like an exotic fluid. Finally, we obtain the corresponding stationary solutions, determining their tensions as functions of both the mass and angular momentum of the black strings.

gr-qc↗