This study investigates an Einstein-nonlinear electrodynamic black hole generated by a Yukawa-screened electromagnetic potential and examines its thermal properties through the calculation of the fundamental thermodynamic potentials and variables. The effect of thermal fluctuations on the calculated standard thermodynamic quantities is analyzed through two different correction terms added to the Bekenstein-Hawking entropy. In this work, the thermodynamic behavior in cases where the black hole has a relatively large event horizon is investigated using a logarithmic correction term representing corrections arising from quantum fields in constant backgrounds. In addition, thermal fluctuations occurring in cases where the event horizon is small are analyzed through an exponential correction term added to the entropy, reflecting non-perturbative quantum effects. Finally, the thermodynamic functions for all obtained cases are examined graphically, and the stability properties of the black hole are discussed in detail.
In this study, we apply the Gibbons–Werner approach based on the Gauss–Bonnet theorem to examine the particle deflection in both non-plasma and plasma mediums as well as shadow formation of a black hole in the dark-energy field. The Gibbons–Werner method geometrically interprets the particle trajectory in terms of the curvature of optical space and the particle deflection in the weak-field limit and investigates the strong angle in spacetime into the context of relativistic spacetime. Using a ray-tracing analysis, we also study the influence of plasma on photon orbits, the shadow radius, and the emission energy. We study black hole geometry and non-magnetized plasma, significantly altering the shadow radius. These results extend the modified spacetime and provide theoretical insight relevant to current Event Horizon Telescope observations.
A screw dislocation in a face-centred cubic Cosserat lattice, treated as a classical elastic system, produces a dimensionless tunnelling amplitude TPN−1=137.035999177. The elastic moduli follow from Born–Huang homogenisation of the discrete lattice. The single remaining parameter, the Cosserat coupling number N2, is fixed at 1/π by the rolling-contact condition for tangent spheres and confirmed variationally.The amplitude generates a convergent perturbation series whose every coefficient is determined by FCC geometry: a topological integer from the Cosserat skyrmion winding, the rank-1 self-energy of the coupled translational and rotational sectors, and inter-valley scattering on the close-packed plane. The lattice spacing cancels and no parameter is adjustable.The FCC lattice carries two independent elastic modes. A single node tunnels through the Peierls–Nabarro barrier in the shear channel; the 19-node Born stability cluster tunnels cooperatively in the compression channel, with amplitude TPN19. Shear is topological and the output is dimensionless. Compression changes bond lengths, and extracting a coupling constant requires one further input: a length scale.The defect-gauge dictionary of Kröner, Kleinert, and Katanaev–Volovich identifies the tunnelling amplitude as the coupling constant of the effective gauge theory. The shear-channel output is numerically indistinguishable from the inverse fine-structure constant, α−1=137.035999177(21). The electromagnetic character of the shear channel motivates the classical electron radius re as the lattice spacing. With that identification, the compression channel coincides with Newton’s gravitational constant within its 22 ppm experimental uncertainty. Whether these coincidences reflect deeper structure or are accidental, the relationship warrants further investigation.
We study topological kink solutions in a non-canonical ϕ4 field theory in two-dimensional spacetime, where the kinetic sector is deformed by a hyperbolic field-dependent function that softly breaks the Z2 symmetry while preserving the topological sector and the Bogomol’ny–Prasad–Sommerfield (BPS) structure. The model is motivated by its connection to ferroelectric materials and crystalline lattice descriptions. Although the kinetic function is singular at ϕ=0, we demonstrate analytically that this singularity is dynamically regularized along the BPS orbit, leaving all physical observables finite. By varying the deformation and asymmetry parameters, standard kink solutions undergo a continuous transition into symmetric and asymmetric double-kink configurations with internal layered structure, while all solutions saturate the same BPS energy bound. A detailed linear stability analysis reveals that the effective Schrödinger-like potential reorganizes from a single-well into multi-well profiles in direct correspondence with the internal structure of the defects. The translational zero mode persists throughout but acquires a nontrivial spatial profile – developing symmetric or asymmetric localization depending on the asymmetry parameter – providing a direct diagnostic of the internal geometry of the defect. These results establish smooth kinetic deformation as a systematic and controllable mechanism for engineering internal structure in topological defects, complementary to and independent of potential-based approaches.
We propose to define entanglement in terms of local unitary transformations acting on some parts of a system that can be undone by local unitary transformations acting on other parts. This leads to a characterization of entanglement in terms of groups. We refer to these as entanglement groups, and we refer to this notion as g-entanglement. We discuss the physical meaning of entanglement groups and contrast g-entanglement with other, more conventional definitions of entanglement. For pure states, entanglement groups are constructed as certain quotients of the stabilizer group and its subgroups. For mixed states, entanglement groups can be constructed from stabilizers of the purification. We analyze the structure of entanglement groups, show that they have properties which correspond to monogamy of entanglement, and explore the restrictions placed by separability. We show that g-entanglement underlies several well-known quantum tasks.
Fluctuation-induced forces in systems undergoing second-order phase transitions depend on the ensemble in which they are defined We present exact results and compare the behavior of two such forces: the critical Casimir force in the grand canonical (fixed external field h) ensemble and the critical Helmholtz force in the canonical (fixed average value of the order parameter m) ensemble. Since these forces also depend on the boundary conditions, we clarify this dependence by studying Dirichlet–Dirichlet, Neumann–Dirichlet, Neumann–Neumann, and periodic boundary conditions on the case of the three-dimensional Gaussian model. We find that for Dirichlet–Dirichlet and Neumann–Dirichlet boundary conditions the Casimir and the Helmholtz forces differ from each other. For Dirichlet–Dirichlet boundary conditions, the Casimir force is always attractive, while the Helmholtz force can be both attractive and repulsive as a function of T and m. For Neumann–Dirichlet boundary conditions, the Casimir force changes sign from repulsive to attractive with the increase of h, while the Helmholtz force stays always repulsive. Under periodic and Neumann–Neumann boundary conditions, the Casimir force and the Helmholtz force coincide; they are always attractive.
A new spin-current model of electric polarization of spin origin is developed for magnetic structures with an anisotropic gyromagnetic-ratio tensor (g-factor). Three mechanisms of the magnetoelectric effect are proposed, arising from the symmetric Heisenberg exchange interaction, the Dzyaloshinskii–Moriya interaction, and spin–spin interactions associated with the odd anisotropy of the symmetric exchange between magnetic ions mediated by nonmagnetic ions. The dependence of the electric polarization on the spin density and the tensor g-factor is derived within the generalized spin-current model. New contributions to the macroscopic electric polarization arising in cycloidal and helicoidal spin orders and induced by the off-diagonal components of the gyromagnetic tensor are predicted. The extension of the spin-current model to include a tensor g-factor may be important for magnetic ferroelectrics containing heavy ions that contribute significantly to the magnetoelectric effect.
In this study, we explore cosmological models that include bulk viscosity and a decaying vacuum energy density (VED) within an anisotropic, locally rotationally symmetric (LRS) Bianchi type I spacetime. The cosmological constant is expressed in a running-vacuum form as Λ=lḢ+(l+λ)H2+4πGηρm, where l, λ, and η are dimensionless parameters. The associated vacuum energy density is given by ρΛ=Λ/(8πG), which simplifies to ρΛ=lḢ+(l+λ)H2+12ηρm in natural units where 8πG=1. The viscous pressure is described using the non-causal Eckart theory, and we derive analytical solutions for both the Hubble parameter and the scale factor. We constrain the model parameters through Markov Chain Monte Carlo (MCMC) analysis, utilizing 31 Hubble parameter measurements and 1048 Pantheon supernova data points. Various cosmological parameters are calculated and compared with those from the standard ΛCDM model. Our findings indicate that the model captures the universe’s transition from a matter-dominated decelerating phase to an accelerating phase, as reflected in the behavior of the deceleration and equation-of-state (EoS) parameters. We show that the model is consistent with observational cosmological data and converges to the ΛCDM model at late times. Additionally, we apply model selection criteria such as AIC, BIC and DIC to evaluate the statistical robustness of the model. Overall, this approach provides fresh perspectives on the dynamics of varying vacuum energy density, emphasizing the decaying characteristic of dark energy and its significance in the evolution of the cosmos.
Taking the mass, charge, hair parameter, and cosmological constant of the 5-dimensional de Sitter hairy spacetime as the state variables of a thermodynamic system, and based on the satisfaction of the universal first law of thermodynamics, we obtain the effective thermodynamic quantities of the spacetime. The thermodynamic properties of the system in the coexistence region of the black hole and cosmological horizons are discussed. We find that under certain conditions, the heat capacity of the effective thermodynamic system in the two-horizon coexistence region of de Sitter hairy spacetime, as a function of either temperature or the ratio of the horizon positions, exhibits a peak-like behavior similar to that observed in paramagnetic systems. Further analysis reveals that, under specific conditions, the heat capacity of this effective thermodynamic system in dS spacetime resembles that of a two-level system composed of two horizons with different radiation temperatures. By comparing these results, we derive the expressions for the number of microscopic particles on the two horizons within the coexistence region, as N≈[3191+34.86(1/Λ−60)]6Λ×2.7k×102 and Ngrand≈16Λk[3191+34.86(1/Λ−60)]2.7−ϕeff−0.52.5×102 in the canonical ensemble and grand canonical ensemble, respectively (with Λ is the cosmological constant). This outcome reflects the quantum nature of dS spacetime and provides a new pathway for further in-depth investigation into the thermodynamic and quantum properties of the two-horizon coexistence region in dS spacetime.
We investigate a novel cosmological scenario by analyzing an anisotropic Bianchi Type I universe within the theoretical framework of f(Q) gravity. Our study introduces, for the first time in this context, the use of CoLFI (Cosmological Likelihood-Free Inference), a deep learning-based methodology for parameter estimation that does not rely on explicitly specified likelihood functions, thereby addressing key limitations of conventional inference techniques, including sensitivity to likelihood misspecification and the high computational cost associated with exploring complex, high-dimensional parameter spaces. To assess the robustness and accuracy of this framework, we benchmark its performance against traditional Markov Chain Monte Carlo (MCMC) analysis using a heterogeneous set of cosmological observations comprising 31 Cosmic Chronometer (CC) measurements of the Hubble parameter, Baryon Acoustic Oscillation (BAO) data, and the Pantheon＋ Type Ia supernova compilation. The CoLFI framework is trained and validated on an extended 57-point Observational Hubble Data (OHD) set. We find qualitative consistency between the cosmological dynamics inferred from the two approaches, with particularly close agreement in the inferred value of the Hubble constant. In the present study we work in the baseline f(Q)=Q limit, which is dynamically equivalent to the symmetric teleparallel equivalent of General Relativity (STEGR); the analysis is therefore methodological in scope, designed to introduce and validate the likelihood-free CoLFI pipeline for an anisotropic background against classical MCMC. These results highlight the substantial computational advantages of the deep learning-based approach and position CoLFI as a reliable and efficient tool for probing and constraining next-generation cosmological models.
In this inquiry, we study the new black holes of Lovelock-scalar gravity with Born–Infeld-type electrodynamics. First, we develop the family of charged hairy black hole solutions in dimensionally continued gravity. Next, the solutions characterizing charged hairy black holes in third order Lovelock gravity supported by Born–Infeld-type electrodynamics are figured out. In addition, we examine the thermodynamic properties and address the validity of generalized first law. The potential impacts of nonlinear electromagnetic field and scalar hair on the local stability in both canonical and grand canonical ensembles are explored as well.
We investigate the two-dimensional inhomogeneous Ising model (2DIM) on the kagom'e lattice by mapping it onto a particular non-symmetric eight-vertex model and constructing the corresponding R-matrix. Using a fermionic representation, we evaluate the partition function and derive explicit expressions for the main thermodynamic quantities. In the thermodynamic limit, we obtain an exact equation for the critical surface determining the phase transition of the model. We also calculate the free energy, specific heat, and spontaneous magnetization in the ferromagnetic case. Furthermore, we show that when one or two coupling constants vanish, the model reduces, respectively, to the square-lattice and one-dimensional Ising models. In both limits, our results reproduce the corresponding exact critical couplings and free energies.
We investigate thick brane scenarios within the framework of five-dimensional f(Q,T) gravity, where Q is the nonmetricity scalar and T is the trace of the energy–momentum tensor. We consider a non-canonical, factorized K-field matter sector. This model is not equivalent to the standard canonical scalar-field theory even in the linear case F(X)=X, and is therefore treated as an intrinsically non-canonical brane source. By deriving the modified field equations and implementing a first-order formalism, we obtain analytical solutions for various superpotentials and explore their consequences for the brane structure. We conduct a detailed analysis of gravitational perturbations, showing that the massless graviton zero mode is localized on the brane, ensuring the recovery of four-dimensional gravity. The effective potential for tensor modes exhibits a volcano-like structure supporting a localized massless graviton zero mode. The analysis of the massive spectrum indicates the presence of continuum Kaluza–Klein modes, with no clear evidence of quasi-localized resonant states for the parameter choices considered. For suitable values of the Yukawa coupling parameter η, the left-chiral fermion zero mode can be localized on the brane. Our results highlight the phenomenological effects introduced by non-canonical kinetic terms and matter-geometry coupling in f(Q,T) gravity.
We investigate a non-local electrodynamics model in the presence of a planar semi-transparent mirror. The theory is defined by supplementing Maxwell electrodynamics with a non-local operator that generates a Cornell-type confining interaction. We derive the exact gauge field propagator modified by the boundary and use it to obtain analytical expressions for the interaction energy and force between the mirror and a static point-like charge. The analysis is carried out in the different regimes determined by the parameter mμ, revealing a rich structure for the charge–mirror interaction. In all cases, the interaction energy displays a confining behavior, leading to a finite asymptotic force that is independent of the mirror transparency. This demonstrates that confinement is a robust consequence of the non-local dynamics rather than a boundary-induced effect. Comparisons with standard Maxwell electrodynamics highlight the novel features introduced by non-locality. Possible connections with spatially dispersive electromagnetic environments and experimentally accessible charge-surface systems are also discussed.
This work investigates the transmission probability (greybody factor) and the absorption cross section of bosonic particles in a black hole spacetime sourced by nonlinear ModMax electrodynamics and a global monopole within the framework of Lorentz-violating Kalb-Ramond gravity. We systematically analyze the dynamics of different bosonic field perturbations, including spin-0 scalar, spin-1 electromagnetic, and spin-2 fields, in this black hole background and derive the corresponding effective potentials. Using these effective potentials, the greybody factors are evaluated to understand how the geometrical parameters of the spacetime influence the propagation and scattering behavior of these fields. In addition, we investigate the thermodynamic properties of the obtained black hole solution. In particular, we analyze the ADM mass, Hawking temperature, Gibbs free energy, and specific heat capacity in order to characterize the thermal stability and phase structure of the system. The results show that the presence of the Lorentz-violating parameter, the global monopole contribution, the nonlinear electrodynamics parameter, and the electric charge significantly modify the thermodynamic behavior of the black hole, affecting the horizon structure, stability regions, and the occurrence of phase transitions.
