This paper examines dark-energy compact stars under the paradigm of modified Rastall teleparallel gravity. This is the primary analysis of dark energy celestial phenomena under this modified gravitational theory. Utilizing the torsion-based functions, [Formula: see text] and [Formula: see text], we examined their impacts within a spherically symmetric space-time designated as the inner geometry, while employing the Schwarzschild geometry as the outside space-time. This study examines several features of dark energy in stars, encompassing dark energy pressure components, energy conditions, and equation of state components. Our findings indicate that the detected adverse behavior of certain stellar parameters provided substantial evidence, ensuring the presence of dark energy in celestial configurations. Thorough examinations of energy conditions, pressure profiles, sound speeds, adiabatic index, gradients, mass function, compactness, and redshift function provide a full evaluation, confirming the viability and authenticity of the analyzed stellar configuration.

In this work, we investigate the dynamical and thermodynamic characteristics of a static, spherically symmetric black hole (BH) immersed in an anisotropic fluid within the framework of an extended theory of gravity. The spacetime geometry is specified by the metric function h(r), which depends on the parameters a, b, k, and w, as well as on the cosmological constant Λ. In this case, using the Hamiltonian formalism, the motion of neutral test particles is analyzed through the effective potential, leading to analytical expressions for the specific energy, angular momentum, and effective force. The position of the innermost stable circular orbits (ISCOs) is obtained, showing that increasing a, b, and w deepens and narrows the potential well, moving the ISCOs closer to the horizon and strengthening the gravitational attraction compared to the Schwarzschild case. Small perturbations around stable orbits yield the fundamental frequencies, which increase with the coupling parameters, suggesting a link with quasi-periodic oscillations (QPOs). In this context, using the Barrow entropy formalism, we compute the geometric mass, Hawking temperature, and entropy, showing that a, b, k, w, and Λ affect the thermal stability and emission rate of the BH.

We develop a finite-distance framework for vacuum birefringence in static, spherically symmetric spacetimes threaded by strong magnetic fields. In the geometric optics limit of nonlinear electrodynamics, the two photon polarizations propagate along null geodesics of distinct effective (optical) metrics. Using a controlled weak-coupling expansion, we isolate the polarization dependent correction to the standard gravitational deflection and obtain a general expression for the differential bending angle Δα ≡ α + − α − . with the source and observer at arbitrary radii. The derivation is based on a finite-distance Gauss-Bonnet construction on the polarization dependent optical manifolds, thereby extending the usual scattering at infinity treatment. As an examples, we apply the formalism to Euler-Heisenberg QED and to Born-Infeld electrodynamics, the latter providing a non-birefringent consistency check with Δα BI = 0. We show that finite-distance truncation of the curvature flux generically suppresses the observable birefringence and provide explicit series corrections suitable for data analysis. For magnetar motivated field falloff and near surface emission, the suppression can reach the level of tens of percent and may approach ~ 1/2 for near-limb, outward only trajectories. These results supply an essential finite-distance calibration for interpreting X-ray polarimetry measurements and for placing unbiased constraints on strong-field QED and broader NLED parameters.

In this work, we present a general framework for obtaining exact solutions to the symmetric teleparallel gravity field equations describing strange stars obeying a colour-flavour-locked (CFL) equation of state. This study examines four star candidates: PSR J1614-2230, RXJ1856-37, HER X-1, and SAX J1808-3658. These stars have masses of 1.3 M ⊙ , 0.9031 M ⊙ , 0.98 M ⊙ , and 0.9 M ⊙ , respectively, and radii of 7.259 km, 6 km, 6.7 km, and 7.26 km, respectively. In our study, we solve the f(Q) gravity field equations by assuming a specific metric ansatz g rr component, and evaluate the g tt component by using the colour-flavour-locked (CFL) equation of state. We calculate the exterior spacetime using the principle of f(Q) gravity. The matching of the interior solution with that of the exterior spacetime is employed to determine the model parameters for given realistic compact stars. In this research, we study some properties of stellar models such as the behavior of the density and pressure components, the energy conditions, the metric components, the equation of state components, the sound speeds, the adiabatic index, the gradients, the mass function, the compactness, and the redshift function. Additionally, we examine the stability and equilibrium of the proposed stellar configuration. Our detailed theoretical analysis justifies the realism and feasibility of the stellar configuration considered by demonstrating that the proposed model is free of singularities and satisfies all stability requirements.

In this work, we study a vector dark energy (vDE) model within the framework of a flat Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime. By using the Noether symmetry approach, we obtain analytical cosmological solutions. The vDE model includes a vector field [Formula: see text] coupled to gravity through an arbitrary coupling function [Formula: see text] and a potential function [Formula: see text], which are determined by imposing Noether symmetry conditions. These conditions yield specific forms for the coupling and potential functions, enabling the simplification of the dynamical system. By introducing new variables [Formula: see text] and [Formula: see text], we solve the field equations and obtain exact solutions for the scale factor [Formula: see text] and the vector field parameter [Formula: see text]. In this paper, we adopt the potential function in the form [Formula: see text] and derive solutions for general [Formula: see text]. We specifically examine the cases [Formula: see text] and [Formula: see text], which produce physically viable results consistent with late-time cosmic acceleration. Graphical representations of the scale factor, vector field parameter, and equation of state demonstrate the transition from a matter-dominated era to an accelerated expansion phase, with the equation of state approaching [Formula: see text], resembling a cosmological constant. This paper suggests that the vDE model is a proper candidate for dark energy.

The purpose of this paper is to study the impact of plasma on the shadow of a charged, static and spherically symmetric black hole in [Formula: see text] gravity. Plasma surrounding black holes can affect the propagation of light rays, influencing the observed shape and size of the black hole shadow. To explore this phenomenon, we formulate the radius of photon sphere, the angular size of the shadow and radius of shadow in low-density plasma. We find that the size of shadow becomes smaller in the presence of plasma. The observed reduction in the size of the shadow in the presence of plasma can be attributed to the interaction between light and the plasma medium. The study of the rate of energy emission is also investigated in the presence of plasma medium and we find the peak position shifts from high to low frequency. The reduction in the rate of energy emission due to plasma can affect the dynamics of these accretion disks. We explore the angular radius for distant observer which has a decreasing behavior.

In this paper, we analyze the dynamics of charged test particles in a singular, horizonless spacetime arising as the massless limit of a charged wormhole in the Einstein–Maxwell–Scalar (EMS) framework. The geometry, sustained solely by an electric charge [Formula: see text], features an infinite sequence of curvature singularity shells, with the outermost at [Formula: see text] acting as a hard boundary for nonradial motion, while radial trajectories can access it depending on the particle’s charge-to-mass ratio [Formula: see text]. Exploiting exact first integrals, we construct the effective potential and obtain circular orbit radii, radial epicyclic frequencies, and azimuthal precession rates. In the weak-field limit ([Formula: see text]), the motion reduces to a Coulombic system with small curvature-induced retrograde precession. At large radii, the dynamics maps to a hydrogenic system, with curvature corrections inducing perturbative energy shifts. Approaching [Formula: see text], the potential diverges, producing hard-wall confinement. Curvature corrections also modify the spectral thermodynamics, raising energies and slightly altering entropy and heat capacity. Our results characterize the transition from Newtonian-like orbits to strongly confined, curvature-dominated dynamics.

The four-dimensional Einstein–Gauss–Bonnet theory of gravity developed by Glavan and Lin (Phys. Rev. Lett. 124 (2020) 081301) has been amply demonstrated to be applicable to spherically symmetric distributions, notwithstanding its other criticisms. This formulation allows us to study the effects of higher curvature geometry on the evolution of stars in the traditional four-dimensional setting. In particular, our interest in this paper is charged distributions. Despite the fact that the associated Einstein–Maxwell–Gauss–Bonnet field equations require two prescriptions to close the system, the task of locating exact solutions is nontrivial. We exploit a technique relating the electric field intensity to one of the gravitational potentials in order to reduce the order of the governing differential equation, and in this context we construct the isothermal fluid configuration exhibiting an inverse square law fall off of the energy density, and for a choice of integration constants also admits a similar behavior in the pressure. In general, the higher curvature terms negate the isothermal behaviour when the spatial metric potential is constant, unlike the Einstein case. The model constructed is shown to have the necessary qualitative features of realistic distributions as depicted in graphical plots for suitably selected parameter spaces. Notably a surface of vanishing pressure is evident and the model is adiabatically stable and causal. Given the isothermal feature, a central singularity is present as expected. This suggests that our fluid model may be interpreted as a shell of charged fluid in [Formula: see text] EMGB enveloping some other physically viable core.

In this paper, we investigate quantum gravitational corrections to Schwarzschild black hole thermodynamics by combining Barrow entropy with spin-dependent effects of the generalized uncertainty principle (GUP) within the tunneling formalism. By incorporating Zitterbewegung dynamics into the deformed Hamilton–Jacobi equation, we derive a spin-sensitive modification of the Hawking temperature that depends explicitly on the spin of the particle [Formula: see text] and the GUP parameter [Formula: see text]. This corrected temperature is used to compute thermodynamic quantities in the extended phase-space framework, including internal energy, Helmholtz free energy, pressure, enthalpy, Gibbs potential, and heat capacity. Our analysis reveals that quantum deviations from the classical Schwarzschild behavior emerge only in the small-radius regime ([Formula: see text]), while semiclassical results are recovered at larger scales. The Barrow fractal parameter [Formula: see text] introduces additional modifications to the phase structure, producing local minima in the Gibbs potential that signal possible metastable remnant states. We examine the Joule–Thomson expansion to characterize the cooling-heating phase diagram and identify inversion curves where the thermal response changes qualitatively. The results show that higher-spin particles deepen the cooling regime and shift phase boundaries, indicating that the dominant emission channel during late-time evaporation influences the black hole’s approach to its final configuration. The combined action of [Formula: see text] suggests that spin-dependent quantum corrections play a decisive role in determining remnant masses and testing minimal-length scenarios in near-Planckian black holes.

In this work, we numerically investigate the cosmological evolution of a non-minimal derivative coupling model with a scalar potential term coupled to the Ricci scalar. Specifically, we focus on the late-time cosmology of the John–George field model. By adopting the FLRW metric, we derive the equations of motion corresponding to the scalar field configuration. We then construct a system of equations, which is solved numerically using two well-known types of potentials from the literature: the power-law potential and the exponential potential. To characterize the dynamics, we evaluate key cosmological quantities such as the Hubble parameter, the statefinder diagnostic, and dark energy indicators including the equation of state and energy density. The numerical evolution of these parameters reveals a phenomenology consistent with the latest Planck 2018 observations. Moreover, the model successfully reproduces the behavior of the standard [Formula: see text]-Cold Dark Matter ([Formula: see text]CDM) cosmological model, supporting its viability as an alternative framework for describing late-time cosmic acceleration.