This paper examines Locally Rotationally Symmetric (LRS) Bianchi type-V cosmology with a variable Chaplygin gas equation of state, [Formula: see text]. The analysis adopts a late-time, weak-anisotropy approximation, defined by [Formula: see text]; it is not a nonperturbative treatment of arbitrary shear. The field equations used for the dynamical and observational analyses are truncated at the stated perturbative order. Within this regime, the analysis estimates an approximately [Formula: see text] shear suppression relative to General Relativity and identifies an isotropic de Sitter attractor. An MCMC analysis using Hubble-parameter measurements, the Pantheon+ Type Ia supernova sample, and baryon acoustic oscillations gives [Formula: see text] km s[Formula: see text] Mpc[Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]. However, the information-criterion comparison does not favor this extended model over [Formula: see text]CDM ([Formula: see text]AIC [Formula: see text] and [Formula: see text]BIC [Formula: see text], defined as the extended-model value minus the [Formula: see text]CDM value). The quoted shear suppression, parameter constraints, model comparisons, and predicted anisotropic imprints ([Formula: see text]) are conditional on [Formula: see text] and should not be extrapolated to strongly anisotropic solutions.
This study explores the dynamics of late-time cosmic acceleration through the lens of non-minimally coupled [Formula: see text] modified gravity. In this framework, an explicit coupling is introduced between the non-metricity scalar Q and the matter Lagrangian density [Formula: see text]. We consider a specific nonlinear functional form of the theory to derive the modified Friedmann equations governing cosmic evolution. To obtain an exact analytical solution for the Hubble parameter [Formula: see text], we employ a parameterization technique where the effective equation of state (EoS) of the model is equated to a logarithmic parametrization form, given by [Formula: see text]. We constrain the model’s free parameters by performing a Bayesian statistical analysis using Markov Chain Monte Carlo (MCMC) methods, utilizing a combination of observational datasets, specifically cosmic chronometers (CC) and dark energy spectroscopic instrument (DESI)-baryon acoustic oscillations (BAO). Further, we reconstruct the evolution of kinematic quantities such as the energy density, pressure, and the deceleration parameter [Formula: see text], which exhibits a smooth transition from a decelerated epoch to the present accelerated phase. Additionally, we analyze the behavior of the effective EoS to distinguish between quintessence-like and phantom-like regions. The geometrical diagnosis of the model is performed using the Om[Formula: see text] diagnostic and higher-order cosmographic parameters, including the Jerk, Snap, and Lerk, as well as the State-finder hierarchy. Further, the violation of the strong energy condition (SEC) validates the accelerating behavior of the universe, while the model remains consistent with other stability criteria. Our findings suggest that our gravity model serves as a viable alternative to the [Formula: see text] CDM model.
The present paper investigates whether teleportation provides a higher quality of state transfer than direct transmission through the same noisy channel. We consider bit-flip, phase-flip, amplitude-damping, phase-damping, and depolarizing noises for the transfer of Bell-like and GHZ-like states, under both distance-dependent and time-dependent noise models. Our results show that the relative advantage of teleportation depends strongly on the noise channel and noise model. For the Bell-like state, teleportation remains superior throughout the distance-dependent model for BF, AD, and PD noise, whereas PF and DP exhibit limited regions favoring direct transmission. For the GHZ-like state, teleportation remains superior throughout for PD and DP noise, while BF, PF, and AD show parameter-dependent behavior. The time-dependent model further modifies these trends due to the additional decoherence associated with the waiting time for classical communication. We also compare the teleportation fidelities with the classical measure-and-prepare benchmark 2/3, revealing channel-dependent regions in which the classical limit is surpassed. These findings highlight the role of noise structure and communication time in determining the conditions under which teleportation provides an advantage over direct transmission.
In relativistic geometric optics, massless radiation propagates along null geodesics, while caustics arise where neighboring ray labels lose resolution. We study this focusing mechanism on the lightcone of a point event in four-dimensional Minkowski spacetime. Starting from an eikonal phase, we use an affine spacelike section of the cone as a screen of normalized propagation directions. A one-parameter anisotropic emission profile on this screen generates two lightcone dual surfaces, interpreted as families of spacelike wavefront cuts selected by stationary Lorentzian contact. Their induced metrics give exact transverse area Jacobians, so the vanishing of a Jacobian identifies kinematic focusing independently of spacetime curvature. The normalized hyperbolic curvature [Formula: see text] of the emission profile controls caustic onset and local morphology. Generic real caustic branches occur for [Formula: see text], while [Formula: see text] is a degenerate threshold for the second family. Along a generic caustic, [Formula: see text] produces a stable cuspidal ridge, whereas [Formula: see text] and [Formula: see text] produce a swallowtail transition. These results separate focusing caused by the organization of null propagation directions from Ricci or Weyl focusing and provide a flat-spacetime reference for geometric-optics caustics and their extension to curved null hypersurfaces.
This study formulates the greybody factor for a charged non-commutative Schwarzschild black hole embedded in a perfect fluid dark matter. A minimally coupled massless scalar field is initially considered to study the emission rate of the black hole. We obtain the radial equation by applying the Klien-Gordon equation of motion via separation of variables method. The radial part of the wave equation is then transformed through the introduction of the tortoise coordinate, allowing it to be expressed in a Schrödinger-like form. Afterwards, we study the effects of the involved parameters on the effective potential. We also obtain analytical solutions of the radial equation near the event and asymptotic horizons, and match these solutions in a middle region to obtain the expression for greybody factor. The graphical analysis indicates that an increase in the non-commutative parameter reduces this factor at higher frequency modes. Further, an increase in charge enhances this reduction, while the mass parameter contributes to moderating the radiation. Overall, the interplay between charge, non-commutativity and perfect fluid dark matter increase the evaporation process and shorten the life span of the considered black hole as compared to classical Reissner-Nordström and Schwarzschild solutions.
