Modern Physics Letters A

The estimation of the Hubble constant in the past few decades has increasingly become more accurate with the advancement of new techniques. However, its value seems to depend on the epoch at which the measurements are made. The Planck estimate of the Hubble constant from the observations of the cosmic microwave background radiation in the early universe is about $67\mathrm{\text{km}}\backslash \mathrm{\text{s}}\backslash \mathrm{\text{Mpc}}$, whereas that obtained from the distance indicators at the current epoch is $\sim 73-74\mathrm{\text{km}}\backslash \mathrm{\text{s}}\backslash \mathrm{\text{Mpc}}$. This discrepancy between the two groups of measurement is termed as the Hubble tension which has gained much attention in the past few decades with growing significance as measurements from both, the early and the late universe, studies continue to produce results with increasing precision. In this work, we propose a modification to gravity by considering a finite range gravitational field as an alternate explanation for this discrepancy in the value of the Hubble constant.

In this paper, we investigate the properties of a five-dimensional Ricci-flat black hole within the framework of the Space–Time–Matter theory. By employing the Klein–Gordon equation, we derive the wave function equations for both the mass dimensional coordinate and the radial dimensional coordinate. We present the analytical solutions for the wave function on the mass dimensional coordinate under two distinct scenarios. Remarkably, we observe the absence of quantum effects on the mass dimensional coordinate, which aligns with the absence of a barrier in the wave function equation. For the radial component, we employ the B-spline method to numerically solve its wave function. Our findings reveal the existence of Hawking radiation between the event horizon and the cosmological horizon, with the transmission and reflection probabilities being determined by the presence of a barrier. Furthermore, we discover a significantly higher probability of particle detection near the cosmological horizon, while the probability near the event horizon approaches zero.

Einstein’s gravity in AdS space coupled to nonlinear electrodynamics (NED) with two parameters is studied. We investigate magnetically charged black holes. The metric and mass functions and their asymptotic are obtained showing that black holes may have one or two horizons. Thermodynamics in extended phase space was studied and it was proven that the first law of black hole thermodynamics and the generalized Smarr relation hold. The magnetic potential and the vacuum polarization conjugated to coupling (NED parameter), are computed and depicted. We calculate the Gibbs free energy and heat capacity.

Recently, the precise observations have yielded values for the neutrino mixing angles, denoted as ${\theta }_{12}$ and ${\theta }_{13}$. Therefore, constructing a neutrino mixing model capable of accurately reflecting these measurements is crucial. In this paper, we propose a novel neutrino mixing model similar to the trimaximal mixing model. Unlike the trimaximal model that falls short of concurrently replicating the best-fit values of ${\theta }_{12}$ and ${\theta }_{13}$, our proposed mixing model has the ability to simultaneously reproduce the best-fit values for both angles.

By mapping the scalar Helmholtz equation (SHE) to the Schrödinger form we investigate the behavior of $\mathcal{𝒫}\mathcal{𝒯}$ optical structure when the refractive index distribution n admits variation in the longitudinal direction only. Interpreting the Schrödinger equation in terms of a superpotential we determine the supersymmetric partners for n. We also obtain new analytical solutions for the refractive index profiles and provide graphical illustrations for them.

The aim of this paper is to investigate the dynamical behavior of a Carbon atom under the forces of the two fullerenes in the circular restricted three-body (CR3B) configuration with nanoscale. Here, we assume that the mass of a Carbon atom varies according to the Jeans law, and then with the use of Meshcherskii transformation, we determine the equations of motion and quasi-Jacobian integral. Then by the use of numerical values of the parameters, we investigate the potential surfaces, equilibrium points, regions of motion, Poincaré surfaces of sections, periodic orbits, basins of attraction and stability of the equilibrium points.

Most semi-quantum secret sharing protocols are suitable for the application with three participants. Based on the n-level states, a multiparty semi-quantum secret sharing protocol is proposed. Compared with similar protocols, it has the merits as follows. (1) The dealer only needs to prepare the single photon sequence without using any product state or entangle state. (2) To share a secret, the classical parties need not have the ability of measurement. They only need to reorder the photon sequence and send it to the receiver. (3) The dealer knows nothing about any agent’s secret shadow. Therefore, it is infeasible for the dealer to impersonate the classical participant to pool the secret shadow during the secret recovering phase. (4) Theoretically, the qubit efficiency of the proposed protocol is asymptotically 100%. The protocol is secure against famous attacks such as intercept-resend attack, measurement-resend attack and entangle-measure attack.

In this paper, we study the evolution of Bianchi-I spacetimes within the framework of the Horndeski theory with $G_5=\mathrm{\text{const.}}/X$. The spacetimes are filled a global unidirectional electromagnetic field interacting with a scalar field. We consider the minimal interaction and the non-minimal interaction by the law $f^2(\varphi )F_{\mu \nu }{F}^{\mu \nu }$. The Horndeski theory allows anisotropy to grow over time, so the question arises of regulating the anisotropic level in this theory. Using the designer method, we build models in which the anisotropic level tends to a small value as the Universe expands. One of the results is a model with a anisotropic bounce.

In order to alleviate the Hubble tension, we propose a new law for the Hubble parameter that varies periodically with time and we study the validity of the dynamics of a flat Friedmann–Robertson–Walker Universe in the context of a generalized Chern–Simons modified gravity (CSMG). We prove that for specific numerical values of the free parameters in the theory, the phantom divide line is crossed and the universe undergoes decelerating expansion and accelerating expansion alternately without singularity. The deceleration and the jerk parameters oscillate also around numerical values in agreement with astronomical BAO+Pantheon SNeIa+Cosmic Chronometers observations.

A Thorne–Żytkow object can be formed when a neutron star is absorbed by the envelope of its giant companion star, spirals toward the center of the giant star due to the drag from the surrounding envelope, and merges with the star’s core. During in-spiral, dynamical friction is the main drag force acting on a neutron star inside the star envelope. However, dynamical friction is caused by the neutron star’s gravitational interaction with its own gravitationally induced wake. Therefore, exactly, the same gravitational drag force will act on a mirror neutron star, and if a significant part of the dark matter is in the form of mirror matter, then we expect the formation of Thorne–Żytkow objects with a mirror neutron star inside. We explore the plausibility of the existence of such exotic Thorne–Żytkow objects.