Modern Physics Letters A

In statistical theory, the Tsallis entropy is an extended form of the Boltzmann–Gibbs entropy. The dimensionless parameter $\delta$ is employed to state the quantitative difference from the standard scenario. The concepts of Tsallis entropy and the future event horizon are employed in formulating the present new Tsallis holographic dark energy (NTHDE) model. The model attempts to explain the properties of dark energy using the foundation of quantum gravity. The differential equation characterizing the evolution of the NTHDE density parameter is obtained. Expressions stating the dynamic behavior such as equation of state (EoS), deceleration and jerk parameters are obtained in terms of the NTHDE density parameter. For $\delta <1$, the quintessence nature of scalar field could completely characterize the NTHDE. A reconstruction of the scalar field’s dynamics and quintessence potential is attempted. We demonstrate that the diagnosis made by statefinder is adaptive enough to distinguish between quintessence and cosmological constant-based dark energy models. Additionally, observational data obtained from CC$+$ SNIa $+580$ union 2.1 sources are used to evaluate the model’s effectiveness.

The early Universe was characterized by the presence of heavy particles that decoupled at different temperatures leading to different phases of the Universe. This had some consequences on the time evolution of the thermodynamic and the cosmological parameters characterizing each phase of the early Universe. In this study, we derive the analytic expressions of the equations governing the time evolution of these parameters using the equations of state of the MIT bag model describing the quark–gluon plasma era. In addition, using the equations of state derived from considering the recent results of the lattice QCD simulations, we solve numerically the differential equation governing the time evolution of the energy density in the early Universe. The time evolution of the parameters under concern including the energy density, entropy density, temperature, pressure in addition to Hubble parameter and scale factor can then be estimated as will be presented in this work.

In this paper, we study the Dirac particle near the event horizon of the charged Bañados-Teitelboim-Zanelli (BTZ) black hole and Reissner–Nordström (R-N) black holes to obtain its energy spectrum for discussing the weak gravity conjecture (WGC). The corresponding energy has both real and imaginary parts. We encounter the quasi-normal mode. Because the considered black holes have mass $M$ and charge $Q$, this property allows us to examine the WGC using the energy spectrum with specific conditions. We attempt to investigate the WGC for these black holes by utilizing the Dirac particle energy spectrum obtained near charged black holes. Also, we impose conditions on the energy spectrum of particles for which the WGC holds for charged black holes, i.e. $Q∕M>1$. To approve the WGC near the event horizon of black holes, we determine that the Dirac particle has a specified charge viz $q=-\frac{1}{2\omega }$ and $q=-\frac{1}{ln(\frac{r_{+}}{\ell })}$ for R-N and charged BTZ black holes, respectively.

This paper examines the structure of a gravitational vacuum star (also known as gravastar) in the background of $f(\Re ,{{𝒯}}^2)$ theory. This hypothetical object can be treated as a substitute of a black hole, with three regions: (i) the internal region, (ii) the intrinsic shell and (iii) the outer region. We examine these geometries using Finch–Skea metric for the radial metric component along with the particular $f(\Re ,{{𝒯}}^2)$ model. We determine singularity-free solutions for both the inner as well as thin-shell domains. The smooth matching of the interior region with external Schwarzschild spacetime is obtained through Israel matching constraints. Finally, we study various characteristics of gravastar domains including the equation-of-state parameter, proper length, entropy, energy as well as surface redshift. It is found that the compact gravastar structure is a viable alternate to the black hole in the perspective of this gravity.

One interesting way to extend the Standard Model is the hypothesis of bifermions which are bosons that couple to pairs of quarks and leptons. We point out that $\mathrm{\text{SU}}(15)$ grand unification gives a natural way to classify bifermions and discuss leptoquarks, biquarks and bileptons. In fact, $\mathrm{\text{SU}}(15)$ provides an ideal covering group as it contains all possible bifermions within a single model.

In this work, we study the RVB method for calculating the Hawking temperature of different black holes and find that there is an undetermined integral constant in the temperature expression. We use this method to calculate the Hawking temperature of the black hole in Einstein gravity, and massive gravity, Einstein–Gauss–Bonnet gravity, Scalar–Tensor–Vector modified gravity and $f(R)$ gravity, respectively. By comparing with the temperature obtained by the Hawking temperature formula, we find that regardless of the gravitational theory from which the black hole solution is obtained, after the black hole metric is reduced to two dimensions, if there is no first-order term of $r$ in $g_{00}$, the integral constant is 0. If there is a first-order term of $r$ in $g_{00}$, the integral constant is determined by the coefficient in front of the first-order term of $r$.

The efficiency of the fractional state that is generated between a single atom and field by using anti-Jaynes–Cummings model (AJCM) is discussed. The fractional degree and the interaction parameters may be used as controllers to increase the efficiency of the fractional state in the context of quantum communication. It has been shown that, the quantum correlation, capacity, and the ability of the fractional state, increase suddenly/gradually at small/large fractional degree, respectively. At small fractional orders, the constant behavior for all these phenomena is displayed at a short interaction time. The fractional quantum state that is generated by the anti-Jaynes–Cummings model is more efficient than that generated by the well-known Jaynes–Cummings model (JCM), where it can be used to teleport an unknown two-qubit state with larger fidelity.

Lepton flavor violation (LFV) is one of the most trending topics to probe new physics (NP). The powerful accelerators have enhanced their intensities to observe the LFV decays very precisely. In this situation, the theorists are also interested in studying these decays in various NP models and in model-independent ways to get precise results. Motivated by these results we have studied $B\to K_2^{\ast }(1430)l_1{l}_2$ decays in non-universal $Z^{\prime }$ model. Here, we have structured the two-fold angular distribution of the decays in terms of transversity amplitudes and the transversity amplitudes are formed with NP Wilson coefficients. The variation of the branching ratios and forward–backward asymmetries show the sensitivity of NP. The observables calculated in this work are very interesting and might provide a new way towards NP.