Modern Physics Letters A

The nuclear structure properties of heavy and superheavy nuclei lying at the extremes of charge, especially $Z=102\text{–}126$, and their density profiles have been explored using the relativistic Hartree–Bogoliubov in axial symmetry and the Skyrme–Hartree–Fock–Bogoliubov framework in transformed harmonic oscillator basis. In this study, we found that the semi-bubble (reduced central density) structure is mainly driven by Coulomb repulsion which stabilizes the nuclei either by pushing the nuclear matter in the surface region or by shape deformation. The shell effect is found maximum in spherical symmetric nuclei as the vanishing fission barrier in Liquid Drop formula indicates that the shell correction energy is responsible for the stabilization of these nuclei.

Among many models which can describe the bouncing cosmology, a matter bounce scenario that is deformed by a running vacuum model of dark energy (RVM-DE) has been interested. In this research, I show that a class of RVM-CDM (cold dark matter) model can also describe a cyclical cosmology in which the universe undergoes cycles of expansion to the contraction phase and vice versa. To this end, following our previous work, I consider one of the most successful classes of RVM-CDM model in bouncing cosmology, ${\rho }_x=n_0+n_2{H}^2+n_4{H}^4$, in which the power spectral index gets a red tilt and the running of the spectral index may give a negative value by choosing the appropriate value of parameters $(n_0$, $n_2$, $n_4)$, which is consistent with the cosmological observations. It is worthwhile to mention that most matter bounce models do not produce this negative value. However, the main purpose of this paper is to investigate the RVM-CDM model in the turnaround phase. Far from the bounce in a phantom expanding universe, the turnaround conditions are investigated before the occurrence of a sudden big rip. By analyzing the Hubble parameter, equation of state (EoS) parameter, and deceleration parameter around the turnaround, we show that a successful turnaround may occur after an expansion in an interacting case of RVM-CDM by choosing the appropriate value of parameters. A minimum value for the interaction parameter is obtained and also find any relation between other model parameters. Finally, the effect of each parameter on a turnaround is studied, and we see that the transition time from accelerating to decelerating expansion can occur earlier for larger values of interaction parameter. Also, in several graphs, the effect of the second term in DE density, including $H^2$, is studied, and we see that by increasing its coefficient, $n_2$, the transition point leads to lower values.

This paper is devoted to studying the structure of gravitationally vacuum condensate stars under the influence of matter and geometry coupled gravity. This alternative to black hole comprises three domains, i.e. interior, exterior and thin-shell. We investigate such regions by considering particular equations of state for a specific model of energy–momentum squared gravity. The nonsingular solutions of field equations are obtained to describe the interior region of gravastar and the Schwarzschild spacetime represents the exterior region. The junction conditions are used to match interior and exterior domains while Lanczos equations provide the surface density and pressure at thin-shell. We investigate various attributes of gravastar such as the equation of state parameter, entropy, proper length as well as energy. The physical features of a gravitationally vacuum star indicate a linear relationship with the thickness of the shell and provide a viable structure similar to general relativity.

The cosmological model executing hybrid expansion law (HEL) of scale factor in Randall–Sundrum type II (RS) braneworld gravity with Gauss–Bonnet terms in the presence of bulk viscosity described by Eckart theory, Truncated Israel–Stewart (TIS) theory, Full Israel–Stewart (FIS) theory and nonlinear Israel–Stewart (nIS) theory is studied. In the hybrid expansion law, the scale factor of the universe is described by the product of power-law and exponential expansions. In the HEL model, the early inflation and its transition from deceleration phase to present accelerated phase of expansion can be explored. The constraints of hybrid expansion law model parameters are determined using the recent observational data. Thereafter, the estimated parameters are considered to explore the present value of deceleration parameter, jerk parameter and transition epoch from early deceleration to the present accelerating phase.

In this paper, the $(G^{\prime }/G)$-expansion method is used to obtain two certain classes of one-parameter exact solutions to the null-geodesics in Ellis–Bronnikov wormhole spacetime. This method has been developed as an effective technique to construct exact analytical solutions for some kind of nonlinear evolution equations and nonlinear partial derivative equations (PDE). At the first stage of this method, a nonlinear PDE is transformed into nonlinear ordinary derivative equation (ODE) of a polynomial form. Therefore, if we initially have a nonlinear ODE of a polynomial form, say, the geodesic equation, then sometimes its solutions can be obtained following to the procedure of $(G^{\prime }/G)$-expansion method. Here, this method made it possible to obtain some classes of exact analytical solutions of null-geodesic equations in the metric of Ellis–Bronnikov wormholes.

To the best of our knowledge, for the first time, the quantum Hall effect (QHE) is considered in thermal non-equilibrium conditions (TNEC) via $q$-algebra. The $q$-algebra is a topological tool that provides a controlling $q$-parameter to approximate theoretical results to the laboratory ones. We obtain the QHE spectrum and $q$-deformed Hall potential (or Hall potential in TNEC) via the density probability current. Because of the Pauli Exclusion Principle, we model the QHE using relativistic Fermi electron gas and the $q$-deformed Fermi–Dirac distribution. We find the dependence of deformed Hall potential to temperature and magnetic field for different geometric $q$-regions. Further, we geometrically prove that the magnitude of the Hall potentials depends on the $q$-regions (i.e. $\left|V_H^{(q>1)}\right|>\left|V_H^{(q=1)}\right|>\left|V_H^{(q<1)}\right|$). We find that for some $q$-amounts, the Landau energy gap on graphene-based materials can be explained in the room-temperature quantum Hall effect (RTQHE). Our method may be applied to analyze new electronic devices based on graphene in TNEQ.

Recently, Cao et al. [Mod. Phys. Lett. A 34, 1950332 (2019)] presented a two-party quantum key agreement scheme using the five-qubit Brown states and the decoy protocol. They also extended their scheme to the multiparty case, and it was compared with existing works. The authors also introduced the security analysis that proves the security of their protocol against outsider and insider attacks. However, this work shows that the quantum Cao et al. [Mod. Phys. Lett. A 34, 1950332 (2019)] protocol fails to fulfill one of the most significant conditions of the quantum key agreement, which is fairness. The computed final key by the users does not have the same level of security, and the protection of users’ private data is not maintained equally. Finally, an improved version of Cao et al.’s protocol has been suggested.