Modern Physics Letters A

In this paper, we will use a unitary gravitational action up to third-order of curvature with respect to the holographic a-theorem. In particular, its third-order term has a Weyl-cubed term.

In this paper, we study this Weyl-cubed theory and find some of its exact classical solutions. We show that the theory admits conformally flat, Lifshitz, Schrödinger and also hyperscaling-violating backgrounds as the solutions of the equations of motion. Our analysis has been done for the pure Weyl-cubed gravity, Einstein plus Weyl-cubed term and gravity with matter.

By neglecting the effects of self-force and radiation, we investigate the possibility of destroying the Kerr-MOG black hole through the point particle absorption process. Using the instability of event horizon and equation of particle motion, we get the upper and lower energy bounds allowed for a matter particle to produce the naked singularity. We find that the energy gap always exists between the upper and lower energy bounds for both extremal and near-extremal black holes, which means some tailored particles can actually lead to the violation of the weak cosmic censorship conjecture. However, when considering the effect of the adiabatic process, the result shows that the Kerr-MOG black hole gets more stable instead of a naked singularity, and thus the weak cosmic censorship conjecture can be restored at some level.

In this paper, stellar hydrostatic equilibrium configuration of the compact stars (neutron stars and strange stars) has been studied for $f({𝒢},T)$ gravity model, with ${𝒢}$ and $T$ being the Gauss–Bonnet invariant and the trace of energy–momentum tensor, respectively. After deriving the hydrostatic equilibrium equations for $f({𝒢},T)$ gravity, the fluid pressure for the neutron stars and the strange stars has been computed by implying two equation of state models corresponding to two different compact stars. For the $f({𝒢},T)=\alpha {{𝒢}}^n+\lambda T$ gravity model, with $\alpha$, $n$, and $\lambda$ being some specific parameters, substantial change in the behavior of the physical attributes of the compact stars like the energy density, pressure, stellar mass, and total radius has been noted with the corresponding change in $\lambda$ values. Meanwhile, it has been shown that for some fixed central energy density and with increasing values of $\lambda$, the stellar mass both for the neutron stars and the strange stars increases, while the total stellar radius $R$ exhibits the opposite behavior for both of the compact stars. It is concluded that for this $f({𝒢},T)$ stellar model, the maximum stellar mass can be boosted above the observational limits.

In this paper, alpha decay half-lives of spherical nuclei in the range $67\le Z\le 91$ are studied by considering the Coulomb and proximity potential model (CPPM) and calculating the alpha particle preformation factor. Comparisons are made to existing data in the literature. The half-lives are compared to the experimental values and also with the existing theoretical models, the analytical formula of Royer (R) and also within the modified analytical formula of Royer (MR) and New Akrawy–Poenaru Formula (AKRE) by Akrawy and Poenaru and the semi-empirical model based on fission theory (SemFIS) of Poenaru et al., the Universal Decay Law (UDL) of Qi et al., the Scaling Law of Brown (SLB), the Scaling Law of Horoi et al. (SLH). Compared with the experimental alpha half-lives, it can be found that the half-lives obtained using our formalism is in good agreement with the experimental data.

Tsukamoto [N. Tsukamoto, Phys. Rev. D 95, 064035 (2017)] developed a method, which is an improvement over that of Bozza [V. Bozza, Phys. Rev. D 66, 103001 (2002)], for calculating light deflection angle in the strong gravity field of a spherically symmetric static spacetime. The method is directly applicable to the massless Ellis–Bronnikov wormhole (EBWH), while Bozza’s method is not applicable. We wish to show that it is still possible to obtain the same deflection angle by applying Bozza’s method but only in an indirect way, that is, first calculate the deflection by the parent massive EBWH and then take its massless limit.

We present here polarization operator of non-relativistic fermions with spin-orbit (SO) Rashba interaction. The spectrum of this fermions is moat type having minimum on a circle. Contrary to Dirac or non-relativistic fermions, Fermi sea here has a geometry of Corbino disk which reflects in a transport properties of excitation’s.

In this research paper, we address the issues of expansion and gravitational collapse of anisotropic spherical source in the presence of cosmological constant. For this purpose, we have solved the Einstein field equations with gravitating source and cosmological constant. The absence of radial heat flux in the gravitating source provide the parametric form of two-metric functions in terms of a single-metric function. The expansion scalar and the mass function of the gravitating source is evaluated for the given metric. The trapping condition is applied to mass function which implies the existence of horizons, like the horizons of Schwarzschild de-Sitter black holes. The trapping condition provides the parametric form of the unknown metric function. The value of expansion scalar has been analyzed in detail to see its positivity and negativity, which correspond to expansion and collapse, respectively. So, the values of parameter $\alpha$ for which expansion scalar is positive have been used to analyze the other physical variables including density, pressures and anisotropy. The same quantities have been evaluated for the values of $\alpha$ that result in the negative values of expansion scalar leading to collapse. The effects of positive cosmological constant have been noted in both expansion and collapse solutions. Due to the presence of cosmological constant after collapse, there would occur inner and outer horizons or a unique horizon depending on the value of mass of the gravitating source.