Modern Physics Letters A

Neutrino flavor mixing is explained within the recently proposed low-scale minimal linear seesaw model of neutrino mass generation, a variant of the standard linear seesaw led by a Dirac pair of extra sterile neutrinos which is odd under a discrete $Z_2$ symmetry and has a mass at or below the GeV scale. The tri-bimaximal mixing and its deviations are derived straightforwardly on the basis of the symmetry between $\mu$ and $\tau$ flavors, without introducing non-abelian discrete flavor symmetries in the first place.

We present a family of nonlinear electrodynamics models that are free of the infinite self-energy of the point charge. Each model is dependent on a dimensional nonlinearity parameter and is determined by the integer value of a dimensionless parameter $n$. The Born–Infeld model is recovered when $n=1$. Some of the characteristics of this family are studied. In addition, we study the solutions of electrically charged AdS black holes, which result from coupling these electrodynamic models to General Relativity. A Smarr formula consistent with the first law of thermodynamics is also obtained in an extended phase space.

In recent years, a class of compact objects called gravastars have drawn immense interest as regular solutions to end state stellar collapse. Since the energy density involved in collapse process is expected to be high, it is a natural choice to study such compact objects in context of modified gravity theories which reduce to General Relativity (GR) in the low energy regime. We have already framed a model of gravastar in such a modified gravity framework involving extra dimensional Randall–Sundrum (RS) single brane gravity [R. Sengupta, S. Ghosh, S. Ray, B. Mishra and S. K. Tripathy, Phys. Rev. D 102, 024037 (2020)]. As a sequel in this paper, we substantially improve our previous model by choosing the Kuchowicz function as one of the metric potentials, which leads to many new interesting results and physical features from our analysis as discussed in this paper. Also, we provide essential additional stability checks on our gravastar model to investigate the possibility of any instability creeping in due to the higher-dimensional framework. Our present improved gravastar model is found to clear all the stability checks successfully. Very interestingly, the static spherically symmetric matter distributions are found to accommodate both classes of solutions obeying and violating the modified energy conditions on the RS brane as we find in this work. We can conclude from our analysis that the Kuchowicz metric potential is very effective for describing regular solutions to compact objects at substantially high energies on the three-brane.

The main purpose of this paper is to study the physical characteristics and stability of anisotropic compact stars in energy–momentum squared gravity. We use Tolman $𝕍$ solution and consider specific models of this theory to study the viable features of SAX J1808.4-3658, 4U 1538-52 and Her X-1 stars. We explore the behavior of energy density, pressure components, anisotropic factor, energy conditions and equation of state parameter in the interior of considered stars. To check the stability of these stars, we examine the behavior of causality conditions, Herrera cracking approach and adiabatic index. It is found that all the required conditions are satisfied for the proposed models, thus the considered stars are viable as well as stable in this modified theory.

In this paper, we analyze the tidal effects of anti-de Sitter charged black holes. The tidal force components are obtained by Riemann tensor on tetrad basis and geodesic deviation equation. The radial components of tidal force have the same changes outside the horizon if the charge mass ratio is closer to each other, unlike in Reissner–Nordström BHs. The angular tidal forces increase infinitely with increase of charge and $\mathrm{\Lambda }$. We derive the geodesic deviation equation on a neutral body for anti-de Sitter torus like charged black hole. We find the radial and angular tidal forces on the neutral body. Furthermore, we express the graphical behavior of radial and angular components for the most suitable initial conditions.

In this paper, we discuss the linearization of vector-spinor (spin-3/2) nonlinear supersymmetry (vsNLSUSY) transformations for both $N=1$ and $N$-extended SUSY in flat spacetime based on the commutator algebra by using functionals (composites) of spin-3/2 Nambu–Goldstone (NG) fermions, which are expressed as simple products of powers of the spin-3/2 NG fermions and a fundamental determinant in the vsNLSUSY theory. We define basic component fields by means of those functionals in a linearized vsSUSY theory including spin-3/2 fields, general auxiliary ones and a $D$-term. The general forms of linear (rigid) vsSUSY transformations for the component fields are determined uniquely from the commutator-based linearization procedure. By considering appropriate recombinations of the functionals of the spin-3/2 NG fermions for $N=1$ SUSY, we find that variations of the recombinations under the vsNLSUSY transformations include linear spin-1/2 SUSY ones of spin-$(3/2,1)$ fields with $U(1)$ gauge invariance. The spinorial gauge invariance of the Rarita–Schwinger action in the linearization process is also discussed together with the $U(1)$ gauge invariance.

In this paper, we study topological defect lines in two character rational conformal field theories. Among them one set of two character theories are commutant pairs in $E_{8,1}$ conformal field theory. Using these defect lines, we construct defect partition function in the $E_8$ theory. We find that the defects preserve only a part of the $E_8$ current algebra symmetry. We also determine the defect partition function in $c=24$ CFTs using these defects lines of two character theories and we find that, with appropriate choice of commutant pairs, these defects preserve all current algebra symmetries of $c=24$ CFTs.