We study solutions for the Klein–Gordon equation with vector and scalar potentials of the Coulomb types under the influence of noninertial effects in the cosmic string spacetime. We also investigate a

The possibility of modifications on general relativity is investigated. We propose an alternative theory of gravity constructed with the combination of Rastall and rainbow theories. The hydrostatic equilibrium equations are obtained in order to test the new theory in neutron stars, whose mass-radius diagrams are obtained using modern equations of state of nuclear matter derived from relativistic mean field models and compared with the ones computed by the Tolman-Oppenheimer-Volkoff equations. Different sets of parameters are used and the obtained results confronted with accepted masses and radii values, including important astrophysical objects as the quiescent LMXB NGC 6397 and the double neutron system J0737. We conclude that substantial modifications are obtained even for very small alterations on the two free parameters, making the reproduction of astrophysical observations an easier task.

In this paper we present two different classes of solutions for the Klein–Gordon equation in the presence of a scalar potential under the influence of noninertial effects in the cosmic string spacetime. We show that noninertial effects restrict the physical region of the spacetime where the particle can be placed, and furthermore that the energy levels are shifted by these effects. In addition, we show that the presence of a Coulomb-like scalar potential allows the formation of bound states when the Klein–Gordon equation is considered in this kind of spacetime.

A relativistic wave equation for spin 1/2 particles in the Melvin space-time, a space-time where the metric is determined by a magnetic field, is obtained. The energy levels for these particles are...

In this work, we investigate anisotropic effects on the equations of state (EoS) used to describe neutron and quark stars in the framework of Rastall–Rainbow gravity. All our calculations are computed using two different EoS to describe the matter contained within the star: the MIT bag model for quark stars and the IU-FSU parameterisation for the standard hadronic matter. From the values of masses and radii obtained, we can conclude that anisotropic pressure has significant consequences on the structure of compact objects. Specifically, when anisotropy is considered within general relativity, it significantly modifies the maximum stellar mass. On the other hand, when Rastall–Rainbow gravity and anisotropy are simultaneously considered, they provide the best results for the masses and radii of some important astrophysical objects such as the low-mass x-ray binary (LMXB) NGC 6397 and the extremely massive millisecond pulsating source of radio (PSR) J0740 + 6620, for instance. Radii results inferred from the Lead Radius EXperiment (PREX-2) and the compact object in the mass-gap of GW190814 event can also be described for certain values of the Rastall–Rainbow and anisotropy parameters.