Search

We analyze the electromagnetic-gravity interaction in a pure Hořava-Lifshitz framework. To do so we formulate the Hořava-Lifshitz gravity in 4+1 dimensions and perform a Kaluza-Klein reduction to 3+1 dimensions. We use this reduction as a mathematical procedure to obtain the 3+1 coupled theory, which at the end is considered as a fundamental, self-consistent theory. The critical value of the dimensionless coupling constant in the kinetic term of the action is λ=1/4. It is the kinetic conformal point for the nonrelativistic electromagnetic-gravity interaction. In distinction, the corresponding kinetic conformal value for pure Hořava-Lifshitz gravity in 3+1 dimensions is λ=1/3. We analyze the geometrical structure of the critical and noncritical cases, they correspond to different theories. The physical degrees of freedom propagated by the noncritical theory are the transverse traceless graviton, the transverse gauge vector and two scalar fields. In the critical theory one of the scalars is absent, only the dilaton scalar field is present. The gravity and vector excitations propagate with the same speed, which at low energy can be taken to be the speed of light. The field equations for the gauge vector in the nonrelativistic theory have exactly the same form as the relativistic electromagnetic field equations arising from the Kaluza-Klein reduction of general relativity, and are equal to them for a particular value of one of the coupling constants. The potential in the Hamiltonian is a polynomial of finite degree in the gauge vector and its covariant derivatives. [ABSTRACT FROM AUTHOR]

The present work is focused on the investigation of the existence of compact structures describing anisotropic matter distributions within the framework of modified gravity theories, specifically f(R,T) gravity theory. Additionally, we have taken f(R,T) as a linear function of the Ricci scalar R and the trace of the energy-momentum tensor T as f(R,T)=R+2χT, where χ is a dimensionless coupling parameter, and the Lagrangian matter Lm=-1/3(2pt+pr), to describe the complete set of field equations for the anisotropic matter distribution. We follow the embedding class I procedure using the Eisland condition to obtain a full space-time description inside the stellar configuration. Once the space-time geometry is specified, we determine the complete solution of modified Einstein equations by using the MIT bag model equation of state pr=1/3(ρ-4B) that describes the strange quark matter (SQM) distribution inside the stellar system, where B denotes a bag constant. The physical validity of our anisotropic solution is confirmed by executing several physical tests. It is worth mentioning that with the help of the observed mass values for the various strange star candidates, we have predicted the exact radii by taking different values for χ and B. These predicted radii show a monotonic decreasing nature as the parameter χ is moved from -0.8 to 0.8 progressively. In this case, our anisotropic stellar system becomes more massive and transforms into more dense compact stars. We also perform a detailed graphical analysis of the compact star. As a result, for χ<0, the current modified f(R,T) gravity seems promising to explain the observed massive compact astrophysical objects, similar to magnetars, massive pulsars, and Chandrasekhar super white dwarfs, which are not justified in the framework of general relativity. Finally, we note that when χ=0, general relativity results for anisotropic matter distributions are recovered. [ABSTRACT FROM AUTHOR]