B. S. Gonçalves | Searcharxiv

arXiv2023

Cosmology from non-minimal geometry-matter coupling

We construct a cosmological model from the inception of the Friedmann-Lemâitre-Robertson-Walker metric into the field equations of the f(R,L_m) gravity theory, with R being the Ricci scalar and L_m being the matter lagrangian density. The formalism is developed for a particular f(R,L_m) function, namely R/16π+(1+σR)L_{m}, with σbeing a constant that carries the geometry-matter coupling. Our solutions are remarkably capable of evading the Big-Bang singularity as well as predict the cosmic acceleration with no need for the cosmological constant, but simply as a consequence of the geometry-matter coupling terms in the Friedmann-like equations

gr-qc↗

arXiv2020

Hydrostatic equilibrium configurations of neutron stars in a non-minimal geometry-matter coupling theory of gravity

In this work we analyze hydrostatic equilibrium configurations of neutron stars in a non-minimal geometry-matter coupling (GMC) theory of gravity. We begin with the derivation of the hydrostatic equilibrium equations for the $f(R,L) $ gravity theory, where $R$ and $L$ are the Ricci scalar and Lagrangian of matter, respectively. We assume $f(R,L)=R/2+[1+σR]L$, with $σ$ constant. To describe matter inside neutron stars we assume the polytropic equation of state $p=K ρ^γ$, with $K$ and $γ= 5/3 $ being constants. We show that in this theory it is possible to reach the mass of massive pulsars such as PSR J2215+5135. As a feature of the GMC theory, very compact neutron stars with radius $\sim8$km and $M\sim 2.6M_\odot$ are stable, thus surpassing the Buchdal and Schwarzschild radius limits. Moreover, the referred stellar diameter is obtained within the range of observational data.

gr-qc↗