arXiv subjects

Jonas Pinheiro da Silva

Publications and source records attributed to Jonas Pinheiro da Silva.

4 recordsLinked to original sources

arXiv2024

Cosmological eras with the neutrino non-relativistic transition in RTB gravity

Theories based on the Ricci and the trace of the energy-momentum tensor, or the short name Ricci-trace-based (RTB) theories, represent a gravitational approach based on the Ricci scalar $R$, and the trace of the energy-momentum tensor $g^{μν}T_{μν} = T$. This theory fits into gravitational models of the type $f(R, T) = R + f(T)$, where $f(T)$ is an arbitrary function of $T$. In this study, we explore a cosmological scenario within the context of RTB models, investigating in detail the cosmological consequences of the coupling between matter and geometry. In order to address this issue, we propose a toy model in which the non-relativistic cosmological neutrino transition plays a role in the cosmic evolution since the effective total energy-momentum tensor trace is affected in this process. We raise questions about the coupling of neutrinos with geometry during this transition, providing a detailed analysis of how RTB gravity deals with this phenomenon and the impact of neutrinos on cosmological dynamics. In summary, we show that the coupling of cosmological neutrinos with $T$ dependent cosmologies is severely challenged.

gr-qc↗

arXiv2024

Selecting energy-momentum trace dependent gravity theories with LSS

We study scalar cosmological perturbations in $f(R, T)$ modified gravity theories being $T$ the trace of the energy-momentum tensor. We provide detailed equations for the matter energy density contrast. We solve then numerically to promote a comparison with available large scale structure (LSS) formation observational data on $f σ_8$ and also addressing the $S_8$ tension. We identify $f(R,T)$ models that lead either to growth enhancement or suppression. Since recent results in the literature indicate a preference for the latter feature, this type of analysis is quite useful to select viable modifications of gravity. We studied class of such $f(R,T)$ models are either ruled out or severely restricted.

gr-qc↗

arXiv2024

Revisiting $f(R,T)$ cosmologies

We review the status of $f(R,T)$ cosmological models, where $T$ is the trace of the energy momentum tensor $T^{μν}$. We start focusing on the modified Friedmann equations for the minimally coupled gravitational Lagrangian of the type $f(R,T)=R +αe^{βT} + γ_{n} T^{n}$. We show that in such a minimally coupled case there exists a useful constraining relation between the effective fractionary total matter density with an arbitrary equation of state parameter and the modified gravity parameters. With this association the modified gravity sector can be independently constrained using estimations of the gas mass fraction in galaxy clusters. Using cosmological background cosmic chronometers data and demanding the universe is old enough to accommodate the existence of Galactic globular clusters with ages of at least $\sim 14$ Gyrs we find a narrow range of the modified gravity free parameter space in which this class of theories remains viable for the late time cosmological evolution. This preferred parameter space region accommodates the $Λ$CDM limit of $f(R,T)$ models. We also work out the non-minimally coupled case in the metric-affine formalism and find that there are no viable cosmologies in the latter situation. However, when analysing the cosmological dynamics including a radiation component, we find that this energy density interacts with the matter field and it does not scale according to the typical behavior. We conclude stating that $f(R,T)$ gravity is not able to provide a full cosmological scenario and should be ruled out as a modified gravity alternative to the dark energy phenomena.

astro-ph.CO↗

arXiv2023

Modified Kerr-Schild Method applied to Gravity f(R)

We propose an adaptation of the Kerr-Schild method by implementing the correspondence relations (mapping) between Ricci-based Gravity (RBG) and General Relativity (GR). Basically, we generate GR known solutions from a canonical metric with a well-defined form and then obtain the configuration of this solution for the Gravity f(R). The new method allows us to perturb the metric associated with GR with a null geodetic vector, but instead of taking us to a new solution described by Einstein's gravitational sector, it allows us to configure this solution in an RBG.

gr-qc↗