Cosmological implications of Rastall-$f(R)$ theory

TL;DR

This paper explores a generalized Rastall-$f(R)$ gravity model's cosmological implications, fitting it to observational data, and analyzing its dynamical behavior to show it can predict a more accelerated universe than the standard $ ext{ extLambda}$CDM model.

Contribution

It introduces a generalized Rastall-$f(R)$ theory with arbitrary Ricci scalar functions, fits model parameters to data, and analyzes its dynamical properties and acceleration predictions.

Findings

The model fits observational $H_0$ and $f\sigma_8$ data.

For $\eta \in (0,1)$, the dust-dominated fixed point is lost.

The theory predicts a more accelerating universe than $\Lambda$CDM.

Abstract

Cosmological implications of a generalized Rastall theory where the non-conservation equation is promoted to accepts arbitrary functions of the Ricci scalar is considered. We have obtain the model parameters of the power-law ansatz $f\propto R^\eta$, using $H_0$ and $f\sigma_8$ data sets and show that the generalized Rastall theory could satisfy observational data. The dynamical analysis of the model shows that for $\eta\in(0,1)$, the dust dominated fixed point is lost and as a result the parameter range of $\eta$ should be restricted to $\eta\geq1$. We will also show that the genralized Rastall theory will predict more accelerating universe with larger radius, compared to the $\Lambda$CDM model.