Growth of cosmic perturbations in the modified $f(R,T)$ gravity

Abstract: We explore the generalized $f(R,T)$ modified theory of gravity, where the gravitational Lagrangian is a function of Ricci scalar $R$ and the trace of the energy-momentum tensor $T$. We derive modified field equations to the linear order of perturbations in the context of $f(R,T)$ model. We then investigate the growth of perturbations in the context of $f(R,T)$ modified gravity. Primary numerical investigations based on matter power spectra diagrams indicate a structure growth suppression in $f(R,T)$ gravity, which exhibits consistency with local measurements. Also, we notice that matter-geometry interaction in $f(R,T)$ model would results in the specific feature named as "matter acoustic oscillations" appeared in matter power spectra diagrams. Moreover, we put constraints on the cosmological parameters of $f(R,T)$ model, utilizing current observations, chiefly cosmic microwave background (CMB), weak lensing, supernovae, baryon acoustic oscillations, and redshift-space distortions data. Numerical results based on MCMC calculations imply that $f(R,T)$ is a qualified theory of modified gravity in reconciling Planck CMB data with local probes of large scale structures, by reporting lower values for the structure growth parameter $\sigma_8$ compared to the standard model of cosmology.