The Starobinsky model within the $f(R,T)$ formalism as a cosmological model

In this paper we derive a cosmological model from the $f(R,T)$ theory of gravity, for which $R$ is the Ricci scalar and $T$ is the trace of the energy-momentum tensor. We consider $f(R,T)=f(R)+f(T)$, with $f(R)$ being the Starobinksy model $R+\alpha R^{2}$ and $f(T)=\gamma T$, with $\alpha$ and $\gamma$ constants. We find that from such a functional form, it is possible to describe the cosmological scenario of a radiation-dominated universe, which has shown to be a non-trivial feature within the $f(R,T)$ formalism.