Self-similar cosmological solutions in f(R,T) gravity theory
  We study the $f(R,T)$ cosmological models under the self-similarity
hypothesis. We determine the exact form that each physical and geometrical
quantity may take in order that the Field Equations (FE) admit exact
self-similar solutions through the matter collineation approach. We study two
models: the case$\ f(R,T)=f_{1}(R)+f_{2}(T)$ and the case
$f(R,T)=f_{1}(R)+f_{2} (R)f_{3}(T)$. In each case, we state general theorems
which determine completely the form of the unknown functions $f_{i}$ such that
the field equations admit self-similar solutions. We also state some
corollaries as limiting cases. These results are quite general and valid for
any homogeneous self-similar metric$.$ In this way, we are able to generate new
cosmological scenarios. As examples, we study two cases by finding exact
solutions to these particular models.
