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We show that inflation and current cosmic acceleration can be generated by a metric-affine f (R) gravity formulated in the Einstein conformal frame, if the gravitational Lagrangian L (R) contains both positive and negative powers of the curvature scalar R. In this frame, we give the equations for the expansion of the homogeneous and isotropic matter-dominated universe in the case L (R) =R+R³/β²-α²/3R, where αand βare constants. We also show that gravitational effects of matter in such a universe at very late stages of its expansion are weakened by a factor that tends to 3/4, and the energy density of matter εscales the same way as in the Λ-CDM model only when κ*ε<
Nikodem J. Popławski (Tue,) studied this question.