f(R) gravity model for dark energy and dark matter

In this paper, we suggest an f(R) gravity model for the dark energy, which can also be applied for a kind of galactic dark matter. Constructing the f(R) gravitational Lagrangians by Legendre transform from scalar-tensor theories, we study a future behavior of the late-time accelerating Universe as well as a subsequent behavior of an inflation model. Moreover, we discuss possible relations to the galactic dark matter, with a spherically symmetric solution for the static metric in our f(R) model.