Reheating of the universe after inflation with f(phi)R gravity

We show that reheating of the universe occurs spontaneously in a broad class of inflation models with $f(\phi)R$ gravity ($\phi$ is inflaton). The model does not require explicit couplings between $\phi$ and bosonic or fermionic matter fields. The couplings arise spontaneously when $\phi$ settles in the vacuum expectation value (vev) and oscillates, with coupling constants given by derivatives of $f(\phi)$ at the vev and the mass of resulting bosonic or fermionic fields. This mechanism allows inflaton quanta to decay into any fields which are not conformally invariant in $f(\phi)R$ gravity theories.