  The effective action for the interacting massive scalar field in curved
space-time is derived using the heat-kernel method. Starting from this
effective action, we establish a smooth quadratic form of the low-energy
decoupling for the four-scalar coupling constant and for the nonminimal
interaction parameter. The evolution of this parameter from the conformal value
1/6 at high energies down to the IR regime is investigated within the two toy
models with negative and positive four-scalar coupling constants.
