Inflaton and spinodal instability

Motivated by results in exact renormalization group studies, we consider an inflaton model with non-minimal coupling, leading to a potential which evolves with the curvature scalar of the Universe, in a similar way a coarse grained potential evolves with the energy scale. Starting with a symmetry breaking feature, the evolution of the effective potential mimics a Wilsonian flow in energy, and flattens as the Universe expands, providing an effective description of quantum corrections dressing the system. The resulting scenario describes first a de Sitter phase, where the inflaton potential is static, followed by a preheating period during which the potential becomes flat, quickly enough for the inflaton never to reach the minimum of the bare potential.