  We study a scalar phi field that unifies inflation and dark energy with a
long period of a hot decelerating universe in between these two stages of
inflation. A key feature is that the transition between the intermediate
decelerated phase to the dark energy phase is related to a quantum regeneration
of the scalar field phi instead to purely classical dynamics. The interaction
V_int(phi,varphi) between phi and a second scalar field varphi allows not only
for phi to decay at a high energy E_I, even though phi does not oscillate
around the minimum of its potential, but it also regenerates phi at an energy
E_{BD} \simeq E_I^2 close to present time. It predicts extra relativistic
energy and an interacting dark energy which may account for a w<-1. In the
model presented here we have E_I \simeq 100 TeV and E_{BD} \simeq 1 eV. The low
value of the back decay energy E_{BD} gives an explanation of the coincidence
problem.
