  It is shown, using quantum field theory in curved spacetime, how the
expansion of the universe during inflation produces an aggregate of particles
and inflaton vacuum fluctuations at a temperature of 5x10^17GeV and dense
enough to make reheating unnecessary. The standard calculation that predicts
the Hubble parameter has to be way smaller than the Planck energy is shown to
be fallacious: it applies the conservation of the perturbative curvature R to a
single inflaton fluctuation when it should be applied to the energy density
contrast of an aggregate. The quantum inflaton fluctuations varphi are with
respect to the classical value phi_0 of the inflaton field phi=phi_0+varphi.
Fluctuations varphi that have grown to the size of the horizon, or a pair of
virtual particles that are separated by a distance the length of the horizon,
are forced to become real and take energy from the potential V(phi_0). The
slowing down of inflation is due to the eventual domination of the continuously
being created radiation over the decreasing inflaton potential V(phi_0). It is
not necessary at all for the potential V(phi_0) to go to zero. Since there is
no need for reheating the inflaton field phi does not couple to matter (except
gravitationally). After inflation, the fluctuations varphi quickly cool down
and can be described as dark matter. Now the inverse process begins to occur.
Inflaton fluctuations varphi that exited the horizon during inflation begin
reentering it after inflation's end. Then they are again causally connected and
have a probability of undergoing the inverse of the quantum process they
underwent before and give their energy back to the potential V(phi_0). The
varphi fluctuations are turning into V(phi_0), which acts as dark energy and
accelerates again the expansion of the universe. The disintegration of a
perturbation is a quantum jump of cosmological size.
