  Suppose that the early Universe starts with a cosmological $\Lambda$-term
originating from quantum spacetime at the Planck scale. Dark energy drives
inflation and reheating by reducing its value for massive particle-antiparticle
pairs production and oscillation, resulting in a holographic and massive pair
plasma state. The back-and-forth reaction of dark energy and massive pairs
slows inflation to its end and starts reheating by rapidly producing stable and
unstable pairs. We introduce the Boltzmann-type rate equation describing the
back-and-forth reaction. It forms a close set with Friedman equations and
reheating equations for unstable pairs decay to relativistic particles. The
numerical solutions show preheating, massive pairs dominated and genuine
reheating episodes. We obtain the reheating temperature and entropy in terms of
the tensor-to-scalar ratio $0 < r < 0.047$ consistently with observations.
Stable massive pairs represent cold dark matter particles and weakly interact
with dark energy. The resultant cold dark matter abundance $\Omega_c\sim
10^{-1}$ is about a constant in time.
