  Massive particle and antiparticle pair production and oscillation on the
horizon form a holographic and massive pair plasma state in the Friedman
Universe. Via this state, the Einstein cosmology term (dark energy) interacts
with matter and radiation and is time-varying $\tilde\Lambda$ in the Universe's
evolution. It is determined by a close set of ordinary differential equations
for dark energy, matter, and radiation energy densities. The solutions are
unique, provided the initial conditions given by observations. In inflation and
reheating, dark energy density decreases from the inflation scale, converting
to matter and radiation energy densities. In standard cosmology, matter and
radiation energy densities convert to dark energy density, reaching the present
Universe. By comparing with $\Lambda$CDM, quintessence and dark energy
interacting models, we show that these results can be the possible solutions
for cosmological fine-tuning and coincidence problems.
