  The consideration of dark energy's quanta, required also by thermodynamics,
introduces its chemical potential into the cosmological equations. Isolating
its main contribution, we obtain solutions with dark energy decaying to matter
or radiation. When dominant, their energy densities tend asymptotically to a
constant ratio, explaining today's dark energy-dark matter coincidence, and in
agreement with supernova redshift data, and a universe-age constraint. This
also connects the Planck's and today's scales through time. This decay may be
manifested in the highest-energy cosmic rays, recently detected.
