  The creation of ultra-light dark particles in the late-time FLRW spacetime
provides a cosmological model in accordance with precise observational tests.
The matter creation backreaction implies in this context a vacuum energy
density scaling linearly with the Hubble parameter H, which is consistent with
the vacuum expectation value of the QCD condensate in a low-energy expanding
spacetime. Both the cosmological constant and coincidence problems are
alleviated in this scenario. We also explore the opposite, high energy limit of
the particle creation process. We show that it leads to a non-singular
primordial universe where an early inflationary era takes place, with natural
reheating and exit. The generated primordial spectrum is scale invariant and,
by supposing that inflation lasts for 60 e-folds, we obtain a scalar expectral
index n = 0.97.
