  A constant-rate creation of 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, 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 discuss the cosmological model that arises in
this context and present a joint analysis of observations of the first acoustic
peak in the cosmic microwave background (CMB) anisotropy spectrum, the Hubble
diagram for supernovas of type Ia (SNIa), the distance scale of baryonic
acoustic oscillations (BAO) and the distribution of large scale structures
(LSS). We show that a good concordance is obtained, albeit with a higher value
of the present matter abundance than in the standard model.

Cosmology and Nongalactic Astrophysics;General Relativity and Quantum Cosmology;High Energy Physics - Theory