Presently decaying dark energy?

Abstract

Investigation of dark energy (DE) properties using the largest existing Constitution supernovae sample including recent CfA data for small redshifts and omitting the assumption of a constant equation of state w for DE reveals a slight inconsistency (more than 1σ) with the standard spatially flat LCDM model. The effect which is most clearly seen using the recently introduced Om diagnostic corresponds to an increase of both this diagnostic and w at redshifts z<∼ 0.3. Interestingly, such DE behaviour produces a better fit to baryon acoustic oscillation data too. Including the cosmic microwave background shift parameter as another independent observation, we have shown that the well known CPL parametrization is not suitable to fit the data at low and high redshifts simultaneously because of this non-trivial DE behaviour implied by them. If not systematic, this effect would correspond to DE decaying into dark matter or something else presently, and we have found good consistency of a toy model for this process with the data.