HINTS OF DYNAMICAL VACUUM ENERGY IN THE EXPANDING UNIVERSE

Recently there have been claims of model-independent evidence of dynamical dark energy. Herein we consider a fairly general class of cosmological models with a time-evolving cosmological term of the form Lambda(H) = C-0 + CHH2 + C-(H) over dot(H) over dot. where H is the Hubble rate. These models are well motivated from the theoretical point of view since they can be related to the general form of the effective action of quantum field theory in curved spacetime. Consistency with matter conservation can be achieved by letting the Newtonian coupling G change very slowly with the expansion. We solve these dynamical vacuum models and fit them to the wealth of expansion history and linear structure formation data. The results of our analysis indicate a significantly better agreement as compared to the concordance Lambda CDM model, thus supporting the possibility of a dynamical cosmic vacuum.