Early dark energy from zero-point quantum fluctuations

Full text: We examine a cosmological model where the dark energy density has the form ρDE(t)=ρX(t)+ρZ(t), where ∂X is the dominant component of dark energy and ρZ(t) is an extra contribution proportional to H2(t). This form of ρZ(t) follows from the recent suggestion that the contribution of zero-point fluctuations of quantum fields to the cosmic expansion is obtained subtracting from the zero-point energy density computed in a FRW space-time the value computed in Minkowski space. Assuming an energy conservation of the form ρX+3H(1|+wX)ρX+ρZ+3H(1+wZ)ρZ=0 we found that, for wZ≠wX, the total dark energy density ρDE(t) always remains a .nite fraction of the critical density at any time, thus providing a simple and appealing solution to the coincidence problem. We compare this model to CMB, supernovae and BAO data. (author)