Observational Consequences of Dark Energy Decay

We consider the generic scenario of dark energy which arises through the latent heat of a hidden sector first order cosmological phase transition. This field could account for the extra radiation degree of freedom suggested by the CMB. We present the bubble nucleation solution for the viscous limit. The decay rate of the field is constrained by published KSZ data, and may be an explanation of current excess ISW correlations. Cross correlation of current and future surveys can further constrain or test the parameter space. The decay model is plausibly in the observable range, and avoids anthropic problems. This class of models is not well constrained by the popular dark energy figure of merit.