Strong limits on the possible decay of the vacuum energy into CDM or CMB photons

We investigate models that suggest that the vacuum energy could decay into cold dark matter (CDM) or into a homogeneous distribution of thermalized cosmic microwave background (CMB) photons. We show that the agreement of the density fluctuation spectra obtained from the CMB and galaxy distribution data puts strong limits on the rate of vacuum energy decay. A vacuum energy decaying into CDM increases the density of the CDM rho, diluting the CDM density fluctuations (dr/rho)². The temperature fluctuations of the CMB photons (deltaT/T)² are approximately proportional to...