Decay of the vacuum energy into cosmic microwave background photons

We examine the possibility of the decay of the vacuum energy into a homogeneous distribution of a thermalized cosmic microwave background (CMB), which is characteristic of an adiabatic vacuum energy decay into photons. It is shown that observations of the primordial density fluctuation spectrum, obtained from CMB and galaxy distribution data, restrict the possible decay rate. When photon creation due to an adiabatic vacuum energy decay takes place, the standard linear temperature dependence T(z) = T-0(1 + z) is modified, where To is the present CMB temperature, and can be parametrized by a modified CMB temperature dependence (T) over bar (z) = T-0(1 + z)(1-beta). From the observed CMB and galaxy distribution data, a strong limit on the maximum value of the decay rate is obtained by placing a maximum value beta max similar or equal to 3.4 x 10(-3) on the beta parameter.