  There is some observational evidence for earlier evolution of clusters of
galaxies than predicted in the standard LambdaCDM model with a Gaussian
primordial density fluctuation field, and a low value for the mass variance
parameter sigma_8. Particularly difficult in this model is the interpretation
of possible excess CMB anisotropy on cluster scales as due to the
Sunyaev-Zeldovich (S-Z) effect. We have calculated S-Z power spectra in the
standard model, and in two alternative models which predict higher cluster
abundance - a model with non-Gaussian PDF, and an early dark energy model. As
anticipated, the levels of S-Z power in the latter two models are significantly
higher than in the standard model, and in good agreement with current
measurements of CMB anisotropy at high multipole values. Our results provide a
sufficient basis for testing the viability of the three models by futur high
quality measurements of cluster abundance and the anisotropy induced by the S-Z
effect.
