Bias in matter power spectra?

We review the constraints given by the linear matter power spectra data on cosmological and bias parameters, comparing the data from the PSCz survey ( Hamilton et al. 2000) and from the matter power spectrum infered by the stu dy of Lyman alpha spectra at z = 2.72 (Croft et al. 2000). We consider flat -Lambda cosmologies, allowing Lambda, H-0 and n to vary, and we also let th e two ratio factors r(pscz) and r(Lyman) (r(i)(2) = P-i(k)/P-CMB(k)) vary i ndependently. Using a simple chi (2) minimisation technique, we find confid ence intervals on our parameters for each dataset and for a combined analys is. Letting the 5 parameters vary freely gives almost no constraints on cos mology, but the requirement of a universal ratio for both datasets implies unacceptably low values of H-0 and Lambda. Adding some reasonable priors on the cosmological parameters demonstrates that the power derived by the PSC z survey is higher by a factor of similar to1.75 compared to the power from the Lyman alpha forest survey.