Decaying Λ cosmologies and power spectrum

We investigate the evolution of matter density perturbations in a universe with a cosmological term that decreases with time as Λ∝${\mathit{a}}^{\mathrm{-}\mathit{m}}$. For fixed values of ${\mathrm{\Omega }}_{\mathit{m}0}$ the power spectrum is constructed and we show that it is only slightly modified when the parameter m is changed from m=0 to m=2. Some properties concerning the peculiar velocity field are also discussed.