IMPROVING THE RECONSTRUCTION OF THE VELOCITY POTENTIAL AND PRIMORDIALDENSITY-FLUCTUATIONS BY CHOICE OF SMOOTHING WINDOWS

Recently considerable attention has been focused on improving algorith ms for restoring primordial density fluctuations in the universe or in vestigating large-scale velocity fields by going to higher order appro ximations relating nonlinear states to their initial conditions. An al ternative approach is to investigate the use of alternative smoothing windows within the context of first-order approximations. I present ev idence that the universally used Gaussian smoothing window is far from optimal. A sharp truncation P(k) = 0 for k > k(c) leads to a much mor e direct connection to initial conditions for either ''Gaussianization '' methods or use of the Zel'dovich approximation, as discussed in the text.