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Journal of Lie Theory 17 (2007), No. 1, 163--189 Copyright Heldermann Verlag 2007 Spectral Multipliers on Damek-Ricci Spaces Maria Vallarino Dip. di Matematica e Applicazioni, Università di Milano Bicocca, Via R. Cozzi 53, 20125 Milano, Italy maria.vallarino@unimib.it [Abstract-pdf] Let $S$ be a Damek--Ricci space, and $\Delta$ be a distinguished Laplacean on $S$ which is left invariant and selfadjoint in $L^2(\rho)$. We prove that $S$ is a Calder\'on-Zygmund space with respect to the right Haar measure $\rho$ and the left invariant distance. We give sufficient conditions of H\"ormander type on a multiplier $m$ so that the operator $m(\Delta)$ is bounded on $L^p(\rho)$ when $1
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