angewandte Mathematik © Walter de Gruyter

Projective normality and syzygies of algebraic surfaces Dedicated to David Eisenbud on his fiftieth birthday By F. J. Gal lego1) at Madrid and B. P. Purnaprajna at Lawrence Abstract. In this work we develop new techniques to compute Koszul cohomology groups for several classes of varieties. As applications we prove results on projective normality and syzygies for algebraic surfaces. From more general results we obtain in particular the following: (a) Mukai 's conjecture (and stronger variants of it) regarding projective normality and normal presentation for surfaces with Kodaira dimension 0, and uniform bounds for higher syzygies associated to adjoint linear series, (b) effective bounds along the lines of Mukai's conjecture regarding projective nor-mality and normal presentation for surfaces of positive Kodaira dimension, and, (c) results on projective normality for pluricanonical models of surfaces of general type (recovering and strengthening results by Ciliberto) and generalizations of them to higher syzygies. In addition, we also extend the above results to singular surfaces