Curves of maximal genus in P^5

Abstract

Let C be a reduced, irreducible, not degenerate curve, not contained on surfaces of degree 3, the bound is stated and proved by Chiantini, Ciliberto and Di Gennaro in 1993. The bound is sharp, at least for d sufficiently large (Chiantini-Ciliberto- Di Gennaro give examples of extremal curves for d large, that are in general singular). The classification and the existence of curves of genus G(d, r, s) is known for r=3 and d>s^2-s (Gruson and Peskine), and for r=4 and d> 12s^2 (Chiantini and Ciliberto in 1994). In this paper the author gives the classification for the curves of maximal genus for r=5, d as in the paper of Chiantini-Ciliberto-Di Gennaro, and s>8, and proves the existence of {\it smooth} curves of maximal genus G(d, 5, s) for every d and s. With the same techniques used for the classification in P^5 it is possible to classify curves in P^r of maximal genus G(d, r, s) for every r and s>2r-2. In math.AG/0105094 the author has given an example of the classification procedure and of the costruction of smooth extremal curves in P^r.