Even Linkage Classes

In this paper we generalize the and -type resolutions used by Martin-Deschamps and Perrin for curves in to subschemes of pure codimension in projective space, and shows that these resolutions are interchanged by the mapping cone procedure under a simple linkage. Via these resolutions, Rao's correspondence is extended to give a bijection between even linkage classes of subschemes of pure codimension two and stable equivalence classes of reflexive sheaves satisfying and . Further, these resolutions are used to extend the work of Martin-Deschamps and Perrin for Cohen-Macaulay curves in to subschemes of pure codimension two in . In particular, even linkage classes of such subschemes satisfy the Lazarsfeld-Rao property and any minimal subscheme for an even linkage class links directly to a minimal subscheme for the dual class.