2003/05/15 by William Graham, Graham, William
Mathematics · #14N05 #Advanced Algebra and Geometry #Algebraic Geometry (math.AG) #Algebraic Geometry and Number Theory #Algebraic structures and combinatorial models #FOS: Mathematics #math.AG #msc:14N05
paper · pdf · doi:10.48550/arxiv.math/0305221
13 pages
arxiv created 2003/05/15 · openalex publication_date 2003/05/15 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Let V be a rank N vector bundle on a d-dimensional complex projective scheme X; assume that V is equipped with a skew-symmetric bilinear form with values in a line bundle L and that Λ2 V^* ⊗ L is ample. Suppose that the maximum rank of the form at any point of X is r, where r>0 is even. The main result of this paper is that if d>2(N-r), then the locus of points where the rank of the form is at most r-2 is nonempty. This is a skew-symmetric analogue of the main result of math.AG/0305159; the proof is similar. If the hypothesis of ampleness is relaxed, we obtain a weaker estimate on the maximum dimension of X (and give a similar result for the symmetric case). We give applications to subschemes of skew-symmetric matrices, and to the stratification of the dual of a Lie algebra by orbit dimension.