  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 \Lambda^2 V^* \otimes 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.
