2002/03/18 by Yves Laszlo, Laszlo, Yves, Christian Pauly +1 · 1 citation
Mathematics · #Algebraic Geometry (math.AG) #FOS: Mathematics #math.AG
paper · pdf · doi:10.48550/arxiv.math/0203175
17 pages
arxiv created 2002/03/18 · arxiv updated 2009/11/30
Let X be a smooth projective curve of genus g>1 defined over an algebraically closed field k of characteristic p>0. Let MX(r) be the moduli space of semi-stable rank r vector bundles with fixed trivial determinant. The relative Frobenius map F : X → X1 induces by pull-back a rational map V: MX1(r) → MX(r). We determine the equations of V in the following two cases (1) (g,r,p) = (2,2,2) and X non-ordinary with Hasse-Witt invariant equal to 1 (see math.AG/0005044 for the case X ordinary), and (2) (g,r,p) = (2,2,3). We also show, for any triple (g,r,p), the existence of base points of V, i.e., semi-stable bundles E such that F^* E is not semi-stable.