Torsten Ekedahl

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Torsten Ekedahl, Sergei Lando, Michael Shapiro, and Alek Vainshtein ∗ Dept. of Math., University of Stockholm, S-10691, Stockholm, teke@matematik.su.se † Higher College of Math., Independent University of Moscow, and Institute for System Research RAS, lando@mccme.ru ‡ Department of Mathematics, Royal Institute of Technology, S-10044, Stockholm,(More)
The enumeration of points on (or off) the union of some linear or affine subspaces over a finite field is dealt with in combinatorics via the characteristic polynomial and in algebraic geometry via the zeta function. We discuss the basic relations between these two points of view. Counting points is also related to the l-adic cohomology of the arrangement(More)
We introduce a stratification on the space of symplectic flags on the de Rham bundle of the universal principally polarised abelian variety in positive characteristic and study its geometric properties like irreducibility of the strata and we calculate the cycle classes. When the characteristic p is treated as a formal variable these classes can be seen as(More)
— We show that, if a meromorphic function of degree at most four on a real algebraic curve of an arbitrary genus has only real critical points, then it is conjugate to a real meromorphic function by a suitable projective automorphism of the image. Résumé. — On montre que, si tous les points critiques d’une fonction méromorphe de degré au plus quatre sur une(More)
We give an explicit construction, for a flat map X → S of algebraic spaces, of an ideal in the n’th symmetric product of X over S. Blowing up this ideal is then shown to be isomorphic to the schematic closure in the Hilbert scheme of length n subschemes of the locus of n distinct points. This generalises Haiman’s corresponding result ([13]) for the affine(More)
∗ Dept. of Math., University of Stockholm, S-10691, Stockholm, teke@matematik.su.se † Higher College of Math., Independent University of Moscow, and Institute for System Research RAS, lando@mccme.ru ‡ Department of Mathematics, Royal Institute of Technology, S-10044, Stockholm, mshapiro@math.kth.se ♮ Dept. of Math. and Dept. of Computer Science, University(More)