Séminaires : Séminaire Théorie des Nombres

Equipe(s) : tn,
Responsables :Ziyang Gao, Marc Hindry, Bruno Kahn, João Pedro P. dos Santos
Email des responsables : ziyang.gao@imj-prg.fr
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Orateur(s) S. Keel - ,
Titre Towards the ample cone of $\overline{M}_{g,n}$
Date21/05/2001
Horaire14:00 à 16:00
RésumeThere are a natural collection of rational curves (deep) in theboundary of $\overline{M}_{g,n}$, the so called 1-strata, theirreducible components of the locus of (pointed) curves with at least3g-3 +n -1 singular points. Together with Gibney and Morrison, Iconjecture that a divisor is ample iff it has positive intersectionwith each of these curves, and moreover, in char p, that a divisor issemi-ample (ie. the linear system of some positive multiple is freeof base-points) iff it has non-negative intersection with each ofthese curves. I'll explain our main result, which is that theconjecture holds in general iff it holds for $g=0$, and strongevidence for the $g=0$ case.
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