Séminaire de Géométrie Tropicale

Institut Mathématiques de Jussieu ,
Université Pierre et Marie Curie, Paris 6
UMR CNRS 7586



Mercredi 27 mars, 10h30 salle 1525-502



Federico Ardila (San Francisco State University)

Double Hurwitz numbers as splines

Résumé :
The Double Hurwitz number H_d_g(mu,nu) counts the genus g, degree d covers of P1 which have ramification profiles mu and nu at 0 and infinity, and simple ramification elsewhere. By thinking of double Hurwitz numbers as splines, we prove several results about their rich combinatorial structure. Two important tools are Cavalieri-Johnson-Markwig's tropical approach to Hurwitz numbers and De Concini-Procesi-Vergne's algebraic-combinatorial approach to the index of transversally elliptic operators. algebraic-combinatorial approach to the index of transversally elliptic operators.