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119048Moscow, Usacheva str., 6
phone/fax: +7 (495) 624-26-16
phone: +7 (495) 916-89-05
e-mail: math@hse.ru
Organizers: Alexander Esterov esterov@gmail.com, Valentina Kiritchenko vkiritchenko@yahoo.ca
Announcement: Alexander Esterov "Spherical characteristic classes", Oct. 17, 2013, room 302
Abstract: "Spherical characteristic classes" are defined for (not necessarily compact or regular) subvarieties in a spherical homogeneous space,
and take values in the ring of conditions of the ambient space (as defined by de Concini and Procesi).
A special case that will be of primary interest for me is the "tropical characteristic class" of a subvariety of a complex torus.
I will explain how to prove its existence constructively,
how to deduce known facts about Newton polytopes from basic properties of tropical characteristic classes
(for instance, how to prove Kouchnirenko-Bernstein-Khovanskii theorem in two lines),
how tropical characteristic classes are related to Schwarz-MacPherson classes,
and how they lead to a new approach to Mikhalkin-type tropical correspondence theorems in enumerative geometry.
Program:
Patchworking (1st module): Introduction to real algebraic geometry, Harnack's curve inequality, Viro's patchworking, moment maps, ℝ+-toric varieties, proof of the patchworking theorem.
Toric varieties (2nd module): polytopes, fans and toric varieties; convex-algebro-geometric dictionary; Kouchnirenko theorem; mixed volumes; Bernstein theorem; Dehn–Sommerville equations.
Tropical geometry (3rd-4th module): tropical algebra, amoebas, tropical Bezout theorem, introduction to enumerative geometry, Mikhalkin's tropical correspondence theorem, sparse resultants and A-discriminants, secondary polytope, proof of Mikhalkin's theorem for 1 and 2 nodes, outline for the general case.
Reading:
Viro's textbooks (http://www.pdmi.ras.ru/~olegviro/educ-texts.html)
Textbooks and works by Kouchnirenko, Bernstein, Khovanskii and Timorin at http://math.hse.ru/nis-12-vgeom
I. Itenberg, G. Mikhalkin, E. Shustin. Tropical algebraic geometry. http://books.google.fr/books?id=4JP7ofjHVh8C
M. Kazarian. Tropical geometry. http://www.mccme.ru/dubna/2006/notes/Kazaryan.pdf