Ysystems and generalized associahedra IISergey FominUniversity of Michigan
February 22,

ABSTRACT


This is the second of two talks based on a joint paper The presentation will be selfcontained, and will focus on the second part of the title ("generalized associahedra"). We introduce and study a family of simplicial complexes which can be viewed as a generalization of the Stasheff polytope (a.k.a. associahedron) for an arbitrary root system. In types A and B, our construction recovers, respectively, the ordinary associahedron and the BottTaubes polytope, or cyclohedron. In a followup joint project with Frederic Chapoton, we present explicit polytopal realizations of these generalized associahedra. On the enumerative side, these constructions provide natural root system analogues to noncrossing/nonnesting partitions. 
Combinatorics Seminar, Mathematics Department, MIT, sara(atsign)math.mit.edu 

