Rutgers Discrete Mathematics Seminar

Title: Euler Enumeration

Speaker: Margaret A. Readdy, Princeton University and University of Kentucky

Date: Monday, March 9, 2015 11:00 am

Location: CoRE Bldg, Room 431, Rutgers University, Busch Campus, Piscataway, NJ


The flag vector contains all the face incidence data of a polytope, and in the poset setting, the chain enumerative data. It is a classical result that for face lattices of polytopes, and more generally, Eulerian graded posets, the flag vector can be written as a cd-index, a non-commutative polynomial which removes all the linear redundancies among the flag vector entries. This holds for regular CW complexes. We relax the regularity conditions to show the cd-index exists for manifolds whose boundary has a Whitney stratification. We also indicate how the setting of Whitney stratifications expands the nature of questions in the area of flag enumeration.

No prior knowledge of polytopes, topology, etc. will be assumed. The only prerequisite is knowing how to count.

This is joint work with Richard Ehrenborg and Mark Goresky