Discrete CATS Seminar
U N I V E R S I T Y   O F   K E N T U C K Y
WHERE CATS =
845 PATTERSON OFFICE TOWER
2008 - 2009
"The cd-index of Bruhat and balanced graphs"
Margaret A. Readdy
University of Kentucky
Monday, January 26, 2009
4:00 pm, 845 Patterson Office Tower
The cd-index is a noncommutative polynomial which compactly encodes
the flag vector data of an Eulerian poset. There is a simple yet
powerful coalgebraic structure on the cd-index which enables one to
understand how the cd-index of a polytope changes under geometric
operations and prove non-trivial inequalities among the face incidence
Billera and Brenti have recently developed the notion of the
"complete" cd-index for Bruhat graphs. Although maximal chains in the
Bruhat graph are not all the same length, one can nevertheless define
an extended cd-index. Motivated by their work, we consider a more
general class of labeled graphs which satisfy a balanced condition and
develop the cd-index.
This is joint work-in-progress with Richard Ehrenborg.