Discrete CATS Seminar
U N I V E R S I T Y
K E N T U C K Y
WHERE CATS =
845 PATTERSON OFFICE TOWER
"An Eulerian poset that lacks an R-labeling"
University of Kentucky
Monday, October 5, 2009
4:00 pm, 845 Patterson Office Tower
The original notion of an R-labeling of a poset, due to Bjorner and
Stanley, uses a linearly ordered set for the labels. Bjorner and Wachs
extended this notion to when the label set has a partial order. We
take the next natural step and let the set of labels just have a
relation on it. We then reformulate the notion of R-labeling to triple
assignment. We obtain a structure theorem for triple assignments on
the butterfly poset. Using this we construct an Eulerian poset that
has a positive flag h-vector but does not have any R-labeling. We end
with many open questions.
This is joint work with Margaret Readdy.