Compositio Mathematica

The cd-index of fans and posets

Kalle Karu a1
a1 Mathematics Department, University of British Columbia, 1984 Mathematics Road, Vancouver, BC, Canada V6T 1Z2

Article author query
karu k   [Google Scholar] 


The number of flags in a complete fan, or more generally in an Eulerian poset, is encoded in the cd-index. We prove the non-negativity of the cd-index for complete fans, regular CW-spheres and Gorenstein* posets.

(Published Online May 17 2006)
(Received May 18 2005)
(Accepted September 16 2005)

Key Words: cd-index; flag h-vector; Gorenstein* posets.

Maths Classification

14M25 (primary); 06A07 (secondary).