Flag Vectors of Eulerian Partially Ordered Sets

Margaret M. Bayer, Gábor Hetyei
2001 European journal of combinatorics (Print)  
The closed cone of flag vectors of Eulerian partially ordered sets is studied. A new family of linear inequalities valid for Eulerian flag vectors is given. Half-Eulerian posets are defined. Certain limit posets of Billera and Hetyei are half-Eulerian; they give rise to extreme rays of the cone for Eulerian posets. Other extreme posets are formed from consideration of the cd-index. The cone of Eulerian flag vectors is completely determined up through rank seven.
doi:10.1006/eujc.2000.0414 fatcat:pao7v4tqqrax3fwzzsyb7u2554