We show that the stellar subdivisions of a simplex are extendably shellable. These polytopes appear as the facets of the dual of a hypersimplex. Using this fact, we calculate the simplicial and toric h-vector of the dual of a hypersimplex. Finally, we calculate the contribution of each shelling component to the toric h-vector.

We prove the equivalence of EL-shellability and existence recursive atom ordering independent roots. show that a comodernistic lattice, as defined by Schweig Woodroofe, admits roots, therefore is EL-shellable. also present discuss simpler EL-shelling on one most important classes order congruence lattices.

We exhibit a canonical connection between maximal (0, 1)-fillings of a moon polyomino avoiding north-east chains of a given length and reduced pipe dreams of a certain permutation. Following this approach we show that the simplicial complex of such maximal fillings is a vertex-decomposable, and thus shellable, sphere. In particular, this implies a positivity result for Schubert polynomials. Mor...

In this paper we study the partially ordered set of the involutions of the symmetric group Sn with the order induced by the Bruhat order of Sn . We prove that this is a graded poset, with rank function given by the average of the number of inversions and the number of excedances, and that it is lexicographically shellable, hence Cohen-Macaulay, and Eulerian.

We show that Ding's partial order on maximal rook placements on any Ferrers board has a symmetric chain decomposition and is EL-shellable. As a consequence the partial order is Peck, and we show that it has Mobius function values of 1; 0 or +1.