Shellable graphs and sequentially Cohen--Macaulay bipartite graphs

  • Authors:
  • Adam Van Tuyl;Rafael H. Villarreal

  • Affiliations:
  • Department of Mathematical Sciences, Lakehead University, Thunder Bay, ON P7B 5E1, Canada;Departamento de Matemáticas, Centro de Investigación y de Estudios Avanzados del IPN, Apartado Postal 14-740, 07000 Mexico City, DF, Mexico

  • Venue:
  • Journal of Combinatorial Theory Series A
  • Year:
  • 2008

Quantified Score

Hi-index 0.00

Visualization

Abstract

Associated to a simple undirected graph G is a simplicial complex @D"G whose faces correspond to the independent sets of G. We call a graph G shellable if @D"G is a shellable simplicial complex in the non-pure sense of Bjorner-Wachs. We are then interested in determining what families of graphs have the property that G is shellable. We show that all chordal graphs are shellable. Furthermore, we classify all the shellable bipartite graphs; they are precisely the sequentially Cohen-Macaulay bipartite graphs. We also give a recursive procedure to verify if a bipartite graph is shellable. Because shellable implies that the associated Stanley-Reisner ring is sequentially Cohen-Macaulay, our results complement and extend recent work on the problem of determining when the edge ideal of a graph is (sequentially) Cohen-Macaulay. We also give a new proof for a result of Faridi on the sequentially Cohen-Macaulayness of simplicial forests.