On Cohen-Macaulay posets of dimension two and permutation graphs

Abstract

We characterize Cohen-Macaulay posets of dimension two; they are precisely the shellable and strongly connected posets of dimension two. We also give a combinatorial description of these posets. Using the fact that co-comparability graph of a 2-dimensional poset is a permutation graph, we characterize Cohen-Macaulay permutation graphs.

arXiv comment7 pages. Comments are welcome