Total nonnegativity and (3+1)-free posets

JOURNAL OF COMBINATORIAL THEORY SERIES A

卷:103

Article

Skandera, M ; Reed, B

关键词: f-vector;    (3+1)-free poset;    unit interval order;    total nonnegativity;    planar network;    generalized lower bound theorem;   

DOI  :  10.1016/S0097-3165(03)00072-4

来源: Elsevier

【 摘 要 】

We factor the squared antiadjacency matrix A(2) of a (3 + 1)-free poset as a product of two antiadjacency matrices of unit interval orders. This gives a new combinatorial interpretation for the entries of A(2) in terms of finite planar networks and a proof that the f-vector of a (3 + 1)-free poset is also the f-vector of a unit interval order. We also state some inequalities satisfied by the components of these f-vectors. (C) 2003 Elsevier Science (USA). All rights reserved.

【 授权许可】

Free