Directed graphs and boron trees

JOURNAL OF COMBINATORIAL THEORY SERIES A

卷:132

Article

Sokic, Miodrag

关键词: Ramsey property;    Ordering property;    Expansion property;    Fraisse structures;   

DOI  :  10.1016/j.jcta.2014.12.006

来源: Elsevier

【 摘 要 】

Let L-1 and L-2 be two disjoint relational signatures. Let K-1 and K-2 be Ramsey classes of rigid relational structures in L-1 and L-2 respectively. Let K-1*K-2 be the class of structures in L-1 boolean OR L-2 whose reducts to L-1 and L-2 belong to K-1 and K-2 respectively. We give a condition on K-1 and K-2 which implies that K-1*K-2 is a Ramsey class. This is an extension of a result of M. Bodirsky. In the second part of this paper we consider classes OS(2), OS(3), OB and OH which are obtained by expanding the class of finite dense local orders, the class of finite circular directed graphs, the class of finite boron tree structures, and the class of rooted trees respectively with linear orderings. We calculate Ramsey degrees for objects in these classes (C) 2015 Elsevier Inc. All rights reserved.

【 授权许可】

Free