The search session has expired. Please query the service again.

The search session has expired. Please query the service again.

Previous Page 4

Displaying 61 – 76 of 76

Showing per page

Antichains in the homomorphism order of graphs

Dwight Duffus, Peter, L. Erdös, Jaroslav Nešetřil, Lajos Soukup (2007)

Commentationes Mathematicae Universitatis Carolinae

Let 𝔾 and 𝔻 , respectively, denote the partially ordered sets of homomorphism classes of finite undirected and directed graphs, respectively, both ordered by the homomorphism relation. Order theoretic properties of both have been studied extensively, and have interesting connections to familiar graph properties and parameters. In particular, the notion of a duality is closely related to the idea of splitting a maximal antichain. We construct both splitting and non-splitting infinite maximal antichains...

Associative graph products and their independence, domination and coloring numbers

Richard J. Nowakowski, Douglas F. Rall (1996)

Discussiones Mathematicae Graph Theory

Associative products are defined using a scheme of Imrich & Izbicki [18]. These include the Cartesian, categorical, strong and lexicographic products, as well as others. We examine which product ⊗ and parameter p pairs are multiplicative, that is, p(G⊗H) ≥ p(G)p(H) for all graphs G and H or p(G⊗H) ≤ p(G)p(H) for all graphs G and H. The parameters are related to independence, domination and irredundance. This includes Vizing's conjecture directly, and indirectly the Shannon capacity of a graph...

Atomic compactness for reflexive graphs

Christian Delhommé (1999)

Fundamenta Mathematicae

A first order structure with universe M is atomic compact if every system of atomic formulas with parameters in M is satisfiable in provided each of its finite subsystems is. We consider atomic compactness for the class of reflexive (symmetric) graphs. In particular, we investigate the extent to which “sparse” graphs (i.e. graphs with “few” vertices of “high” degree) are compact with respect to systems of atomic formulas with “few” unknowns, on the one hand, and are pure restrictions of their...

Currently displaying 61 – 76 of 76

Previous Page 4