Showing papers by "Norbert Sauer published in 2002"
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TL;DR: It is shown that infinite chordal graphs, even of diameter two, need not be cop-win and point to some interesting questions, some of which are answered.
35 citations
TL;DR: This paper completely describes the vertex partition property HT, which is the property of countable homogeneous directed graph which does not embed any of the tournaments in T.
9 citations
TL;DR: It is proved that if A and B are connected graphs, each containing a triangle and if G is a -free graph with and , then G is the graph that is -free if and only if both a and c are adjacent to b and d.
Abstract: Given two graphs A and G, we write if there is a homomorphism of A to G and if there is no such homomorphism. The graph G is -free if, whenever both a and c are adjacent to b and d, then a = c or b = d. We will prove that if A and B are connected graphs, each containing a triangle and if G is a -free graph with and , then (here "
" denotes the categorical product).
6 citations
Journal Article•
TL;DR: By introducing a new operation, the exponentiation of formal languages, it turns out that some well known families of languages are closed under this exponentiation, e.
Abstract: By introducing a new operation, the exponentiation of formal languages, we can define Heyting algebras of formal languages. It turns out that some well known families of languages are closed under this exponentiation, e. g., the families of regular and of context-sensitive languages.
2 citations