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Domination numbers in graphs with removed edge or set of edges

Magdalena Lemańska (2005)

Discussiones Mathematicae Graph Theory

It is known that the removal of an edge from a graph G cannot decrease a domination number γ(G) and can increase it by at most one. Thus we can write that γ(G) ≤ γ(G-e) ≤ γ(G)+1 when an arbitrary edge e is removed. Here we present similar inequalities for the weakly connected domination number γ w and the connected domination number γ c , i.e., we show that γ w ( G ) γ w ( G - e ) γ w ( G ) + 1 and γ c ( G ) γ c ( G - e ) γ c ( G ) + 2 if G and G-e are connected. Additionally we show that γ w ( G ) γ w ( G - E ) γ w ( G ) + p - 1 and γ c ( G ) γ c ( G - E ) γ c ( G ) + 2 p - 2 if G and G - Eₚ are connected and Eₚ = E(Hₚ) where Hₚ of order p is a connected...

Edge-disjoint paths in permutation graphs

C. P. Gopalakrishnan, C. Pandu Rangan (1995)

Discussiones Mathematicae Graph Theory

In this paper we consider the following problem. Given an undirected graph G = (V,E) and vertices s₁,t₁;s₂,t₂, the problem is to determine whether or not G admits two edge-disjoint paths P₁ and P₂ connecting s₁ with t₁ and s₂ with t₂, respectively. We give a linear (O(|V|+|E|)) algorithm to solve this problem on a permutation graph.

Efficient algorithms for minimal disjoint path problems on chordal graphs

C.P. Gopalakrishnan, C.R. Satyan, C. Pandu Rangan (1995)

Discussiones Mathematicae Graph Theory

Disjoint paths have applications in establishing bottleneck-free communication between processors in a network. The problem of finding minimum delay disjoint paths in a network directly reduces to the problem of finding the minimal disjoint paths in the graph which models the network. Previous results for this problem on chordal graphs were an O(|V| |E|²) algorithm for 2 edge disjoint paths and an O(|V| |E|) algorithm for 2 vertex disjoint paths. In this paper, we give an O(|V| |E|) algorithm for...

Equivalence of compositional expressions and independence relations in compositional models

Francesco M. Malvestuto (2014)

Kybernetika

We generalize Jiroušek’s (right) composition operator in such a way that it can be applied to distribution functions with values in a “semifield“, and introduce (parenthesized) compositional expressions, which in some sense generalize Jiroušek’s “generating sequences” of compositional models. We say that two compositional expressions are equivalent if their evaluations always produce the same results whenever they are defined. Our first result is that a set system is star-like with centre X if...

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