All a b c d e f g h i j k l m n o p q r s t u v w x y z Other

Previous Page 58 Next

Displaying 1141 – 1160 of 5365

Showing per page

Constrained Colouring and σ-Hypergraphs

Yair Caro, Josef Lauri, Christina Zarb (2015)

Discussiones Mathematicae Graph Theory

A constrained colouring or, more specifically, an (α, β)-colouring of a hypergraph H, is an assignment of colours to its vertices such that no edge of H contains less than α or more than β vertices with different colours. This notion, introduced by Bujtás and Tuza, generalises both classical hypergraph colourings and more general Voloshin colourings of hypergraphs. In fact, for r-uniform hypergraphs, classical colourings correspond to (2, r)-colourings while an important instance of Voloshin colourings...

Constrained Steiner trees in Halin graphs

Guangting Chen, Rainer E. Burkard (2003)

RAIRO - Operations Research - Recherche Opérationnelle

In this paper, we study the problem of computing a minimum cost Steiner tree subject to a weight constraint in a Halin graph where each edge has a nonnegative integer cost and a nonnegative integer weight. We prove the NP-hardness of this problem and present a fully polynomial time approximation scheme for this NP-hard problem.

Constrained Steiner trees in Halin graphs

Guangting Chen, Rainer E. Burkard (2010)

RAIRO - Operations Research

In this paper, we study the problem of computing a minimum cost Steiner tree subject to a weight constraint in a Halin graph where each edge has a nonnegative integer cost and a nonnegative integer weight. We prove the NP-hardness of this problem and present a fully polynomial time approximation scheme for this NP-hard problem.

Constructions for type I trees with nonisomorphic Perron branches

Stephen J. Kirkland (1999)

Czechoslovak Mathematical Journal

A tree is classified as being type I provided that there are two or more Perron branches at its characteristic vertex. The question arises as to how one might construct such a tree in which the Perron branches at the characteristic vertex are not isomorphic. Motivated by an example of Grone and Merris, we produce a large class of such trees, and show how to construct others from them. We also investigate some of the properties of a subclass of these trees. Throughout, we exploit connections between...

Constructions over tournaments

Jaroslav Ježek (2003)

Czechoslovak Mathematical Journal

We investigate tournaments that are projective in the variety that they generate, and free algebras over partial tournaments in that variety. We prove that the variety determined by three-variable equations of tournaments is not locally finite. We also construct infinitely many finite, pairwise incomparable simple tournaments.

Containers and wide diameters of P 3 ( G )

Daniela Ferrero, Manju K. Menon, A. Vijayakumar (2012)

Mathematica Bohemica

The P 3 intersection graph of a graph G has for vertices all the induced paths of order 3 in G . Two vertices in P 3 ( G ) are adjacent if the corresponding paths in G are not disjoint. A w -container between two different vertices u and v in a graph G is a set of w internally vertex disjoint paths between u and v . The length of a container is the length of the longest path in it. The w -wide diameter of G is the minimum number l such that there is a w -container of length at most l between any pair of different...

Currently displaying 1141 – 1160 of 5365