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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...

Contractible edges in some k -connected graphs

Yingqiu Yang, Liang Sun (2012)

Czechoslovak Mathematical Journal

An edge e of a k -connected graph G is said to be k -contractible (or simply contractible) if the graph obtained from G by contracting e (i.e., deleting e and identifying its ends, finally, replacing each of the resulting pairs of double edges by a single edge) is still k -connected. In 2002, Kawarabayashi proved that for any odd integer k 5 , if G is a k -connected graph and G contains no subgraph D = K 1 + ( K 2 K 1 , 2 ) , then G has a k -contractible edge. In this paper, by generalizing this result, we prove that for any integer...

Control flow graphs and code coverage

Robert Gold (2010)

International Journal of Applied Mathematics and Computer Science

The control flow of programs can be represented by directed graphs. In this paper we provide a uniform and detailed formal basis for control flow graphs combining known definitions and results with new aspects. Two graph reductions are defined using only syntactical information about the graphs, but no semantical information about the represented programs. We prove some properties of reduced graphs and also about the paths in reduced graphs. Based on graphs, we define statement coverage and branch...

Controllable graphs

D. Cvetković, P. Rowlinson, Z. Stanić, M. G. Yoon (2011)

Bulletin, Classe des Sciences Mathématiques et Naturelles, Sciences mathématiques

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