Displaying 521 – 540 of 1226

Showing per page

A note on the number of squares in a partial word with one hole

Francine Blanchet-Sadri, Robert Mercaş (2009)

RAIRO - Theoretical Informatics and Applications

A well known result of Fraenkel and Simpson states that the number of distinct squares in a word of length n is bounded by 2n since at each position there are at most two distinct squares whose last occurrence starts. In this paper, we investigate squares in partial words with one hole, or sequences over a finite alphabet that have a “do not know” symbol or “hole”. A square in a partial word over a given alphabet has the form uv where u is compatible with v, and consequently, such square is...

A note on the open packing number in graphs

Mehdi Mohammadi, Mohammad Maghasedi (2019)

Mathematica Bohemica

A subset S of vertices in a graph G is an open packing set if no pair of vertices of S has a common neighbor in G . An open packing set which is not a proper subset of any open packing set is called a maximal open packing set. The maximum cardinality of an open packing set is called the open packing number and is denoted by ρ o ( G ) . A subset S in a graph G with no isolated vertex is called a total dominating set if any vertex of G is adjacent to some vertex of S . The total domination number of G , denoted...

A Note on the Permanental Roots of Bipartite Graphs

Heping Zhang, Shunyi Liu, Wei Li (2014)

Discussiones Mathematicae Graph Theory

It is well-known that any graph has all real eigenvalues and a graph is bipartite if and only if its spectrum is symmetric with respect to the origin. We are interested in finding whether the permanental roots of a bipartite graph G have symmetric property as the spectrum of G. In this note, we show that the permanental roots of bipartite graphs are symmetric with respect to the real and imaginary axes. Furthermore, we prove that any graph has no negative real permanental root, and any graph containing...

Currently displaying 521 – 540 of 1226