We study projective dimension, a graph parameter (denoted by pd(G) for a graph G), introduced by Pudlák and Rödl [13], who showed that proving lower bounds for pd(Gf ) for bipartite graphs Gf associated with a Boolean function f imply size lower bounds for branching programs computing f . Despite several attempts [13, 17], proving super-linear lower bounds for projective dimension of explicit f...

Given a graph L, in this article we investigate the anti-Ramsey number χS (n,e,L), defined to be the minimum number of colors needed to edge-color some graph G(n,e) with n vertices and e edges so that in every copy of L inG all edges have different colors. We call such a copy of L totally multicolored (TMC). In [7] among many other interesting results and problems, Burr, Erdős, Graham, and T. S...

When the degree of saturation at intersection approaches one, Webster’s optimum cycle length equation becomes inapplicable, because the cycle length will becomes very big when the degree of saturation approaches one and will be fully unrealistic when the degree of saturation becomes greater than one. This is not a problem for HCM2000 method. But optimum cycle length calculation in this method h...

Two characterizations of hypercubes are given: 1) A graph is a hypercube if and only if it is antipodal and bipartite (0, 2)-graph. 2) A graph is an nhypercube if and only if there are n pairs of prime convexes, the graph is a prime convex intersection graph, and each intersection of n prime convexes (no one of which is from the same pair) is a vertex.

This paper focuses on the relationship between an $L$-subset and the system of level-elements induced by it, where the underlying lattice $L$ is a complete residuated lattice and the domain set of $L$-subset is an $L$-partially ordered set $(X,P)$. Firstly, we obtain the sufficient and necessary condition that an $L$-subset is represented by its system of level-elements. Then, a new representat...

Extending the work of K. L. Collins and A.N. Trenk, we characterize connected bipartite graphs with large distinguishing chromatic number. In particular, if G is a connected bipartite graph with maximum degree ∆ ≥ 3, then χD(G) ≤ 2∆ − 2 whenever G 6∼= K∆−1,∆, K∆,∆.

The biclique cover number (resp. biclique partition number) of a graph G, bc(G) (resp. bp(G)), is the least number of bicliques—complete bipartite subgraphs—that are needed to cover (resp. partition) the edges of G. The local biclique cover number (resp. local biclique partition number) of a graph G, lbc(G) (resp. lbp(G)), is the least r such that there is a cover (resp. partition) of the edges...

The families EPT (resp. EPG) Edge Intersection Graphs of Paths in a tree (resp. in a grid) are well studied graph classes. Recently we introduced the graph classes Edge-Intersecting and Non-Splitting Paths in a Tree (ENPT), and in a Grid (ENPG). It was shown that ENPG contains an infinite hierarchy of subclasses that are obtained by restricting the number of bends in the paths. Motivated by thi...

Received Let G = (V; E) be a graph with n vertices, chromatic number (G) and list chromatic number`(G): Suppose each vertex of V (G) is assigned a list of t colors. Albertson, Grossman and Haas 1] conjectured that at least t ` (G) n vertices can be colored properly from these lists. Albertson et. al. 1] and Chappell 3] proved partial results concerning this conjecture. This paper presents algor...