Some remarks about digraphs with nonisomorphic - or -neighbourhoods
Some remarks on chromatic graphs
Some remarks on domatic numbers of graphs
Some remarks on Eulerian graphs
Some remarks on integral graphs with maximum degree four.
Some remarks on Jaeger's dual-hamiltonian conjecture
François Jaeger conjectured in 1974 that every cyclically 4-connected cubic graph is dual hamiltonian, that is to say the vertices of can be partitioned into two subsets such that each subset induces a tree in . We shall make several remarks on this conjecture.
Some remarks on Menger's theorem
Some remarks on Ramsey matroids
Some remarks on the complement of a line graph
Some remarks on the enumeration of rooted trees
Some remarks on the solutions of the equality per. (Einige Bemerkungen über die Lösungen der Gleichung per.)
Some Remarks On The Structure Of Strong K-Transitive Digraphs
A digraph D is k-transitive if the existence of a directed path (v0, v1, . . . , vk), of length k implies that (v0, vk) ∈ A(D). Clearly, a 2-transitive digraph is a transitive digraph in the usual sense. Transitive digraphs have been characterized as compositions of complete digraphs on an acyclic transitive digraph. Also, strong 3 and 4-transitive digraphs have been characterized. In this work we analyze the structure of strong k-transitive digraphs having a cycle of length at least k. We show...
Some remarks on α-domination
Let α ∈ (0,1) and let ) be a graph. According to Dunbar, Hoffman, Laskar and Markus [3] a set is called an α-dominating set of G, if for all . We prove a series of upper bounds on the α-domination number of a graph G defined as the minimum cardinality of an α-dominating set of G.
Some results concerning reconstruction conjecture
Some results concerning the ends of minimal cuts of simple graphs
Let S be a cut of a simple connected graph G. If S has no proper subset that is a cut, we say S is a minimal cut of G. To a minimal cut S, a connected component of G-S is called a fragment. And a fragment with no proper subset that is a fragment is called an end. In the paper ends are characterized and it is proved that to a connected graph G = (V,E), the number of its ends Σ ≤ |V(G)|.
Some Results on 4-Transitive Digraphs
Let D be a digraph with set of vertices V and set of arcs A. We say that D is k-transitive if for every pair of vertices u, v ∈ V, the existence of a uv-path of length k in D implies that (u, v) ∈ A. A 2-transitive digraph is a transitive digraph in the usual sense. A subset N of V is k-independent if for every pair of vertices u, v ∈ N, we have d(u, v), d(v, u) ≥ k; it is l-absorbent if for every u ∈ V N there exists v ∈ N such that d(u, v) ≤ l. A k-kernel of D is a k-independent and (k − 1)-absorbent...
Some results on chromatic polynomials of hypergraphs.
Some results on graphs with at most two positive eigenvalues.
Some results on metric trees
Using isometric embedding of metric trees into Banach spaces, this paper will investigate barycenters, type and cotype, and various measures of compactness of metric trees. A metric tree (T, d) is a metric space such that between any two of its points there is a unique arc that is isometric to an interval in ℝ. We begin our investigation by examining isometric embeddings of metric trees into Banach spaces. We then investigate the possible images x₀ = π((x₁ + ... + xₙ)/n), where π is a contractive...
Some results on semi-total signed graphs
A signed graph (or sigraph in short) is an ordered pair , where is a graph G = (V,E), called the underlying graph of S and σ:E → +, - is a function from the edge set E of into the set +,-, called the signature of S. The ×-line sigraph of S denoted by is a sigraph defined on the line graph of the graph by assigning to each edge ef of , the product of signs of the adjacent edges e and f in S. In this paper, first we define semi-total line sigraph and semi-total point sigraph of a given...