Factors with Multiple Degree Constraints in Graphs
نویسندگان
چکیده
For a graph G and for each vertex v ∈ V (G), let ΛG(v) = {EG(v, 1), EG(v, 2), . . . , EG(v, kv)} be a partition of the edges incident with v. Let ΛG = {ΛG(v) ∣∣ v ∈ V (G)}. We call the pair (G,ΛG) a partitioned graph. Let k = maxv kv and let g, f : V (G)×{1, . . . , k} → N and t, u : V (G)→ N be functions where for all vertices v ∈ V (G) (i) g(v, i) ≤ f(v, i) ≤ dG(v, i) i = 1, . . . , kv (ii) u(v) ≤ t(v) ≤ dG(v) (iii) u(v) ≤ ∑kv i=1 f(v, i) and ∑kv i=1 g(v, i) ≤ t(v). A subgraph H of the partitioned graph is said to be a (g, f, u, t)factor if all vertices v ∈ V (G) satisfy (a) g(v, i) ≤ dH(v, i) ≤ f(v, i), i = 1, . . . , kv and (b) u(v) ≤ dH(v) ≤ t(v) where dH(v, i) = |E(H) ∩ EG(v, i)|. In this paper, we shall show via a reduction to a matching problem, that there is a good algorithm for determining whether a partitioned graph has a (g, f, u, t)-factor. Secondly, we shall also prove a theorem which characterizes the existence of (0, f, t, u)-factors in a partitioned graph when u(v) < f(v, i) for all v and i. As a special case, we obtain Lovász’s (g, f)-factor theorem.
منابع مشابه
Splice Graphs and their Vertex-Degree-Based Invariants
Let G_1 and G_2 be simple connected graphs with disjoint vertex sets V(G_1) and V(G_2), respectively. For given vertices a_1in V(G_1) and a_2in V(G_2), a splice of G_1 and G_2 by vertices a_1 and a_2 is defined by identifying the vertices a_1 and a_2 in the union of G_1 and G_2. In this paper, we present exact formulas for computing some vertex-degree-based graph invariants of splice of graphs.
متن کاملBalanced Degree-Magic Labelings of Complete Bipartite Graphs under Binary Operations
A graph is called supermagic if there is a labeling of edges where the edges are labeled with consecutive distinct positive integers such that the sum of the labels of all edges incident with any vertex is constant. A graph G is called degree-magic if there is a labeling of the edges by integers 1, 2, ..., |E(G)| such that the sum of the labels of the edges incident with any vertex v is equal t...
متن کاملOn reverse degree distance of unicyclic graphs
The reverse degree distance of a connected graph $G$ is defined in discrete mathematical chemistry as [ r (G)=2(n-1)md-sum_{uin V(G)}d_G(u)D_G(u), ] where $n$, $m$ and $d$ are the number of vertices, the number of edges and the diameter of $G$, respectively, $d_G(u)$ is the degree of vertex $u$, $D_G(u)$ is the sum of distance between vertex $u$ and all other vertices of $G$, and $V(G)$ is the...
متن کاملGeneralized Degree Distance of Strong Product of Graphs
In this paper, the exact formulae for the generalized degree distance, degree distance and reciprocal degree distance of strong product of a connected and the complete multipartite graph with partite sets of sizes m0, m1, . . . , mr&minus1 are obtained. Using the results obtained here, the formulae for the degree distance and reciprocal degree distance of the closed and open fence graphs are co...
متن کاملNote on multiple Zagreb indices
The Zagreb indices are the oldest graph invariants used in mathematical chemistry to predict the chemical phenomena. In this paper we define the multiple versions of Zagreb indices based on degrees of vertices in a given graph and then we compute the first and second extremal graphs for them.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- SIAM J. Discrete Math.
دوره 27 شماره
صفحات -
تاریخ انتشار 2013