Factors with Multiple Degree Constraints in Graphs

نویسندگان

  • Richard C. Brewster
  • Sean McGuinness
  • Morten Hegner Nielsen
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.

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عنوان ژورنال:
  • SIAM J. Discrete Math.

دوره 27  شماره 

صفحات  -

تاریخ انتشار 2013