Some existence theorems on all fractional $(g,f)$-factors with prescribed properties

Abstract

Let $G$ be a graph, and $g,f:V(G)\rightarrow Z^{+}$ with $g(x)\leq f(x)$ for each $x\in V(G)$. We say that $G$ admits all fractional $(g,f)$-factors if $G$ contains a fractional $r$-factor for every $r:V(G)\rightarrow Z^{+}$ with $g(x)\leq r(x)\leq f(x)$ for any $x\in V(G)$. Let $H$ be a subgraph of $G$. We say that $G$ has all fractional $(g,f)$-factors excluding $H$ if for every $r:V(G)\rightarrow Z^{+}$ with $g(x)\leq r(x)\leq f(x)$ for all $x\in V(G)$, $G$ has a fractional $r$-factor $F_h$ such that $E(H)\cap E(F_h)=\emptyset$, where $h:E(G)\rightarrow [0,1]$ is a function. In this paper, we show a characterization for the existence of all fractional $(g,f)$-factors excluding $H$ and obtain two sufficient conditions for a graph to have all fractional $(g,f)$-factors excluding $H$.