Narrow Results

For a set ${𝒦}$ of connected graphs, a spanning subgraph $H$ of $G$ is called a ${𝒦}$-factor if each component of $H$ is isomorphic to a member of ${𝒦}$. In this paper, some sufficient conditions with regard to tight toughness, isolated toughness and binding number bounds to guarantee the existence of the $\{K_{1,j}:1\le j\le 2k\}$-factor and $\{P_2,P_5\}$-factor for any graph are obtained.

The $\{K_{1,1},K_{1,2},\dots ,K_{1,k},{𝒯}(2k+1)\}$-factor and $\{K_{1,2},K_{1,3},K_5\}$-factor of a graph are a spanning subgraph whose each component is an element of $\{K_{1,1},K_{1,2},\dots ,K_{1,k},{𝒯}(2k+1)\}$ and $\{K_{1,2},K_{1,3},K_5\}$, respectively, where ${𝒯}(2k+1)$ is a special family of trees. In this paper, we obtain a sufficient condition in terms of tight toughness, isolated toughness and binding number bounds to guarantee the existence of a $\{K_{1,1},K_{1,2},\dots ,K_{1,k},{𝒯}(2k+1)\}$-factor and $\{K_{1,2},K_{1,3},K_5\}$-factor for any graph.

For a set ${\mathscr{H}}$ of connected graphs, a spanning subgraph $H$ of a graph $G$ is an ${\mathscr{H}}$-factor if every component of $H$ is isomorphic to some member of ${\mathscr{H}}$. In this paper, we give a criterion for the existence of tight toughness, isolated toughness and binding number bounds in a graph of a strong ${𝒮}$-star factor, $\{1,3,\dots ,2n-1\}$-factor and $f$-star factor. Moreover, we show that the bounds of the sufficient conditions are sharp.