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On the Circumference of 2-Connected $$mathcal{P}_{3}$$-Dominated Graphs
Authors:Jiangyan Guo  Elkin Vumar
Affiliation:(1) College of Mathematic and System Sciences, Xinjiang University, Urumqi, 830046, P.R. China
Abstract:Let G be a connected graph. For $$x, y in V(G)$$ at distance 2, we define $$J(x, y) = {u|u in N(x) cap N(y), N[u] subseteq N[x] cup N[y]}$$, and $$J^{prime}(x, y) = {u|u in N (x) cap N(y)$$, if $$v in N(u) setminus (N [x] cup N[y])$$ then $$(N(u) cup N(x) cup N(y)) setminus {x,y,v} subseteq N(v)}$$. G is quasi-claw-free$$({mathcal{QCF}})$$ if it satisfies $$J(x, y) neq emptyset$$, and G is P 3-dominated($$mathcal{P}_{3}{mathcal{D}}$$) if it satisfies $$J(x,y)cup J^{prime} (x,y) neq emptyset$$, for every pair (x, y) of vertices at distance 2. Certainly $${mathcal{P}}_3 {mathcal{D}}$$ contains $${mathcal{QCF}}$$ as a subclass. In this paper, we prove that the circumference of a 2-connected P 3-dominated graph G on n vertices is at least min $${3delta+2,n}$$ or $$G in {mathcal{F}} cup {K_{2,3}, K_{1,1,3}}$$, moreover if $$n leq 4delta$$ then G is hamiltonian or $$G in {mathcal{F}}cup{K_{2,3}, K_{1,1,3}}$$, where $${mathcal{F}}$$ is a class of 2-connected nonhamiltonian graphs.
Keywords:Circumference  Quasi-claw-free graph   P 3-Dominated graph  Hamiltonian graph
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