Degree conditions for Hamiltonian graphs to have [a,b] -factors containing a given Hamiltonian cycle

Let 1≤a<b be integers and G a Hamiltonian graph of order |G|≥(a+b)(2a+b)/b. Suppose that δ(G)≥a+2 and max{deg _G(x),deg_G(y)}≥a|G|/(a+b)+2 for each pair of nonadjacent vertices x and y in G. Then G has an [a,b]-factor which is edge-disjoint from a given Hamiltonian cycle. The lower bound on the degree condition is sharp. For the case of odd a = b, there exists a graph satisfying the conditions of the theorem but having no desired factor. As consequences, we have the degree conditions for Hamiltonian graphs to have [a,b]-factors containing a given Hamiltonian cycle.