Spectral radius and Hamiltonicity of graphs with large minimum degree

Let G be a graph of order n and lambda(G) the spectral radius of its adjacency matrix. We extend some recent results on sufficient conditions for Hamiltonian paths and cycles in G. One of the main results of the paper is the following theorem Let k aeyen 2, n aeyen k (3) + k + 4, and let G be a graph of order n, with minimum degree delta(G) aeyen k. If lambda(G) >= n - k - 1, then G has a Hamiltonian cycle, unless G = K V-1(K (n-k-1)+K (k) ) or G = K (k) V(K (n-2k) +(K) over bar (K) ).