Disconjugacy and C-disfocality of second-order self-adjoint difference equation

摘要

The disconjugacy and the C-disfocality of the second-order self-adjoint difference equationLu(t) = Delta[p(t)Delta u(t - 1)] + q(t)u(t) = 0,are discussed in this paper, where p(t) is nonzero with same sign on N(a + 1, b + 2) and q(t) is real valued on N(a + 1, b + 1). Some sufficient conditions are obtained explicitly in terms of coefficients, which can be easily verified. These results generalize some known ones in the literature. (c) 2005 Elsevier Ltd. All rights reserved.