Global bifurcation of positive solutions of a second-order periodic boundary value problem with indefinite weight

In this paper, we are concerned with the global structure and stability of positive solutions of periodic boundary value problem -u ''(t) + q(t)u(t) = lambda a(t)f(u(t)), 0 < t < 2 pi, u(0) = u(2 pi), u'(0) = u'(2 pi), where q is an element of C(R, [0, infinity)) is of periodic 2 pi and q(t) not equivalent to 0, t is an element of [0, 2 pi]; a is an element of C(R, R) is of periodic 2 pi and changes sign. The proof of our main results are based on bifurcation techniques. (C) 2011 Elsevier Ltd. All rights reserved.