In this paper we use topological degree theory and critical point theory to
investigate the existence of weak solutions for the second order impulsive
boundary value problem {-x??(t)- ?x(t) = f (t), t ? tj, t ?
(0,?), ?x?(tj) = x?(t+j)- x?(t-j) = Ij(x(tj)), j=1,2,..., p,
x(0) = x(?) = 0, where ? is a positive parameter, 0 = t0 < t1 < t2 < ... <
tp < tp+1 = ?, f ? L2(0,?) is a given function and Ij ? C(R,R) for j = 1,2,..., p.