HARRY HOCHSTADT The purpose of this note is to state and prove the following theorem. Theorem. Consider the Hill's equation (1) y" +[a + q(t)]y = 0, where q(t+ir) =q(t), and q(t) is bounded. Let X,… Expand

Let K denote a compact selfadjoint operator acting on a Hilbert space H. L denotes a one dimensional selfadjoint operator also acting on H. It is shown that the eigenvalues of K and K+L interlace on… Expand