Fine Structure of the Zeros of Orthogonal Polynomials, IV. A Priori   Bounds and Clock Behavior
  We prove locally uniform spacing for the zeros of orthogonal polynomials on the real line under weak conditions (Jacobi parameters approach the free ones and are of bounded variation). We prove that for ergodic discrete Schrodinger operators, Poisson behavior implies positive Lyapunov exponent. Both results depend on a priori bounds on eigenvalue spacings for which we provide several proofs. 
Yoram Last and Barry Simon