Continuity of the Lyapunov Exponent for analytic quasi-perodic cocycles   with singularities
  We prove that the Lyapunov exponent of quasi-periodic cocyles with singularities behaves continuously over the analytic category. We thereby generalize earlier results, where singularities were either excluded completely or constrained by additional hypotheses. Applications are one-parameter families of analytic Jacobi operators, such as extended Harper's model describing crystals subject to external magnetic fields. 
S. Jitomirskaya and C. A. Marx
math.DS math-ph math.MP