The precise regularity of the Lyapunov exponent for $C^2$ Cos-type quasiperiodic Schr\"odinger cocycles with large couplings

Abstract

In this paper, we study the regularity of the Lyapunov exponent for quasiperiodic Schr\"odinger cocycles with $C^2$ cos-type potentials, large coupling constants, and a fixed Diophantine frequency. We obtain the absolute continuity of the Lyapunov exponent. Moreover, we prove the Lyapunov exponent is $\frac{1}{2}$-H\"older continuous. Furthermore, for any given $r\in (\frac12, 1)$, we can find some energy in the spectrum where the local regularity of the Lyapunov exponent is between $(r-\epsilon)$-H\"older continuity and $(r+\epsilon)$-H\"older continuity.