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Effective multi-scale approach to the Schrödinger cocycle over a skew-shift base

Published online by Cambridge University Press:  17 April 2019

R. HAN
Affiliation:
School of Mathematics, Georgia Institute of Technology, Atlanta, GA30332, USA email [email protected]
M. LEMM
Affiliation:
Harvard University, Department of Mathematics, 1 Oxford Street, Cambridge, MA02138, USA email [email protected]
W. SCHLAG
Affiliation:
Yale University, Department of Mathematics, 10 Hillhouse Ave, New Haven, CT06511, USA email [email protected]

Abstract

We prove a conditional theorem on the positivity of the Lyapunov exponent for a Schrödinger cocycle over a skew-shift base with a cosine potential and the golden ratio as frequency. For coupling below 1, which is the threshold for Herman’s subharmonicity trick, we formulate three conditions on the Lyapunov exponent in a finite but large volume and on the associated large-deviation estimates at that scale. Our main results demonstrate that these finite-size conditions imply the positivity of the infinite-volume Lyapunov exponent. This paper shows that it is possible to make the techniques developed for the study of Schrödinger operators with deterministic potentials, based on large-deviation estimates and the avalanche principle, effective.

Type
Original Article
Copyright
© Cambridge University Press, 2019

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