Livšic Regularity Theorems for Twisted Cocycle Equations Over Hyperbolic Systems

Abstract

Let Φ be a hyperbolic map. Cocycle equations of the form f = uΦ·g·αu−1 are considered, with f, g, u taking values in a compact connected Lie group G, α being an automorphism of G and f, g being Hölder continuous. When the eigenvalues of the derivative of α have modulus 1, it is proved that any measurable solution u has a Hölder continuous version. This condition on α is optimal. When f, g are Ck then u may be taken to be Ck−1+ε for any ε ∈ (0, 1).