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Singular measures for class P-circle homeomorphisms with several break points
Published online by Cambridge University Press: 30 November 2012
Abstract
Let f be a class P-homeomorphism of the circle with break point singularities, that is, differentiable except at some singular points where the derivative has a jump. Let f have irrational rotation number and Df be absolutely continuous on every continuity interval of Df. We prove that if the product of the f-jumps along any subset of break points is distinct from 1 then the invariant measure μf is singular with respect to the Haar measure. This result generalizes previous results obtained by Dzhalilov and Khanin, Dzhalilov, Akhadkulov, Dzhalilov–Liousse and Mayer. Moreover, we prove that if the rotation number ρ(f) is irrational of bounded type then (a) if the product of the f-jumps on some orbit is distinct from 1 then the invariant measure μf is singular with respect to the Haar measure m, and (b) if the product of the f-jumps on each orbit is equal to 1 and D2f∈Lp (S1) for some p>1 then μfis equivalent to the Haar measure.
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- ©2012 Cambridge University Press
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