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| | [No title] (Site not responding. Last check: 2007-10-31) |
 | | First positive answers were given by Arnold (assuming f analytic), and by Moser (assuming f is smooth), showing that if a cannot be approximated too well by rationals, and if f is an analytic (resp., smooth) perturbation of R_a, then h is analytic (resp., smooth). |
 | | The first results that did not assume f to be a perturbation of R_a were obtained for various Diophantine conditions on a, and correspondin finite differentiability classes for f, by Herman and by Yoccoz, reducing the general case to that of a pertubration and applying an improved "implicit function theorem". |
 | | In the talks I plan to explain the role of the Diophantine properties of the rotation number, describe the phenomena, the results, and the methods developed. |
| www.math.technion.ac.il /~techm/20060613000020060615kat (282 words) |
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