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Limit theorems for counting large continued fraction digits

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Abstract

We establish a central limit theorem for counting large continued fraction digits (an), that is, we count occurrences {an>bn}, where (bn) is a sequence of positive integers. Our result improves a similar result by Philipp, which additionally assumes that bn tends to infinity. Moreover, we give a refinement of the famous Borel–Bernstein theorem for continued fractions regarding the event that the nth continued fraction digit lies infinitely often between dn and dn(1 + 1/cn) for given sequences (cn) and (dn). Also, for these sets, we obtain a central limit theorem. As an interesting side result, we explicitly determine the first φ-mixing coefficient for the Gauss system.

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Correspondence to Marc Kesseböhmer.

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This research was supported by the German Research Foundation (DFG) grant “Renewal Theory and Statistics of Rare Events in Infinite Ergodic Theory” (Geschäftszeichen KE 1440/2-1). The research of TS was conducted at University of Bremen and at the Australian National University. While at University of Bremen TS was supported by the Studienstiftung des Deutschen Volkes.

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Kesseböhmer, M., Schindler, T.I. Limit theorems for counting large continued fraction digits. Lith Math J 60, 189–207 (2020). https://doi.org/10.1007/s10986-020-09479-5

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