Badly Approximable Numbers and the Growth Rate of the Inclusion Length of an Almost Periodic Function

Mikhail Anikushin

Published 2017-10-09Version 1

We study the growth rate of the inclusion length of an almost periodic function. For a given a. p. function such growth rate depends on the algebraic structure of Fourier exponents, i. e. on how good they can be approximated by rational numbers. In additional, as appears from the definition, the inclusion length carries some information about the translation numbers (almost periods). Our result is a lower bound of the growth rate of the inclusion interval of a quasiperiodic function (theorem 3). Here we use methods from dimension theory. We do not assume anything about exponents, but rationally independence. This suggest an idea that this lower bound can be reached (in asymptotic sense) for some "bad" exponents. Koichiro Naito in his papers on estimates of the fractal dimension of almost periodic attractors proved an upper bound of the inclusion length for some class of a.p. functions, using simultaneous Diophantine approximations. For the special case of badly approximable exponents we can see that the both estimates (if we consider them as asymptotic estimates) are coincide (see theorem 4). We hope that ideas and results presented in this paper can be useful not only to understand the nature of badly approximable numbers and almost periods, but also for more detailed understanding of the structure of almost periodic attractors.