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JOURNALS // Zapiski Nauchnykh Seminarov POMI // Archive

Zap. Nauchn. Sem. POMI, 2005 Volume 326, Pages 28–47 (Mi znsl336)

This article is cited in 12 papers

Erdős measures, sofic measures, and Markov chains

Z. I. Bezhaevaa, V. I. Oseledetsb

a Moscow State Institute of Electronics and Mathematics
b M. V. Lomonosov Moscow State University

Abstract: We consider random variable $\zeta=\xi_1\rho+\xi_2\rho^2+\ldots$ where $\xi_1,\xi_2,\ldots$ are independent identically distibuted random variables taking values 0, 1, with $P(\xi_i=0)=p_0$, $P(\xi_i=1)=p_1$, $0<p_0<1$. Let $\beta=1/\rho$ be the golden number.
The Fibonacci expansion for a random point $\rho\zeta$ from $[0,1]$ is of form $\eta_1\rho+\eta_2\rho^2+\ldots$ where random variables $\eta_k=0,1$ and $\eta_k\eta_{k+1}=0$. The infinite random word $\eta=\eta_1\eta_2\ldots\eta_n\ldots$ takes values in the Fibonacci compactum and defines an Erdős measure $\mu(A)=P(\eta\in A)$ on it. The invariant Erdős measure is the shift-invariant measure with respect to which Erdős measure is absolutely continuous.
We show that Erdős measures are sofic. Recall that a sofic system is a symbolic system which is a continuous factor of a topological Markov chain. A sofic measure is a one-block (or symbol to symbol) factor of the measure corresponding to a homogeneous Markov chain. For Erdős measures the corresponding regular Markov chain has 5 states. This gives ergodic properties of the invariant Erdős measure.
We give a new ergodic theory proof of the singularity of the distribution of the random variable $\zeta$. Our method is also applicable when $\xi_1,\xi_2,\ldots$ is a stationary Markov chain taking values 0, 1. In particular, we prove that the distribution of $\zeta$ is singular and that Erdős measures appear as result of gluing together states in a regular Markov chain with 7 states.

UDC: 519.217, 517.518.1

Received: 08.04.2005


 English version:
Journal of Mathematical Sciences (New York), 2007, 140:3, 357–368

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