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A structure theorem for stochastic processes indexed by the discrete hypercube

Part of: Stochastic processes Extremal combinatorics

Published online by Cambridge University Press:  28 January 2021

Pandelis Dodos  and
Konstantinos Tyros
Pandelis Dodos
Affiliation:
Department of Mathematics, University of Athens, Panepistimiopolis 157 84, Athens, Greece; E-mail: pdodos@math.uoa.gr
Konstantinos Tyros
Affiliation:
Department of Mathematics, University of Athens, Panepistimiopolis 157 84, Athens, Greece; E-mail: ktyros@math.uoa.gr

Abstract

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Let A be a finite set with , let n be a positive integer, and let $A^n$ denote the discrete $n\text {-dimensional}$ hypercube (that is, $A^n$ is the Cartesian product of n many copies of A). Given a family $\langle D_t:t\in A^n\rangle $ of measurable events in a probability space (a stochastic process), what structural information can be obtained assuming that the events $\langle D_t:t\in A^n\rangle $ are not behaving as if they were independent? We obtain an answer to this problem (in a strong quantitative sense) subject to a mild ‘stationarity’ condition. Our result has a number of combinatorial consequences, including a new (and the most informative so far) proof of the density Hales-Jewett theorem.

MSC classification

Primary: 05D10: Ramsey theory 05D40: Probabilistic methods
Secondary: 60G99: None of the above, but in this section
Type
Foundations
Information
Forum of Mathematics, Sigma , Volume 9 , 2021 , e8
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Creative Commons
Creative Common License - CCCreative Common License - BY
This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright
© The Author(s), 2021. Published by Cambridge University Press

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