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Generalized Polynomials and Mild Mixing
Published online by Cambridge University Press: 20 November 2018
Abstract
An unsettled conjecture of V. Bergelson and I. Håland proposes that if $(X,\,\mathcal{A},\,\mu ,\,T)$ is an invertible weak mixing measure preserving system, where
$\mu (X)<\infty $, and if
${{p}_{1}},{{p}_{2}},...,{{p}_{k}}$ are generalized polynomials (functions built out of regular polynomials via iterated use of the greatest integer or floor function) having the property that no
${{p}_{i}}$, nor any
${{p}_{i}}-{{p}_{j,}}i\ne j$, is constant on a set of positive density, then for any measurable sets
${{A}_{0}},{{A}_{1}},...,{{A}_{K}}$, there exists a zero-density set
$E\subset Z$ such that
1$$\underset{n\notin E}{\mathop{\underset{n\to \infty }{\mathop{\lim }}\,}}\,\mu ({{A}_{0}}\cap {{T}^{p1(n)}}{{A}_{1}}\cap \ldots \cap {{T}^{pk(n)}}{{A}_{k}})=\prod\limits_{i=0}^{k}{\mu ({{A}_{i}}).}$$
We formulate and prove a faithful version of this conjecture for mildly mixing systems and partially characterize, in the degree two case, the set of families $\left\{ {{p}_{1}},{{p}_{2}},\,.\,.\,.\,,\,{{p}_{k}} \right\}$ satisfying the hypotheses of this theorem.
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- Research Article
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- Copyright © Canadian Mathematical Society 2009
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