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arXiv · 1402.4736

Finite Products Sets and Minimally Almost Periodic Groups

Vitaly Bergelson·Cory Christopherson·Donald Robertson·Pavel Zorin-Kranich
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Abstract

We construct, in locally compact, second countable, amenable groups, sets with large density that fail to have certain combinatorial properties. For the property of being a shift of a set of measurable recurrence we show that this is possible when the group does not have cocompact von Neumann kernel. For the stronger property of being piecewise-syndetic we show that this is always possible. For minimally almost periodic, locally compact, second countable, amenable groups, we prove that any dilation of a positive density set by an open neighborhood of the identity contains a set of measurable recurrence, and that the same result holds, up to a shift, when the von Neumann kernel is cocompact. This leads to a trichotomy for locally compact, second countable, amenable groups based on combinatorial properties of large sets. We also prove, using a two-sided Furstenberg correspondence principle, that any two-sided dilation of a positive density set contains a two-sided finite products set.

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Vitaly Bergelson, Cory Christopherson, Donald Robertson, Pavel Zorin-Kranich. 2014-02-19. Finite Products Sets and Minimally Almost Periodic Groups. https://doi.org/10.1016/j.jfa.2015.12.008

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