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arXiv · 2605.17411

Combinatorics of Schur ultrafilters

S. Bardyla
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Abstract

In this paper, we provide a combinatorial characterization of the elements of Schur ultrafilters on countable commutative groups. Using this characterization, we construct a free Schur ultrafilter on $\mathbb Z$ that is not infinitary Schur. Moreover, assuming the Continuum Hypothesis, we establish the existence of a free Schur P-point on $\mathbb Z$.

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S. Bardyla. 2026-05-17. Combinatorics of Schur ultrafilters. https://arxiv.org/abs/2605.17411

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