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Torsion-free abelian groups are faithfully Borel complete and pure embeddability is a complete analytic quasi-order (2312.04162v2)
Published 7 Dec 2023 in math.LO
Abstract: In [9] we proved that the space of countable torsion-free abelian groups is Borel complete. In this paper we show that our construction from [9] satisfies several additional properties of interest. We deduce from this that countable torsion-free abelian groups are faithfully Borel complete, in fact, more strongly, we can $\mathfrak{L}_{\omega_1, \omega}$-interpret countable graphs in them. Secondly, we show that the relation of pure embeddability (equiv., elementary embeddability) among countable models of $\mathrm{Th}(\mathbb{Z}{(\omega)})$ is a complete analytic quasi-order.
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