Michael C. Laskowski, Danielle S. Ulrich
Published 2022-09-14Version 1
We prove that for a countable, commutative ring $R$, the class of countable $R$-modules either has only countably many isomorphism types, or else it is Borel complete. The machinery gives a succinct proof of the Borel completeness of TFAB, the class of torsion-free abelian groups. We also prove that for any countable ring $R$, both the class of left $R$-modules endowed with an endomorphism and the class of left $R$-modules with four named submodules are Borel complete.
Torsion-Free Abelian Groups are Borel Complete
The quandary of quandles: The Borel completeness of a knot invariant
Torsion-free abelian groups of finite rank and fields of finite transcendence degree
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