
We prove that the Borel space of torsion-free Abelian groups with domain $ω$ is Borel complete, i.e., the isomorphism relation on this Borel space is as complicated as possible, as an isomorphism relation. This solves a long-standing open problem in descriptive set theory, which dates back to the seminal paper on Borel reducibility of Friedman and Stanley from 1989.
Automorphisms, homomorphisms, endomorphisms, etc. for abelian groups, torsion-free abelian groups; Borel completeness; complexity of isomorphism, 03E15, 20K20, 20K30, Mathematics - Logic, Group Theory (math.GR), Torsion-free groups, infinite rank, torsion-free abelian groups, FOS: Mathematics, complexity of isomorphism, Borel completeness, Logic (math.LO), Descriptive set theory, Mathematics - Group Theory
Automorphisms, homomorphisms, endomorphisms, etc. for abelian groups, torsion-free abelian groups; Borel completeness; complexity of isomorphism, 03E15, 20K20, 20K30, Mathematics - Logic, Group Theory (math.GR), Torsion-free groups, infinite rank, torsion-free abelian groups, FOS: Mathematics, complexity of isomorphism, Borel completeness, Logic (math.LO), Descriptive set theory, Mathematics - Group Theory
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