Borel incomparability of isomorphism and quasi-isomorphism for p-local groups

Let m,n3m,n\geq3 and let p,qp,q be primes. Write \oisom,p\oiso_{m,p} for isomorphism equivalence on the space of pp-local torsion-free abelian groups of rank mm, and \oqison,q\oqiso_{n,q} for quasi-isomorphism on the space of qq-local torsion-free abelian groups of rank nn. For equivalence relations EE and FF, write EBFE\perp_B F when they are Borel incomparable. Isomorphism/quasi-isomorphism incomparability conjecture.

\oisom,pB\oqison,q.\oiso_{m,p}\perp_B\oqiso_{n,q}.

This asks whether the isomorphism/quasi-isomorphism distinction is sufficient to yield Borel incomparability even when the ranks, and hence the dimensions of the acting groups, differ. The surrounding results establish incomparability for isomorphism versus isomorphism and quasi-isomorphism versus quasi-isomorphism with distinct locality primes, while the mixed case remains open.

Sources & referencesView supporting material

Primary source

Samuel Coskey, “Borel reductions of profinite actions of SL(n,Z)”, arXiv:0909.0666 (2010).

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