2010 seminar talk: On the complexity of the relations of isomorphism and bi-embeddability

Talk held by Luca Motto Ros (KGRC) at the KGRC seminar on 2010-01-28.


Given a pair of analytic equivalence relations E and F, we determine under which conditions it is possible to find an Lω1-elementary class C such that E and F are Borel equivalent to, respectively, isomorphism and bi- embeddability on C: quite surprisingly, it turns out that, apart from the obvious limitations, such an elementary class always exists. This result gives an (almost complete) answer to previous questions of Louveau-Rosendal (2005) and Friedman-Motto Ros (2009).

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Kurt Gödel Research Center for Mathematical Logic. Währinger Straße 25, 1090 Wien, Austria. Phone +43-1-4277-50501. Last updated: 2010-12-16, 04:37.