The notion of a pinned equivalence relation is useful in proofs of irreducibility between Borel equivalence relations. Kechris conjectured that the smallest unpinned equivalence relation is equality of countable sets of reals. I will show that the answer is negative using old ideas of Shelah regarding Borel sets in the plane containing large squares. The talk will include the necessary background.
Solution to the pinned conjecture
09.12.2010 15:00 - 16:30
Organiser:
KGRC
Location:
SR 101, 2. St., Währinger Str. 25