September 4, 2015

Uncountably many II_1 factors with non-isomorphic ultrapowers [After Boutonnet-Chifan-Ioana]

McDuff proved the existence of uncountably many non-isomorphic separable II_1 factors in 1969. In a recent paper, Boutonnet-Chifan-Ioana have shown the same family has non-isomorphic ultrapowers, thus showing the existence of a continuum of non-elementarily equivalent II_1 factors. In this seminar talk I shall present their proof.