Abstract
We introduce a new iterative amalgamated free product construction of II\(_1\) factors, and use it to construct a separable II\(_1\) factor which does not have property Gamma and is not elementarily equivalent to the free group factor \(\text {L}(\mathbb F_n)\), for any \(2\le n\le \infty \). This provides the first explicit example of two non-elementarily equivalent II\(_1\) factors without property Gamma. Moreover, our construction also provides the first explicit example of a II\(_1\) factor without property Gamma that is also not elementarily equivalent to any ultraproduct of matrix algebras. Our proofs use a blend of techniques from Voiculescu’s free entropy theory and Popa’s deformation/rigidity theory.
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Acknowledgements
We thank Isaac Goldbring, David Jekel, Jesse Peterson, Sorin Popa and Stefaan Vaes for helpful comments.
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I.C. was partially supported by NSF FRG Grant DMS-1854194 and NSF Grant DMS-2154637; A.I. was partially supported by NSF FRG Grant #1854074, NSF Grant #DMS-2153805 and a Simons Fellowship; S.K.E was supported by a Simons Postdoctoral Fellowship.
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Chifan, I., Ioana, A. & Kunnawalkam Elayavalli, S. An exotic II\(_1\) factor without property Gamma. Geom. Funct. Anal. 33, 1243–1265 (2023). https://doi.org/10.1007/s00039-023-00649-4
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DOI: https://doi.org/10.1007/s00039-023-00649-4