The no infinite cocycle crossed-product decomposition conjecture for II factors
The no infinite cocycle crossed-product decomposition conjecture for II factors
Let be a separable II factor. Let be a countably infinite group, let be a tracial von Neumann algebra, and let be a trace-preserving cocycle action of on . No infinite cocycle crossed-product decomposition conjecture. There exists a separable II factor such that
for every countably infinite group , every tracial von Neumann algebra , and every trace-preserving cocycle action of on .
This would strengthen the known obstruction to scalar or finite-dimensional cocycle crossed-product decompositions. The source states that its methods do not exclude infinite-dimensional -cocycles, and more broadly that it remains open whether any II factor admits no such decomposition with an infinite group.
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Sources & referencesView supporting material
Primary source
Adriana Fernández Quero, Adrian Ioana and Hui Tan, “A class of II_1 factors without non-trivial crossed product decompositions”, arXiv:2606.31929 (2026).
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