The cyclic category makes an appearance in the studyHochschild homology gives invariants of planar algebras (see arXiv:0912.1320unital). In particular $k$-algebras for $k$ a unital, every planarcommutative ring. If we let our algebra is$A$ be the group ring $k[G]$ for $G$ a finite group, we get group homology. There are plenty of other connections to homological algebra. If we use cyclic module in two wayshomology, there are connections to geometry and topology involving the Chern character. To motivate some work on planar structure for infinite index subfactors
Von Neumann algebras are complex algebras, so we can take their Hochschild and cyclic homologies. When I want to know if there is a $II_1$have asked experts in the fields of von Neumann algebras and non-factor with nontrivialcommutative geometry about what you get, I usually hear some approximation of the following: "There's also analysis in von Neumann algebras, so I wouldn't expect an algebraic invariant like Hochschild or cyclic homology to tell you anything useful."
Although this answer makes some sense, I understand thatfind it very displeasing and cryptic. Why shouldn't it tell you something? Is there are other types of homology theories thatsome way to make more sense for"it doesn't tell you anything" quantitative? Is there an example of a von Neumann algebras, but the algebraic theory is the onealgebra with nontrivial Hochschild or cyclic homology (different from that surfaces in my work.of the complex numbers)?
NOTEEDIT: After reading the responses so far, I have edited this postshould specify that I really want to make itknow if there is a focused question$II_1$-factor with a specific goal, and it no longer resembles the original postnontrivial Hochschild or cyclic (co)homology.