On a class of operators in the hyperfinite $\mathrm{II}_1$ factor


  • Zhangsheng Zhu
  • Junsheng Fang
  • Rui Shi




Let $R$ be the hyperfinite $\mathrm {II}_1$ factor and let $u$, $v$ be two generators of $R$ such that $u^*u=v^*v=1$ and $vu=e^{2\pi i\theta } uv$ for an irrational number $\theta$. In this paper we study the class of operators $uf(v)$, where $f$ is a bounded Lebesgue measurable function on the unit circle $S^1$. We calculate the spectrum and Brown spectrum of operators $uf(v)$, and study the invariant subspace problem of such operators relative to $R$. We show that under general assumptions the von Neumann algebra generated by $uf(v)$ is an irreducible subfactor of $R$ with index $n$ for some natural number $n$, and the $C^*$-algebra generated by $uf(v)$ and the identity operator is a generalized universal irrational rotation $C^*$-algebra.


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How to Cite

Zhu, Z., Fang, J., & Shi, R. (2017). On a class of operators in the hyperfinite $\mathrm{II}_1$ factor. MATHEMATICA SCANDINAVICA, 120(2), 249–271. https://doi.org/10.7146/math.scand.a-25625