English

Stability of rotation relations in $C^*$-algebras

Operator Algebras 2020-05-20 v2

Abstract

Let Θ=(θj,k)3×3\Theta=(\theta_{j,k})_{3\times 3} be a non-degenerate real skew-symmetric 3×33\times 3 matrix, where θj,k[0,1).\theta_{j,k}\in [0,1). For any ε>0\varepsilon>0, we prove that there exists δ>0\delta>0 satisfying the following: if v1,v2,v3v_1,v_2,v_3 are three unitaries in any unital simple separable CC^*-algebra AA with tracial rank at most one, such that vkvje2πiθj,kvjvk<δ\mboxand12πiτ(logθ(vkvjvkvj))=θj,k\|v_kv_j-e^{2\pi i \theta_{j,k}}v_jv_k\|<\delta \,\,\,\, \mbox{and}\,\,\,\, \frac{1}{2\pi i}\tau(\log_{\theta}(v_kv_jv_k^*v_j^*))=\theta_{j,k} for all τT(A)\tau\in T(A) and j,k=1,2,3,j,k=1,2,3, where logθ\log_{\theta} is a continuous branch of logarithm for some real number θ[0,1)\theta\in [0, 1), then there exists a triple of unitaries v~1,v~2,v~3A\tilde{v}_1,\tilde{v}_2,\tilde{v}_3\in A such that v~kv~j=e2πiθj,kv~jv~k\mboxandv~jvj<ε,j,k=1,2,3.\tilde{v}_k\tilde{v}_j=e^{2\pi i\theta_{j,k} }\tilde{v}_j\tilde{v}_k\,\,\,\,\mbox{and}\,\,\,\,\|\tilde{v}_j-v_j\|<\varepsilon,\,\,j,k=1,2,3. The same conclusion holds if Θ\Theta is rational or non-degenerate and AA is a nuclear purely infinite simple CC^*-algebra (where the trace condition is vacuous). If Θ\Theta is degenerate and AA has tracial rank at most one or is nuclear purely infinite simple, we provide some additional injectivity condition to get the above conclusion.

Keywords

Cite

@article{arxiv.1808.05725,
  title  = {Stability of rotation relations in $C^*$-algebras},
  author = {Jiajie Hua and Qingyun Wang},
  journal= {arXiv preprint arXiv:1808.05725},
  year   = {2020}
}

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31 pages