Connes-Landi spheres are homogeneous spaces

In this paper, we review some recent developments of compact quantum groups that arise as $\theta$-deformations of compact Lie groups of rank at least two. A $\theta$-deformation is merely a 2-cocycle deformation using an action of a torus of dimension higher than 2. Using the formula (Lemma 5.3) developed in \cite{W2018}, we derive the noncommutative 7-sphere in the sense of Connes and Landi \cite{CL2001} as the fixed-point subalgebra.