“…Soon after this, the theory of quantum symmetries was extended to finite metric spaces and finite graphs by Banica, Bichon and their collaborators (see [3,4,13], and more recently [41] and [23]), who uncovered several interesting connections to combinatorics, representation theory and free probability ( [37], [43], [5] and the references therein). The next breakthrough came through the work of Goswami and his coauthors ( [9,20]), who introduced the concept of quantum isometry groups associated to a given spectral triple á la Connes, viewed as a noncommutative differential manifold (for a general description of Goswami's theory we refer to a recent book [21], another introduction to the subject of quantum symmetry groups may be found in the lecture notes [1]). Among examples fitting in the Goswami's framework were the spectral triples associated with the group C * -algebras of discrete groups, whose quantum isometry groups were first studied in [12], and later analyzed for example in [6], [7] and [31].…”