Infinite conjugacy class property

In mathematics, a group is said to have the infinite conjugacy class property, or to be an icc group, if the conjugacy class of every group element but the identity is infinite.

The von Neumann group algebra of a group is a factor if and only if the group has the infinite conjugacy class property. It will then be, provided the group is nontrivial, of type II₁, i.e. it will possess a unique, faithful, tracial state.

Examples for icc groups are the group of permutations of finitely many elements of an infinite set, and free groups on two generators.

In abelian groups, every conjugacy class consists of only one element, so icc groups are, in a way, as far from being abelian as possible.