Conjugation-invariant norms on the commutator subgroup of the infinite braid group

Abstract: In this paper, we give a proof of the result of Brandenbursky and K\c{e}dra which says that the commutator subgroup of the infinite braid group admits stably unbounded norms. Moreover, we observe the norms which we constructed are equivalent to the biinvariant word norm studied by Brandenbursky and K\c{e}dra.