Conjugation-invariant norms on the commutator subgroup of the infinite   braid group
  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. 
Mitsuaki Kimura
math.GT math.GR