Exponentially distorted subgroup (source code)

= Exponentially distorted subgroup

A subgroup is exponentially distorted when elements with intrinsic length exponential in $n$ can have ambient length linear in $n$. In $\operatorname{BS}(1,2)$, the identity $b^nab^{-n}=a^{2^n}$ makes the cyclic subgroup generated by $a$ exponentially distorted.