Logarithmable automorphism

From Groupprops

Definition

Suppose is a non-associative ring and is an automorphism of . Suppose further that:

  1. is locally nilpotent, i.e., for every , there exists a natural number , possibly dependent upon , such that .
  2. is an infinitely powered endomorphism of the additive structure of , i.e., for all natural numbers , is powered for all primes less than or equal to .
  3. The logarithm of , which can be defined because of (1) and (2), is a derivation of .

We then say that is a logarithmabl automorphism of .