Automorphisms of doubly-even self-dual binary codes
arXiv:0810.3787 · doi:10.1112/blms/bdp026
Abstract
The automorphism group of a binary doubly-even self-dual code is always contained in the alternating group. On the other hand, given a permutation group of degree there exists a doubly-even self-dual -invariant code if and only if is a multiple of 8, every simple self-dual $\F_2G$-module occurs with even multiplicity in $\F_2^n$, and is contained in the alternating group.
Added a new proof for the main result