On the automorphism group of various Goppa codes

Abstract

We determine the automorphism group of various Goppa codes /spl Cscr//sub L/(D,G) associated with certain function fields F/F/sub q/ of genus g>0. It is well known that, for deg D=n>2g+2, the automorphism group {Aut/sub D,G/(F/F/sub q/) can be embedded into Aut(/spl Cscr//sub L/(D,G)) as a subgroup. We show that, under certain conditions on the divisors D and G Aut/sub D,G/(F/F/sub q/) is actually isomorphic to Aut(/spl Cscr//sub L/(D,G)).