We introduce conditions on a group action on a tree that are sufficient for the action to extend to the automorphism group. We apply this to two different classes of one-relator groups: certain Baumslag-Solitar groups and one-relator groups with centre. In each case we derive results about the automorphism group, and deduce that there are relatively few outer automorphisms.
|Number of pages||11|
|Journal||Journal of Group Theory|
|Publication status||Published - 2000|