In the first paper in this series a structure S was called canonically reconstructible from a structure T provided 5 was canonically isomorphic to a structure T' derived from T. The principle proposition of the paper was the scholium which asserted: If a structure 5 contains a substructure T and if S is canonically reconstructible from T, then every automorphism of T may be extended uniquely to...

Introduction. The inner automorphism of an element g of a group G is denoted by ig and is given by the formula xig = gxg−1 for all x ∈ G. The mapping π : G→Aut(G), taking each g∈G to the inner automorphism ig, is a homomorphism, Ker(π) = Z(G) and Im(π) = Inn(G). It is easy to check that the automorphism group Aut(G) of a group G with trivial center also is a group with trivial center. Therefore...

The description of the automorphism group of group 〈a, b; [am, bn] = 1〉 (m, n > 1) in terms of generators and defining relations is given. This result is applied to prove that any normal automorphism of every such group is inner. 2000 Mathematics Subject Classification: primary 20F28, 20F05; secondary 20E06.

Let Mod(S) be the extended mapping class group of a surface S. For S the twice-punctured torus, we show that there exists an isomorphism of finite index subgroups of Mod(S) which is not the restriction of any inner automorphism. For S a torus with at least three punctures, we show that every injection of a finite index subgroup of Mod(S) into Mod(S) is the restriction of an inner automorphism o...

In functional analysis, approximative properties of an object become precise in its ultrapower. We discuss this idea and its consequences for automorphisms of II1 factors. Here are some sample results: (1) an automorphism is approximately inner if and only if its ultrapower is א0-locally inner; (2) the ultrapower of an outer automorphism is always outer; (3) for unital *-homomorphisms from a se...

Let p be a prime,G a finite group which has a normal p-subgroup containing its own centralizer inG, and R a commutative local ring with residue class field of characteristic p. In this paper, it is shown that if α is an augmented automorphism of RG which fixes a Sylow p-subgroup P of G, there is ρ ∈ Aut(G) such that xαρ = x for all x ∈ P , and αρ is an inner automorphism of RG.