Using Sigma theory we show that for large classes of groups G there is a subgroup H of finite index in Aut(G) such that for phi is an element of H the Reidemeister number R(phi) is infinite. This includes all finitely ...

Special groups are an axiomatization of the algebraic theory of quadratic forms over fields. It is known that any finite reduced special group is the special group of some field. We show that any special group that is the ...

The objective of this work is to study the techniques developed in the theory of blocks for finite groups and then, using the machinery of profinite groups and results from the modular representation theory of profinite ...

We will give three characterizations of such fields and an application to quadratic forms in characteristic 2.