On Extension Of Functors

A.Chigogidze defined for each normal functor on the category Comp an extension which is a normal functor on the category Tych. We consider this extension for any functor on the category Comp and investigate which properties it preserves from the definition it preserves from the definition of normal functor. We investigate as well some topological properties of such extension

Tambarization of a Mackey functor and its application to the Witt-Burnside construction

For an arbitrary group $G$, a (semi-)Mackey functor is a pair of covariant and contravariant functors from the category of $G$-sets, and is regarded as a $G$-bivariant analog of a commutative (semi-)group. In this view, a $G$-bivariant analog of a (semi-)ring should be a (semi-)Tambara functor. A Tambara functor is firstly defined by Tambara, which he called a TNR-functor, when $G$ is finite. As shown by Brun, a Tambara functor plays a natural role in the Witt-Burnside construction. It will be a natural question if there exist sufficiently many examples of Tambara functors, compared to the wide range of Mackey functors. In the first part of this article, we give a general construction of a Tambara functor from any Mackey functor, on an arbitrary group $G$. In fact, we construct a functor from the category of semi-Mackey functors to the category of Tambara functors. This functor gives a left adjoint to the forgetful functor, and can be regarded as a $G$-bivariant analog of the monoid-ring functor. In the latter part, when $G$ is finite, we invsetigate relations with other Mackey-functorial constructions ---crossed Burnside ring, Elliott's ring of $G$-strings, Jacobson's $F$-Burnside ring--- all these lead to the study of the Witt-Burnside construction.Comment: 31 page