Multiplicatively cohomological Tambara functors

Abstract

We study a nice class of Tambara functors, called multiplicatively cohomological Tambara functors. The first result is a proof of a conjecture of Balchin, Quigley, and Spitz showing that every multiplicatively cohomological Tambara functor is also additively cohomological. Building on this, we prove Nakayama's lemma for multiplicatively cohomological Tambara functors. As an application, we identify a condition under which finitely generated projective modules over local Tambara functors are always free. This applies, in particular, to the constant $C_{p^n}$-Tambara functor $\underline{\mathbb{Z}}_p$.