Magnus Carlson: Plethories and actions on rings

If R is a commutative ring, one can define a plethory to be a comonoid object in the category of affine R-algebra schemes. Following Borger-Wieland's paper on plethories I will introduce plethories and talk about the ring of big Witt vectors as a motivating example. Towards the end of the talk I will sketch some hints of further generalizations of the concept which might be useful.