Abstract:
Given an object X of a category C, a Beck module for X is an
abelian group object in the slice category C/X. For a ring R, it is a
2-sided R-module; for a group G, it is a right G-module; for a
commutative ring R, it is just an R-module; for a Lie algebra L it is
the usual notion of L-module. These depend on the ambient category of
course. But when a student in Paris named Leonard Guetta asked me
what was a Beck module for a monoid, I assumed it was an ordinary
module. But I was wrong. I will describe what it actually is.