On integral images of Curtis homomorphisms for ${\mathrm{GL}}_n$ and ${\mathrm{U}}_n$

Abstract

For $G={\mathrm{GL}}_n$ or ${\mathrm{U}}_n$ defined over a finite field of characteristic $p$, we refine a result of Bonnafé and Kessar on the saturatedness of the Curtis homomorphism ${\mathrm{Cur}}^G$ by describing the image of ${\mathrm{Cur}}^G$ over $\overline{\mathbb{Z}}[1/p]$ via a system of linear conditions.

7 pages, minor revision