$U_n(q)$ acting on flags and supercharacters

Richard Dipper, Qiong Guo

Let $U=U_n(q)$ be the group of lower unitriangular $n\times n$-matrices with entries in the field ${\mathbb{F}}_q$ with $q$ elements for some prime power $q$ and $n\in \mathbb{N}$. W…