Bruhat decomposition of SL2 over a finite field (source code)

= Bruhat decomposition of SL2 over a finite field
{c}

This is the finite special-linear-group instance of the general <Bruhat decomposition>.

For the upper-triangular subgroup $B$ of $SL_2(\mathbb F_p)$ and
$$
w=\begin{pmatrix}0&-1\\1&0\end{pmatrix},
$$
the two double cosets are $B$ and $BwB$, and $B\cap wBw^{-1}=T$, the diagonal subgroup.