Abstract: For a reductive group $G$, its $B_{d}R^{+}$-affine
Grassmannian is defined as the étale (equivalently, v-)
sheafification of the presheaf quotient $LG/L^{+}G$ of the
$B_{d}R$-loop group $LG$ by the $B_{d}R^{+}$-loop subgroup
$L^{+}G$. We...