Published online by Cambridge University Press: 07 July 2021
We prove a local–global compatibility result in the mod $p$ Langlands program for
$\mathrm {GL}_2(\mathbf {Q}_{p^f})$. Namely, given a global residual representation
$\bar {r}$ appearing in the mod
$p$ cohomology of a Shimura curve that is sufficiently generic at
$p$ and satisfies a Taylor–Wiles hypothesis, we prove that the diagram occurring in the corresponding Hecke eigenspace of mod
$p$ completed cohomology is determined by the restrictions of
$\bar {r}$ to decomposition groups at
$p$. If these restrictions are moreover semisimple, we show that the
$(\varphi ,\Gamma )$-modules attached to this diagram by Breuil give, under Fontaine's equivalence, the tensor inductions of the duals of the restrictions of
$\bar {r}$ to decomposition groups at
$p$.