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On mod
$p$ local-global compatibility for
$\text{GL}_{3}$ in the ordinary case
Published online by Cambridge University Press: 25 August 2017
Abstract
Suppose that $F/F^{+}$ is a CM extension of number fields in which the prime
$p$ splits completely and every other prime is unramified. Fix a place
$w|p$ of
$F$. Suppose that
$\overline{r}:\operatorname{Gal}(\overline{F}/F)\rightarrow \text{GL}_{3}(\overline{\mathbb{F}}_{p})$ is a continuous irreducible Galois representation such that
$\overline{r}|_{\operatorname{Gal}(\overline{F}_{w}/F_{w})}$ is upper-triangular, maximally non-split, and generic. If
$\overline{r}$ is automorphic, and some suitable technical conditions hold, we show that
$\overline{r}|_{\operatorname{Gal}(\overline{F}_{w}/F_{w})}$ can be recovered from the
$\text{GL}_{3}(F_{w})$-action on a space of mod
$p$ automorphic forms on a compact unitary group. On the way we prove results about weights in Serre’s conjecture for
$\overline{r}$, show the existence of an ordinary lifting of
$\overline{r}$, and prove the freeness of certain Taylor–Wiles patched modules in this context. We also show the existence of many Galois representations
$\overline{r}$ to which our main theorem applies.
- Type
- Research Article
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- Copyright
- © The Authors 2017
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