Affine Beilinson-Bernstein localization at the critical level for $\mathrm {GL}_2$

Abstract

We prove the rank 1 case of a conjecture of Frenkel-Gaitsgory: critical level Kac-Moody representations with regular central characters localize onto the affine Grassmannian. The method uses an analogue in local geometric Langlands of the existence of Whittaker models for most representations of $\mathrm {GL}_2$ over a non-Archimedean field.