Whittaker supports for representations of reductive groups
[Supports de Whittaker pour les représentations des groupes réductifs]
Annales de l'Institut Fourier, Online first, 48 p.

Soit F le corps , ou une extension finie de p , et soit G une extension centrale finie du groupe des F-points d’un groupe réductif fini sur F. Soit aussi π une representation lisse de G (Fréchet à croissance modérée dans le cas F=). Pour chaque orbite nilpotente 𝒪, on considère un certain quotient de Whittaker π 𝒪 de π. Nous définissons le support de Whittaker WS(π) comme étant l’ensemble des 𝒪 maximales parmi celles pour lesquelles π 𝒪 0.

Dans cet article, nous prouvons que toutes les 𝒪WS(π) sont des orbites nilpotentes quasi-admissibles, généralisant les résultats de Mœglin et de Jiang–Liu–Savin. Si F est p-adique et π est quasi-cuspidale, alors nous montrons que toutes les 𝒪WS(π) sont F-distinguées, c’est-à-dire qu’elles ne rencontrent l’algèbre de Lie d’aucun sous-groupe de Levi de G défini sur F.

Nous donnons aussi une adaptation de nos méthodes aux représentations automorphes, généralisant ainsi des résultats de Ginzburg–Rallis–Soudry, Shen et Cai, et confirmant certaines conjectures de Ginzburg.

Nos méthodes combinent celles des auteurs susmentionnés et de nos propres travaux antérieurs.

Let F be either or a finite extension of p , and let G be a finite central extension of the group of F-points of a reductive group defined over F. Also let π be a smooth representation of G (Fréchet of moderate growth if F=). For each nilpotent orbit 𝒪 we consider a certain Whittaker quotient π 𝒪 of π. We define the Whittaker support WS(π) to be the set of maximal 𝒪 among those for which π 𝒪 0.

In this paper we prove that all 𝒪WS(π) are quasi-admissible nilpotent orbits, generalizing results of Mœglin and Jiang–Liu–Savin. If F is p-adic and π is quasi-cuspidal then we show that all 𝒪WS(π) are F-distinguished, i.e. do not intersect the Lie algebra of any proper Levi subgroup of G defined over F.

We also give an adaptation of our argument to automorphic representations, generalizing results of Ginzburg–Rallis–Soudry, Shen, and Cai, and confirming some conjectures of Ginzburg.

Our methods are a synergy of the methods of the above-mentioned authors, and of our own earlier work.

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DOI : https://doi.org/10.5802/aif.3372
Classification : 20G05,  20G20,  20G25,  20G30,  20G35,  22E27,  22E46,  22E50,  22E55,  17B08
Mots clés : coefficient de Fourier, front d’onde, représentation oscillateur, groupe de Heisenberg, groupe métaplectique, orbite admissible, orbite distinguée, représentation cuspidale, forme automorphe
@unpublished{AIF_0__0_0_A47_0,
     author = {Gomez, Raul and Gourevitch, Dmitry and Sahi, Siddhartha},
     title = {Whittaker supports for representations of reductive groups},
     journal = {Annales de l'Institut Fourier},
     publisher = {Association des Annales de l{\textquoteright}institut Fourier},
     year = {2021},
     doi = {10.5802/aif.3372},
     language = {en},
     note = {Online first},
}
Gomez, Raul; Gourevitch, Dmitry; Sahi, Siddhartha. Whittaker supports for representations of reductive groups. Annales de l'Institut Fourier, Online first, 48 p.

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