The reciprocal of the beta function and GL(n,ℝ) Whittaker functions
Stade, Eric
Annales de l'Institut Fourier, Tome 44 (1994), p. 93-108 / Harvested from Numdam
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Dans cet article nous obtenons, à l’aide du théorème de la sommation de Gauss pour les séries hypergéométriques, une expression intégrale très simple pour l’inverse de la fonction beta d’Euler. Cette expression est semblable dans sa forme à plusieurs intégrales bien connues de la fonction beta proprement dite.

Nous appliquons ensuite notre nouvelle formule aux fonctions de Whittaker pour les groupes GL(n,ℝ). Ces dernières sont des fonctions spéciales que l’on retrouve dans la théorie de Fourier appliquée aux formes automorphes du groupe linéaire général. Plus précisément, nous déduisons des représentations intégrales explicites pour les fonctions “fondamentales” de Whittaker pour les cas GL(3,ℝ) et GL(4,ℝ). Les intégrales ainsi obtenues sont très semblables aux intégrales connues des fonctions “classe-première” de Whittaker sur ces groupes. Nous croyons que cette correspondance entre les expressions des différents types de fonctions de Whittaker, pourra s’étendre aux groupes de rang arbitraire.

In this paper we derive, using the Gauss summation theorem for hypergeometric series, a simple integral expression for the reciprocal of Euler’s beta function. This expression is similar in form to several well-known integrals for the beta function itself.

We then apply our new formula to the study of GL(n,ℝ) Whittaker functions, which are special functions that arise in the Fourier theory for automorphic forms on the general linear group. Specifically, we deduce explicit integral representations of “fundamental” Whittaker functions for GL(3,ℝ) and GL(4,ℝ). The integrals obtained are seen to resemble very closely known integrals for the “class-one” Whittaker functions on these groups. It is expected that this correspondence between expressions for different types of Whittaker functions will carry over to groups of arbitrary rank.

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     author = {Stade, Eric},
     title = {The reciprocal of the beta function and $GL(n, {\mathbb {R}})$ Whittaker functions},
     journal = {Annales de l'Institut Fourier},
     volume = {44},
     year = {1994},
     pages = {93-108},
     doi = {10.5802/aif.1390},
     mrnumber = {96h:11046},
     zbl = {0801.33001},
     language = {en},
     url = {http://dml.mathdoc.fr/item/AIF_1994__44_1_93_0}
}

Stade, Eric. The reciprocal of the beta function and $GL(n, {\mathbb {R}})$ Whittaker functions. Annales de l'Institut Fourier, Tome 44 (1994) pp. 93-108. doi : 10.5802/aif.1390. http://gdmltest.u-ga.fr/item/AIF_1994__44_1_93_0/

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