Fourier coefficients of automorphic forms, character variety orbits, and small representations

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Text: We consider the Fourier expansions of automorphic forms on general Lie groups, with a particular emphasis on exceptional groups. After describing some principles underlying known results on GL(n), Sp(4), and G 2, we perform an analysis of the expansions on split real forms of E 6 and E 7 where simplifications take place for automorphic realizations of real representations which have small Gelfand-Kirillov dimension. Though the character varieties are more complicated for exceptional groups, we explain how the nonvanishing Fourier coefficients for small representations behave analogously to Fourier coefficients on GL(n). We use this mechanism, for example, to show that the minimal representation of either E 6 or E 7 never occurs in the cuspidal automorphic spectrum. We also give a complete description of the internal Chevalley modules of all complex Chevalley groups - that is, the orbit decomposition of the Levi factor of a maximal parabolic on its unipotent radical. This generalizes classical results on trivectors and in particular includes a full description of the complex character variety orbits for all maximal parabolics. The results of this paper have been applied in the string theory literature to the study of BPS instanton contributions to graviton scattering (Green et al., 2011, [12]). Video: For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=ELkyOT8c28I.

Original languageEnglish (US)
Pages (from-to)3070-3108
Number of pages39
JournalJournal of Number Theory
Volume132
Issue number12
DOIs
StatePublished - Dec 1 2012

Fingerprint

Character Variety
Automorphic Forms
Fourier coefficients
Orbit
Gelfand-Kirillov Dimension
Chevalley Groups
Fourier Expansion
Instantons
String Theory
Simplification
Scattering
Internal
Decompose
Module
Generalise

All Science Journal Classification (ASJC) codes

  • Algebra and Number Theory

Keywords

  • Adjoint action
  • Automorphic forms
  • Character variety orbits
  • Exceptional groups
  • Fourier expansions
  • Internal Chevalley modules
  • Small representations
  • Wavefront set
  • Whittaker models

Cite this

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title = "Fourier coefficients of automorphic forms, character variety orbits, and small representations",
abstract = "Text: We consider the Fourier expansions of automorphic forms on general Lie groups, with a particular emphasis on exceptional groups. After describing some principles underlying known results on GL(n), Sp(4), and G 2, we perform an analysis of the expansions on split real forms of E 6 and E 7 where simplifications take place for automorphic realizations of real representations which have small Gelfand-Kirillov dimension. Though the character varieties are more complicated for exceptional groups, we explain how the nonvanishing Fourier coefficients for small representations behave analogously to Fourier coefficients on GL(n). We use this mechanism, for example, to show that the minimal representation of either E 6 or E 7 never occurs in the cuspidal automorphic spectrum. We also give a complete description of the internal Chevalley modules of all complex Chevalley groups - that is, the orbit decomposition of the Levi factor of a maximal parabolic on its unipotent radical. This generalizes classical results on trivectors and in particular includes a full description of the complex character variety orbits for all maximal parabolics. The results of this paper have been applied in the string theory literature to the study of BPS instanton contributions to graviton scattering (Green et al., 2011, [12]). Video: For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=ELkyOT8c28I.",
keywords = "Adjoint action, Automorphic forms, Character variety orbits, Exceptional groups, Fourier expansions, Internal Chevalley modules, Small representations, Wavefront set, Whittaker models",
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Fourier coefficients of automorphic forms, character variety orbits, and small representations. / Miller, Stephen; Sahi, Siddhartha.

In: Journal of Number Theory, Vol. 132, No. 12, 01.12.2012, p. 3070-3108.

Research output: Contribution to journalArticle

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N2 - Text: We consider the Fourier expansions of automorphic forms on general Lie groups, with a particular emphasis on exceptional groups. After describing some principles underlying known results on GL(n), Sp(4), and G 2, we perform an analysis of the expansions on split real forms of E 6 and E 7 where simplifications take place for automorphic realizations of real representations which have small Gelfand-Kirillov dimension. Though the character varieties are more complicated for exceptional groups, we explain how the nonvanishing Fourier coefficients for small representations behave analogously to Fourier coefficients on GL(n). We use this mechanism, for example, to show that the minimal representation of either E 6 or E 7 never occurs in the cuspidal automorphic spectrum. We also give a complete description of the internal Chevalley modules of all complex Chevalley groups - that is, the orbit decomposition of the Levi factor of a maximal parabolic on its unipotent radical. This generalizes classical results on trivectors and in particular includes a full description of the complex character variety orbits for all maximal parabolics. The results of this paper have been applied in the string theory literature to the study of BPS instanton contributions to graviton scattering (Green et al., 2011, [12]). Video: For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=ELkyOT8c28I.

AB - Text: We consider the Fourier expansions of automorphic forms on general Lie groups, with a particular emphasis on exceptional groups. After describing some principles underlying known results on GL(n), Sp(4), and G 2, we perform an analysis of the expansions on split real forms of E 6 and E 7 where simplifications take place for automorphic realizations of real representations which have small Gelfand-Kirillov dimension. Though the character varieties are more complicated for exceptional groups, we explain how the nonvanishing Fourier coefficients for small representations behave analogously to Fourier coefficients on GL(n). We use this mechanism, for example, to show that the minimal representation of either E 6 or E 7 never occurs in the cuspidal automorphic spectrum. We also give a complete description of the internal Chevalley modules of all complex Chevalley groups - that is, the orbit decomposition of the Levi factor of a maximal parabolic on its unipotent radical. This generalizes classical results on trivectors and in particular includes a full description of the complex character variety orbits for all maximal parabolics. The results of this paper have been applied in the string theory literature to the study of BPS instanton contributions to graviton scattering (Green et al., 2011, [12]). Video: For a video summary of this paper, please click here or visit http://www.youtube.com/watch?v=ELkyOT8c28I.

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