Beuzart-Plessis, On the spectral decomposition of the Jacquet-Rallis trace formula and the Gan-Gross-Prasad conjecture for unitary groups

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Raphaël Beuzart-Plessis, On the spectral decomposition of the Jacquet-Rallis trace formula and the Gan-Gross-Prasad conjecture for unitary groups.

Reference: Raphaël Beuzart-Plessis, On the spectral decomposition of the Jacquet-Rallis trace formula and the Gan-Gross-Prasad conjecture for unitary groups. BC NT/AG Seminar.

  • Look at automorphic cuspidal representations to \(\operatorname{PGL}_2({ \mathbf{F} })\) for \({ \mathbf{F} }\) a number field.

  • This talk: generalizing some of these formulas:

attachments/image_2021-05-06-14-07-33.png

  • See split torus, quaternion algebra.

  • See cusp forms, period, trace formulas

  • Gan-Gross-Prasad and Ichino-Ikeda conjecture for unitary groups

    • \(E/{ \mathbf{F} }\) a quadratic extension of number fields, so \({ \mathsf{Gal}} (E/{ \mathbf{F} }) \cong {\mathbf{Z}}/2 = \left\{{ 1, c }\right\}\).
    • Take a nondegenerate Hermitian form \(h\) on \(E^n\), define \(U(h)\) as the unitary group of \(h\) and set \(U_h \coloneqq U(h) \times U(h \oplus h_0)\) and \(h_0: E^2 \to E\) where \((x,y) \mapsto xy^c\).
    • Define an L function :

    attachments/image_2021-05-06-14-13-13.png

  • Theorem: from the Langlands philosophy. There is a Hermitian form and a cuspidal representation in the same L packet where \(P\) is nonvanishing .

  • Theorem/conjecture: if \(\sigma\) is tempered everywhere, there is a formula:

    attachments/image_2021-05-06-14-15-00.png

    • See special values of L functions.
  • Proved in special cases.

  • Recent result: \(P_h\neq - \implies L(1/2, \Pi)\neq 0\) proved using twisted automorphic descent.

  • See regularization, Langlands decomposition, Eisenstein series, Levi, GIT quotients, orbital integrals.

    attachments/image_2021-05-06-14-28-57.png

  • Global distributions break into an Euler product of local distributions.

  • Part of proof: use zeta integrals of kernel functions, fix one variable to get a function in a Schwartz space.

    • See unipotent and parabolic subgroups
    • Uses a “standard unfolding” process?
  • See Whittaker function, Petersson inner product, Phragmen-Lindelof principle to control one zeta integral in terms of another.

See Serre’s conjecture.

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