Among the bounty of brilliancies bequeathed to humanity by Srinivasa Ramanujan, the circle method and the notion of mock theta functions strike wonder and spark intrigue in number theorists fresh and seasoned alike. The former creation was honed to perfection for its original purpose of counting partitions by Hans Rademacher. The latter ingenuity, despite receiving considerable scrutiny, remained largely enigmatic for decades. In 2002 Sander Zwegers ascertained the essential properties characterizing Ramanujan's mock theta functions.

Picard moduli spaces parametrize principally polarized abelian varieties with complex multiplication by the ring of integers in an imaginary-quadratic field. The loci where the abelian varieties split off an elliptic curve in a controlled way are divisors on this moduli space. We study the intersection behaviour of these divisors and prove in the non-degenerate case a relation between their intersection numbers and Fourier coefficients of the derivative at s=0 of a certain incoherent Eisenstein series for the unitary group. This is joint work with Kudla.

GALOIS REPRESENTATIONS AND AUTOMORPHIC FORMS SEMINAR

We shall recall the spectral terms from the trace formula for G and its stabilaization, as well as corresponding terms from the twisted trace formula for GL(N). We shall then discuss aspects of the proof of the theorems stated in the first talk that are related to the comparison of these formulas.

GALOIS REPRESENTATIONS AND AUTOMORPHIC FORMS SEMINAR

Suppose that G is a connected, quasisplit, orthogonal or symplectic group over a field F of characteristic 0. We shall describe a classification of the irreducible representations of G(F) if F is local, and the automorphic representations of G in the discrete spectrum if F is global. The classification is by harmonic analysis and endoscopic transfer, which ultimately ties the representations of G to those of general linear groups.

March 21-25,2011

http://www.math.ias.edu/sp/graf

GALOIS REPRESENTATIONS AND AUTOMORPHIC FORMS SEMINAR

Note: (joint work with O. Brinon and A. Mokrane)

http://math.ias.edu/files/seminars/GriffithsTwoTalks.pdf

GALOIS REPRESENTATIONS AND AUTOMORPHIC FORMS SEMINAR

Some automorphic forms, despite the fact they are algebraic, do not have any interpretation as cohomology classes on a Shimura variety: therefore nothing is known at present on their expected arithmetic properties. I shall explain how such forms appear to be related to more general objects (Griffiths-Schmid varieties) and discuss some related rationality questions.