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44 votes
4 answers
3k views

Are there motives which do not, or should not, show up in the cohomology of any Shimura variety?

Let $F$ be a real quadratic field and let $E/F$ be an elliptic curve with conductor 1 (i.e. with good reduction everywhere; these things can and do exist) (perhaps also I should assume E has no CM, ...
Kevin Buzzard's user avatar
16 votes
3 answers
2k views

Constructing coherent sheaves on Shimura varieties.

Let me first run through the setting of my question in an example I understand well; that of modular curves. If $Y_1(N)$ denotes the usual modular curve over the complexes, the quotient of the upper ...
Kevin Buzzard's user avatar
13 votes
1 answer
2k views

Which Shimura varieties are known to be automorphic?

This seems like something that should be well-known, but as an outsider to the field, I'm having trouble locating precise statements. Hasse-Weil zeta functions of Shimura varieties should be ...
B R's user avatar
  • 3,183
11 votes
1 answer
786 views

A frustrating cohomology class on the moduli of abelian surfaces

Here's a very frustrating question that I have been stuck on for some time. I believe that my question could fit in a general framework of what happens when you restrict $L^2$-cohomology classes on a ...
Dan Petersen's user avatar
  • 40.2k
10 votes
1 answer
392 views

Matsushima-Murakami Isomorphism for $L^2$-cohomology

Let $\mathbf{G}$ be a reductive connected linear algebraic group over a totally real global number field, say $\mathbb{Q}$. Let $\mathbb{A}=\mathbb{R}\times\mathbb{A}_f$ be the ring of rational adele. ...
Mirko's user avatar
  • 203
9 votes
2 answers
1k views

modularity of algebraic varieties

Hello, Are there any examples of varieties which are not Shimura varieties or abelian varieties and whose L-functions have been shown to be a product of automorphic L-functions? Thanks. N
Nicolás's user avatar
  • 2,842
6 votes
0 answers
265 views

drinfeld shtukas over higher dimensional spaces

Everytime I encounter Drinfeld Shtukas, the definition begins with vector bundles over a curve $X$ over a finite field. My question is: why the restriction to curves? Is there any interest or results ...
usr0192's user avatar
  • 785
6 votes
0 answers
339 views

Is there an integral pairing between quaternionic Hecke algebras and cusp forms?

Let $F$ be a totally real number field with integers $\mathcal{O}_F$ and $B$ a quaternion algebra over $F$ split at exactly one infinity place.Fix $n\geq 1$ and like in the special case $F=\mathbb{Q}, ...
Konrad's user avatar
  • 469
5 votes
1 answer
365 views

modularity lifting theorems for non-compact unitary groups

I am reading David Geraghty's paper, 'Modularity lifting theorems for ordinary Galois representations'(https://link.springer.com/article/10.1007/s00208-018-1742-4) and I have a related question, which,...
Zhan's user avatar
  • 63
5 votes
0 answers
163 views

Uniqueness of cohomological holomorphic discrete series representation

In Claus Sorenson's PhD thesis, he proves a theorem about level lifting of paramodular forms whose associated automorphic representation has component $\pi_{\infty}$ that is the "cohomological ...
Watson Ladd's user avatar
  • 2,429
5 votes
0 answers
681 views

Base change and Langlands' combinatorial exercise

Is it correct that Langlands' combinatorial exercise (as he terms it in his paper "Shimura varieties and the Selberg trace formula") is to establish base change identities between orbital integrals of ...
Nicolás's user avatar
  • 2,842
4 votes
0 answers
191 views

Several L-functions but one Galois representation: How to choose

Let $\mathbf{G}$ be a reductive group which enjoys all the nice properties a reducive group can dream of. Fix $(\mathbf{G},X)$ a Shimura datum associated with it and assume that if $K\leq\mathbf{G} $ ...
Marsault Chabat's user avatar
4 votes
0 answers
206 views

Higher dimensional generalization of an identity between traces of Hecke operators and number of elliptic curves over finite fields?

In http://www.math.ubc.ca/~behrend/ladic.pdf, the author uses his generalization of Lefschetz trace formula to smooth algebraic stacks to prove an interesting identity (Proposition 6.4.11.): $\sum_{k}...
Zhiyu's user avatar
  • 6,622
2 votes
0 answers
201 views

Shintani's unpublished paper on automorphic forms

I'm trying to find Shintani's preprint: Shintani T., On automorphic forms on unitary groups of order 3, unpublished, 1979. It seems to be impossible to find, even though several authors quote it. I ...
Fra's user avatar
  • 91
1 vote
0 answers
125 views

When is a vector bundle on a Shimura variety an automorphic vector bundle?

Let $(G, X)$ be a Shimura datum, let $K \subset G(\mathbb{A}_f)$ be an open compact subgroup, and denote by $\text{Sh}_K(G,X)$ the Shimura variety whose complex points are given by $G(\mathbb{Q})\...
ChimiSeanGa's user avatar
1 vote
0 answers
136 views

Notion of "Hodge bundle" for abelian type Shimura varieties

For a Siegel type Shimura datum $(\text{GSp}_{2g}, \mathcal{H}^{\pm})$ and level $K$, we construct the Shimura variety $S_{g,K} := \text{Sh}_K(\text{GSp}_{2g},\mathcal{H}^{\pm})$. We have a universal ...
ChimiSeanGa's user avatar