On exceptional rigid local systems

Rationally isotropic exceptional projective homogeneous varieties are locally isotropic

Assume that R is a local regular ring containing an infinite perfect field, or that R is the local ring of a point on a smooth scheme over an infinite field. Let K be the field of fractions of R and the characteristic of K is not 2. Let X be an exceptional projective homogeneous scheme over R. We prove that in most cases the condition that X has a K-point implies that X has an R-point.

Generalized Kuga-Satake theory and rigid local systems, II: rigid Hecke eigensheaves

This paper uses rigid Hecke eigensheaves, building on Yun's work on the construction of motives with exceptional Galois groups, to produce the first robust examples of `generalized Kuga-Satake theory' outside the Tannakian category of motives generated by abelian varieties. To strengthen our description of the `motivic' nature of Kuga-Satake lifts, we digress to establish a result that should be of independent interest: for any quasi-projective variety over a (finitely-generated) characteristic zero field, the associated weight-graded of its intersection cohomology arises from a motivated moti…

Local Fourier transforms and rigidity for D-modules

Local Fourier trnasforms, analogous to the $\ell$-adic Fourier transforms, are constructed for connections over $k((t))$. Following a program of Katz, a meromorphic connection on a curve is shown to be rigid, i.e. determined by local data at the singularities, if and only if a certain cohomological condition is satisfied. We show that the index of rigidity is invariant under Fourier transform.

Rigid Local Systems and Weighted Homogeneous Curves

We introduce a notion of rigid local system on the comple- ment of a plane curve $Y$, which relies on a canonical Waldhausen de- composition of the Milnor sphere associated to $Y$. We show that when $Y$ is weigthed homogeneous this notion is deeply related to the classical notion of rigidity on the Riemann sphere. We construct large families of rigid local systems on the complement of weighted homogeneous plane curves and show that the corresponding $D$-modules are generated by `special' multivalued holomorphic functions.

Rational rigidity for E_8(p)

We prove the existence of certain rationally rigid triples E8 in good characteristic and thereby show that these groups over the prime field occur as Galois groups over the field of rational numbers. We show that these triples give rise to rigid triples in the algebraic group and prove that they generate an interesting subgroup in characteristic 0. As a byproduct we derive a remarkable symmetry between the character table of a finite reductive group and that of its dual group. We also give a classification of possible overgroups in exceptional groups containing regular unipotent elements.

Rigid local systems and potential automorphy: The $G_2$-case

We use a certain rigid local system in order to prove the potential automorphy of certain Galois representations with values in $G_2,$ found by N. Katz and the author.

例外 Shimura 簇的积分典范模型

Integral canonical models of exceptional Shimura varieties

本文证明例外 Shimura 簇在足够大的素数处存在积分典范模型，并推广至周期映射像，进而得到若干算术推论。

Rigid local systems and relative motives with Galois group G_2

We classify rigid local systems of rank 7 whose monodromy group is dense in the simple algebraic group of type G2. This leads to motives with Galois group G2.

某些例外Shimura变种嵌入到Siegel模变种中

Embeddings of Certain Exceptional Shimura Varieties into Siegel Modular Varieties

本文定义了一类包含某些例外群局部Shimura变种的局部Shimura变种，并为该类构建了从(G, μ)-显示到p-可除群的函子。作为应用，证明了对于该类，局部Shimura变种在无穷级可代表且完美oid。考虑该类的全局对应物，将某些例外Shimura变种嵌入到Siegel模变种中。特别是，证明它们在无穷级是完美oid。

Generalized Kuga-Satake theory and rigid local systems, I: the middle convolution

This note explains an approach to producing examples of 'generalized Kuga-Satake theory' based on establishing special cases of Simpson's conjecture that rigid local systems are motivic. This strategy is then carried out, using work of Bogner and Reiter, in a low-dimensional example, producing the first non-trivial examples of generalized Kuga-Satake theory outside of the Tannakian category of motives generated by abelian varieties. For a more robust collection of examples, see the sequel "Generalized Kuga-Satake theory and rigid local systems, II: rigid Hecke eigensheaves."

G-rigid local systems are integral

Let $G$ be a reductive group, and let $X$ be a smooth quasi-projective complex variety. We prove that any $G$-irreducible, $G$-cohomologically rigid local system on $X$ with finite order abelianization and quasi-unipotent local monodromies is integral. This generalizes work of Esnault and Groechenig when $G= \mathrm{GL}_n$, and it answers positively a conjecture of Simpson for $G$-cohomologically rigid local systems. Along the way we show that the connected component of the Zariski-closure of the monodromy group of any such local system is semisimple.

On the equidistribution of totally geodesic submanifolds in compact locally symmetric spaces and application to boundedness results for negative curves and exceptional divisors

We prove an equidistribution result for totally geodesic submanifolds in a compact locally symmetric space. In the case of Hermitian locally symmetric spaces, this gives a convergence theorem for currents of integration along totally geodesic subvarieties. As a corollary, we obtain that on a complex surface which is a compact quotient of the bidisc or of the 2-ball, there is at most a finite number of totally geodesic curves with negative self intersection. More generally, we prove that there are only finitely many exceptional totally geodesic divisors in a compact Hermitian locally symmetric …

On symplectically rigid local systems of rank four and Calabi-Yau operators

We classify all $\Sp_4(\mathbb{C})$-rigid, quasi-unipotent local systems and show that all of them have geometric origin. Furthermore, we investigate which of those having a maximal unipotent element are induced by fourth order Calabi-Yau operators. Via this approach, we reconstruct all known Calabi-Yau operators inducing a $\Sp_4(\mathbb{C})$-rigid monodromy tuple and obtain closed formulae for special solutions of them.

Epsilon local rigidity and numerical algebraic geometry

A well-known combinatorial algorithm can decide generic rigidity in the plane by determining if the graph is of Pollaczek-Geiringer-Laman type. Methods from matroid theory have been used to prove other interesting results, again under the assumption of generic configurations. However, configurations arising in applications may not be generic. We present Theorem 5 and its corresponding Algorithm 1 which decide if a configuration is epsilon-locally rigid, a notion we define. A configuration which is epsilon-locally rigid may be locally rigid or flexible, but any continuous deformations remain wi…

Rigidity in automorphic representations and local systems

We introduce the notion of rigidity for automorphic representations of groups over global function fields. We construct the Langlands parameters of rigid automorphic representations explicitly as local systems over open curves. We expect these local systems to be rigid. Examples of rigid automorphic representations from previous work are reviewed and more examples for $GL_{2}$ are discussed in details.

motivic local system 的 exceptional locus

The exceptional locus of a motivic local system

本文研究了motivic local system的exceptional locus，定义了其作为衡量motivic复杂度变化的方式，并证明了其为可数个闭合代数子簇的并集，扩展了André的纯情况结果。

Picard 数为二的射影光滑 horospherical 变种的局部刚性

Local rigidity of projective smooth horospherical varieties of Picard number two

研究 Picard 数为二的射影光滑 horospherical 变种的局部刚性，基于先前工作中的自同构群计算结果。

Desingularization algorithms I. Role of exceptional divisors

The article is about a "desingularization principle" common to various canonical desingularization algorithms in characteristic zero, and the roles played by the exceptional divisors in the underlying local construction. We compare algorithms of the authors and of Villamayor and his collaborators, distinguishing between the fundamental effect of the way the exceptional divisors are used, and different theorems obtained because of flexibility allowed in the choice of "input data". We show how the meaning of "invariance" of the desingularization invariant, and the efficiency of the algorithm dep…

On the action of the Weil group on the l-adic cohomology of rigid spaces over local fields

We investigate the action of the Weil group on the compactly supported l-adic cohomology groups of rigid spaces over local fields. We prove that every eigenvalue of the action is a Weil number when either a rigid space is smooth or the characteristic of the base field is equal to 0. Since a smooth rigid space is locally isomorphic to the Raynaud generic fiber of an algebraizable formal scheme, we can use the techniques of alterations and monodromy spectral sequences in the smooth case. In the general case, we use the continuity theorem of Huber, which requires the restriction on the characteri…

Finiteness of cohomology of local systems on rigid analytic spaces

We prove that the cohomology groups of an etale Q_p-local system on a smooth proper rigid analytic space are finite-dimensional Q_p-vector spaces, provided that the base field is either a finite extension of Q_p or an algebraically closed nonarchimedean field containing Q_p. This result manifests as a special case of a more general finiteness result for the higher direct images of a relative (phi, Gamma)-module along a smooth proper morphism of rigid analytic spaces over a mixed-characterstic nonarchimedean field.

Rigid local systems with monodromy group the Conway group Co_3

We first develop some basic facts about certain sorts of rigid local systems on the affine line in characteristic $p>0$. We then apply them to exhibit a number of rigid local systems of rank $23$ on the affine line in characteristic $p=3$ whose arithmetic and geometric monodromy groups are the Conway group $\mathrm{Co}_3$ in its orthogonal irreducible representation of degree $23$.

覆盖构造的局部刚性与曲线模空间的Weil–Petersson子簇

Local rigidity of covering constructions and Weil--Petersson subvarieties of the moduli space of curves

本文证明了曲线模空间$\u039c_{g,n}$的Weil–Petersson全测地子簇及覆盖构造是局部刚性的，该结论由一类轨形映射的一般刚性结果推导得到。