arXiv subjects

Vladimir Drinfeld

Publications and source records attributed to Vladimir Drinfeld.

At least 19 recordsLinked to original sources

arXiv2026

Character sheaves on unipotent groups in positive characteristic: foundations

In this article we formulate and prove the main theorems of the theory of character sheaves on unipotent groups over an algebraically closed field of characteristic p>0. In particular, we show that every admissible pair for such a group G gives rise to an L-packet of character sheaves on G, and that, conversely, every L-packet of character sheaves on G arises from a (non-unique) admissible pair. In the appendices we discuss two abstract category theory patterns related to the study of character sheaves. The first appendix sketches a theory of duality for monoidal categories, which generalizes the notion of a rigid monoidal category and is close in spirit to the Grothendieck-Verdier duality theory. In the second one we use a topological field theory approach to define the canonical braided monoidal structure and twist on the equivariant derived category of constructible sheaves on an algebraic group; moreover, we show that this category carries an action of the surface operad. The third appendix proves that the "naive" definition of the equivariant constructible derived category with respect to a unipotent algebraic group is equivalent to the "correct" one.

math.RT↗

arXiv2026

On the Lau group scheme

In a 2013 article, Eike Lau constructed a canonical morphism from the stack of $n$-truncated Barsotti-Tate groups over $F_p$ to the stack of $n$-truncated displays. He also proved that this morphism is a gerbe banded by a commutative group scheme. In this paper we describe the group scheme explicitly. The stack of $n$-truncated Barsotti-Tate groups over $F_p$ has a generalization related to any pair $(G,μ)$, where $G$ is a smooth group scheme over $Z/p^n$ and $μ$ is a 1-bounded cocharacter of $G$. The same is true for the stack of $n$-truncated displays. We conjecture that in this more general situation the first stack is a gerbe over the second one banded by a commutative group scheme, and we give a conjectural description of this group scheme. We also give a conjectural description of the stack of $n$-truncated Barsotti-Tate groups over the formal spectrum of $Z_p$ and of its $(G,μ)$-generalization.

math.AG↗

arXiv2026

Ring stacks conjecturally related to the stacks $BT_n^{G,μ}$

Using the ring space of sheared Witt vectors, we define certain ring stacks. We suggest several models for the ring stacks. Motivation: there is a conjectural description of the stack of n-truncated Barsotti-Tate groups and its Shimurian analogs in terms of the new ring stacks.

math.AG↗

arXiv2025

On the quotient of a groupoid by an action of a 2-group

If X is a groupoid equipped with an action of a 2-group G then one has a 2-groupoid X/G. We describe the fibers of the functor from X/G to the 1-groupoid $π_0(X)/π_0(G)$. We also give an explicit model for X/G in a certain situation.

math.CT↗

arXiv2024

A stacky approach to crystals

Inspired by a theorem of Bhatt-Morrow-Scholze, we develop a stacky approach to crystals and isocrystals on "Frobenius-smooth" schemes over F_p . This class of schemes goes back to Berthelot-Messing and contains all smooth schemes over perfect fields of characteristic p. To treat isocrystals, we prove some descent theorems for sheaves of Banachian modules, which could be interesting in their own right.

math.AG↗

arXiv2024

On Shimurian generalizations of the stack $BT_1\otimes F_p$

Let G be a smooth group scheme over $F_p$ equipped with a $G_m$-action such that all weights of $G_m$ on the Lie algebra of G are not greater than 1. Let $Disp_n^G$ be Eike Lau's stack of n-truncated G-displays (this is an algebraic stack over $F_p$). In the case n=1 we introduce an algebraic stack equipped with a morphism to $Disp_1^G$. We conjecture that if G=GL(d) then the new stack is canonically isomorphic to the reduction modulo p of the stack of 1-truncated Barsotti-Tate groups of height d and dimension d', where d' depends on the action of $G_m$ on GL(d). We also discuss how to define an analog of the new stack for n>1 and how to replace $F_p$ by $Z/p^m Z$.

math.AG↗

arXiv2024

Toward Shimurian analogs of Barsotti-Tate groups

We first recall Grothendieck's notion of n-truncated Barsotti-Tate group. Such groups form an algebraic stack over the integers. The problem is to give an illuminating description of its reductions modulo powers of p. A related problem is to construct analogs of these reductions related to general Shimura varieties with good reduction at p. We discuss some conjectures on this subject based on the theory of prismatic cohomology.

math.AG↗

arXiv2024

Prismatization

The goal is to construct three related "prismatization" functors from the category of p-adic formal schemes to that of formal stacks. This should provide a good category of coefficients for prismatic cohomology in the spirit of F-gauges. In this article we define and study the three versions of the prismatization of the formal spectrum of the ring of p-adic integers.

math.AG↗

arXiv2023

A 1-dimensional formal group over the prismatization of Spf Z_p

Let Sigma denote the prismatization of Spf (Z_p). The multiplicative group over Sigma maps to the prismatization of the multiplicative group over Spf (Z_p). We prove that the kernel of this map is the Cartier dual of some 1-dimensional formal group over Sigma. We obtain some results about this formal group (e.g., we describe its Lie algebra). We give a very explicit description of the pullback of the formal group to the quotient of the q-de Rham prism by the action of the multiplicative group of Z_p.

math.AG↗

arXiv2021

On a notion of ring groupoid

By a ring groupoid we mean an animated ring whose i-th homotopy groups are zero for all i>1. In this expository note we give an elementary treatment of the (2,1)-category of ring groupoids (i.e., without referring to general animated rings and without using n-categories for n>2). The note is motivated by the fact that ring stacks play a central role in the Bhatt-Lurie approach to prismatic cohomology.

math.CT↗

arXiv2020

On a theorem of Scholze-Weinstein

Let G be the Tate module of a p-divisble group H over a perfect field k of characteristic p. A theorem of Scholze-Weinstein describes G (and therefore H itself) in terms of the Dieudonne module of H; more precisely, it describes G(C) for "good" semiperfect k-algebras C (which is enough to reconstruct G). In these notes we give a self-contained proof of this theorem and explain the relation with the classical descriptions of the Dieudonne functor from Dieudonne modules to p-divisible groups.

math.AG↗

arXiv2019

Grinberg-Kazhdan theorem and Newton groupoids

We first prove the Grinberg-Kazhdan formal arc theorem without any assumptions on the characteristic. This part of the article is equivalent to arXiv:math-AG/0203263. Then we try to clarify the geometric ideas behind the proof by introducing the notion of Newton groupoid (which is related to Newton's method for finding roots). Newton groupoids are certain groupoids in the category of schemes associated to any generically etale morphism from a locally complete intersection to a smooth variety.

math.AG↗

arXiv2018

Slopes of indecomposable F-isocrystals

We prove that for an indecomposable convergent or overconvergent F-isocrystal on a smooth irreducible variety over a perfect field of characteristic p, the gap between consecutive slopes at the generic point cannot exceed 1. (This may be thought of as a crystalline analogue of the following consequence of Griffiths transversality: for an indecomposable variation of complex Hodge structures, there cannot be a gap between nonzero Hodge numbers.) As an application, we deduce a refinement of a result of V.Lafforgue on the slopes of Frobenius of an l-adic local system. We also prove similar statements for G-local systems (crystalline and l-adic ones), where G is a reductive group. We translate our results on local systems into properties of the p-adic absolute values of the Hecke eigenvalues of a cuspidal automorphic representation of a reductive group over the adeles of a global field of characteristic p>0.

math.AG↗

arXiv2018

On a conjecture of Deligne

Let X be a smooth variety over $F_p$. Let E be a number field. For each nonarchimedean place $λ$ of E prime to p consider the set of isomorphism classes of irreducible lisse $\bar{E}_λ$-sheaves on X with determinant of finite order such that for every closed point x in X the characteristic polynomial of the Frobenius $F_x$ has coefficents in E. We prove that this set does not depend on $λ$. The idea is to use a method developed by G.Wiesend to reduce the problem to the case where X is a curve. This case was treated by L. Lafforgue.

math.NT↗

arXiv2018

On the pro-semisimple completion of the fundamental group of a smooth variety over a finite field

Let $Π$ be the fundamental group of a smooth variety X over $F_p$. Given a non-Archimedean place $λ$ of the field of algebraic numbers which is prime to p, consider the $λ$-adic pro-semisimple completion of $Π$ as an object of the groupoid whose objects are pro-semisimple groups and whose morphisms are isomorphisms up to conjugation by elements of the neutral connected component. We prove that this object does not depend on $λ$. If dim X=1 we also prove a crystalline generalization of this fact. We deduce this from the Langlands conjecture for function fields (proved by L. Lafforgue) and its crystalline analog (proved by T. Abe) using a reconstruction theorem in the spirit of Kazhdan-Larsen-Varshavsky. We also formulate two related conjectures, each of which is a "reciprocity law" involving a sum over all $l$-adic cohomology theories (including the crystalline theory for $l=p$).

math.NT↗

arXiv2016

On a strange invariant bilinear form on the space of automorphic forms

Let F be a global field and A its ring of adeles. Let G:=SL(2). We study the bilinear form B on the space of K-finite smooth compactly supported functions on G(A )/G(F) defined by the formula B (f,g):=B'(f,g)-(M^{-1}CT (f),CT (g)), where B' is the usual scalar product, CT is the constant term operator, and M is the standard intertwiner. This form is natural from the viewpoint of the geometric Langlands program. To justify this claim, we provide a dictionary between the classical and "geometric" theory of automorphic forms. We also show that the form B is related to S. Schieder's Picard-Lefschetz oscillators.

math.NT↗

arXiv2015

Compact generation of the category of D-modules on the stack of G-bundles on a curve

The goal of the paper is to show that the (derived) category of D-modules on the stack Bun_G(X) is compactly generated. Here X is a smooth complete curve, and G is a reductive group. The problem is that Bun_G(X) is not quasi-compact, so the above compact generation is not automatic. The proof is based on the following observation: Bun_G(X) can be written as a union of quasi-compact open substacks, which are "co-truncative", i.e., the j_! extension functor is defined on the entire category of D-modules.

math.AG↗

arXiv2015

On algebraic spaces with an action of G_m

Let Z be an algebraic space of finite type over a field, equipped with an action of the multiplicative group $G_m$. In this situation we define and study a certain algebraic space equipped with an unramified morphism to $A^1\times Z\times Z$, where $A^1$ is the affine line. (If Z is affine and smooth this is just the closure of the graph of the action map $G_m\times Z\to Z$.) In articles joint with D.Gaitsgory we use this set-up to prove a new result in the geometric theory of automorphic forms and to give a new proof of a very important theorem of T. Braden.

math.AG↗