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We establish a Galois connection between sub-monads of an augmented monad and sub-functors of the forgetful functor from its Eilenberg-Moore category. This connection is given in terms of invariants and stabilizers defined through universal…

Category Theory · Mathematics 2021-06-09 Johan Felipe García Vargas

We prove that algebraic stacks satisfy 2-descent for fppf coverings. We generalize Galois descent for schemes to stacks, by considering the case where the fppf covering is a finite Galois covering, and reformulating 2-descent data in terms…

Algebraic Geometry · Mathematics 2026-01-09 Olivier de Gaay Fortman

This article is on the inverse Galois problem in Galois theory of linear iterative differential equations in positive characteristic. We show that it has an affirmative answer for reduced algebraic group schemes over any iterative…

Commutative Algebra · Mathematics 2021-02-09 Andreas Maurischat

Given a group $G$, we define suitable 2-categorical structures on the class of all small categories with $G$-actions and on the class of all small $G$-graded categories, and prove that 2-categorical extensions of the orbit category…

Category Theory · Mathematics 2015-11-02 Hideto Asashiba

We prove that the category of ``vector bundles on the absolute Fargues--Fontaine curve'' (more precisely the category of sections over some discrete algebraically closed field of the $v$-stack $\mathrm{Bun}_\mathrm{FF}$ of vector bundles on…

Number Theory · Mathematics 2022-12-23 Johannes Anschütz

This paper establishes a purely syntactic representation for the category of algebraic L-domains with Scott-continuous functions as morphisms. The central tool used here is the notion of logical states, which builds a bridge between…

Logic in Computer Science · Computer Science 2020-07-10 Longchun Wang , Qingguo Li

We classify the finite groups whose non-linear irreducible characters that are not conjugate under the natural Galois action have distinct degrees, therefore extending the results in Berkovich et al. [Proc. Amer. Math. Soc. {\bf 115}…

Group Theory · Mathematics 2016-03-11 Silvio Dolfi , Manoj K. Yadav

For a finite Galois extension of fields L/k with Galois group G, we study a functor from the G-equivariant stable homotopy category to the stable motivic homotopy category over k induced by the classical Galois correspondence. We show that…

Algebraic Topology · Mathematics 2015-09-25 J. Heller , K. Ormsby

We establish the faithfulness of a geometric action of the absolute Galois group of the rationals that can be defined on the discriminantal variety associated to a finite complex reflection group, and review some possible connections with…

Group Theory · Mathematics 2012-02-28 Ivan Marin

This paper extends Hopf-Galois theory to infinite field extensions and provides a natural definition of subextensions. For separable (possibly infinite) Hopf-Galois extensions, it provides a Galois correspondence. This correspondence also…

Number Theory · Mathematics 2024-04-11 Hoan-Phung Bui , Joost Vercruysse , Gabor Wiese

We define a linear structure on Grothendieck's arithmetic fundamental group $\pi_1(X, x)$ of a scheme $X$ defined over a field $k$ of characteristic 0. It allows us to link the existence of sections of the Galois group ${\rm Gal}(\bar k/k)$…

Algebraic Geometry · Mathematics 2007-05-23 Hélène Esnault , Phùng Hô Hai

Past studies of the Brauer group of a scheme tells us the importance of the interrelationship among Brauer groups of its finite \'etale coverings. In this paper, we consider these groups simultaneously, and construct an integrated object…

Category Theory · Mathematics 2008-11-18 Hiroyuki Nakaoka

It has recently been proved that the category of N-manifolds of degree $n$, that is, $\mathbb N$-graded supermanifolds of degree $n$ for which the parity agrees with the gradation, is equivalent to the category of purely even $n$-tuple…

Differential Geometry · Mathematics 2026-02-18 Katarzyna Grabowska , Janusz Grabowski , Mikołaj Rotkiewicz

In this ongoing work, we extend to a class of well-behaved pre-special hyperfields the work of J. Min\'a\v c and Spira (\cite{minac1996witt}) that describes a (pro-2)-group of a field extension that encodes the quadratic form theory of a…

Commutative Algebra · Mathematics 2024-04-08 Kaique Matias de Andrade Roberto , Hugo Luiz Mariano

The main theorem of Galois theory states that there are no finite group-subgroup pairs with the same invariants. On the other hand, if we consider complex linear reductive groups instead of finite groups, the analogous statement is no…

Representation Theory · Mathematics 2007-05-23 S. Solomon

We present a simple proof of the fundamental theorem of Galois theory, which establishes a correspondence between the intermediate fields of a finite Galois extension and the subgroups of its Galois group. The proof is based on the…

Number Theory · Mathematics 2026-04-02 Martin Brandenburg

We prove that the Galois groupoid of the category of $G$-spectra for a finite group $G$ is algebraic, i.e. equivalent to the \'etale fundamental groupoid of the Burnside ring of $G$. We implement an algorithm that computes the latter from…

Algebraic Topology · Mathematics 2026-05-13 Niko Naumann , Luca Pol , Maxime Ramzi

We prove analogs of faithfully flat descent and Galois descent for categories of modules over $E_{\infty}$-ring spectra using the $\infty$-categorical Barr-Beck theorem proved by Lurie. In particular, faithful $G$-Galois extensions are…

Algebraic Topology · Mathematics 2015-09-15 Romie Banerjee

Let $S$ be a Dedekind scheme, $X$ a connected $S$-scheme locally of finite type and $x\in X(S)$ a section. The aim of the present paper is to establish the existence of the fundamental group scheme of $X$, when $X$ has reduced fibers or…

Algebraic Geometry · Mathematics 2024-04-10 Marco Antei , Michel Emsalem , Carlo Gasbarri

The Deligne groupoid is a functor from nilpotent differential graded Lie algebras concentrated in positive degrees to groupoids; in the special case of Lie algebras over a field of characteristic zero, it gives the associated simply…

Algebraic Topology · Mathematics 2018-01-16 Ezra Getzler