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Let u be a local homomorphism of noetherian local rings forming part of a commutative square vf=gu. We give some conditions on the square which imply that u is formally smooth. This result encapsulates a variety of (apparently unrelated)…

Commutative Algebra · Mathematics 2019-06-19 Javier Majadas

Let $X$ be a locally Noetherian scheme with a closed subscheme $Z$. Let $\mathcal{X}$ be the completion of $X$ at $Z$, considered as a formal scheme. We show that a coherent sheaf on $X$ is equivalently given by a coherent sheaf on…

Algebraic Geometry · Mathematics 2023-12-18 Robin Louis

Let p=tp(a/A) be a stationary type in an arbitrary finite rank stable theory, and P an A-invariant family of partial types. The following property is introduced and characterised: whenever c is definable over (A,a) and a is not algebraic…

Logic · Mathematics 2013-12-19 Rahim Moosa , Anand Pillay

This work focuses on approximation and generation for the derived category of complexes with quasi-coherent cohomology on algebraic stacks. Our methods establish that approximation by compact objects descends along covers that are…

Algebraic Geometry · Mathematics 2025-05-01 Jack Hall , Alicia Lamarche , Pat Lank , Fei Peng

To a smooth and proper morphism $\mathcal{X}\to U$ with quasicompact semiseparated target we associate a sheaf in the \'etale topology, which takes an affine $U$-scheme $V$ to the set of $V$-linear semiorthogonal decompositions (of fixed…

Algebraic Geometry · Mathematics 2025-11-17 Pieter Belmans , Shinnosuke Okawa , Andrea T. Ricolfi

This thesis is an exposition of the author's contribution on effective descent morphisms in various categories of generalized categorical structures. It consists of: Chapter 1, where an elementary description of descent theory and the…

Category Theory · Mathematics 2025-02-14 Rui Prezado

We give sufficient conditions for the affinity of Etingof's sheaves of Cherednik algebras on projective space. To do this we introduce the notion of pull-back of modules under certain flat morphisms.

Representation Theory · Mathematics 2016-01-20 Gwyn Bellamy , Maurizio Martino

A uniform space is a topological space together with some additional structure which allows one to make sense of uniform properties such as completeness or uniform convergence. Motivated by previous work of J. Rivera-Letelier, we give a new…

Number Theory · Mathematics 2007-05-23 Matthew Baker

We develop in this article flattening techniques for coherent sheaves in the realm of Berkovich spaces; we are inspired by the general strategy that Raynaud and Gruson have used for dealing with the analogous problem in scheme theory. As an…

Algebraic Geometry · Mathematics 2021-07-01 Antoine Ducros

We show that the weakly \'etale morphisms, used to define the pro-\'etale site of a scheme, are characterized by a lifting property similar to the one which characterizes formally \'etale morphisms. In order to prove this, we prove a…

Algebraic Geometry · Mathematics 2022-02-15 Aise Johan de Jong , Noah Olander

We show that the inertia stack of a topological stack is again a topological stack. We further observe that the inertia stack of an orbispace is again an orbispace. We show how a U(1)-banded gerbe over an orbispace gives rise to a flat line…

K-Theory and Homology · Mathematics 2018-11-28 Ulrich Bunke , Markus Spitzweck , Thomas Schick

In spaces of nonpositive curvature the existence of isometrically embedded flat (hyper)planes is often granted by apparently weaker conditions on large scales. We show that some such results remain valid for metric spaces with non-unique…

Metric Geometry · Mathematics 2016-03-15 Dominic Descombes , Urs Lang

By a closure space we will mean a pair $(A,\mathcal{C})$, in which $A$ is a set and $\mathcal{C}$ a set of subsets of $A$ closed under arbitrary intersections. The purpose of this paper is to initiate a development of descent theory of…

Category Theory · Mathematics 2023-10-26 George Janelidze , Manuela Sobral

Through the subsequent discussion we consider a certain particular sort of (topological) algebras, which may substitute the `` structure sheaf algebras'' in many--in point of fact, in all--the situations of a geometrical character that…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Anastasios Mallios

This paper develops the basic theory of formal schemes over fields in the supersymmetric setting. We introduce the notion of a formal superscheme and investigate some of its fundamental properties. Particular emphasis is placed on the study…

Algebraic Geometry · Mathematics 2025-11-12 Felipe Saenz , Joel Torres del Valle

The ascent and descent of the Mittag-Leffler property were instrumental in proving Zariski locality of the notion of an (infinite dimensional) vector bundle by Raynaud and Gruson in \cite{RG}. More recently, relative Mittag-Leffler modules…

Algebraic Geometry · Mathematics 2025-04-25 Asmae Ben Yassine , Jan Trlifaj

We prove two flat descent statements for Artin n-stacks. We first show that an n-stack for the etale topology which is an Artin n-stack in the sense of HAGII, is also an n-stack for the fppf topology. Moreover, an n-stack for the fppf…

Algebraic Geometry · Mathematics 2010-01-07 B. Toen

Since their inception perfectoid spaces have catalyzed a revolution in p-adic geometry. We redevelop the foundations of perfectoid spaces from the point of view of Berkovich Spaces, where the underlying topological space of an affinoid…

Algebraic Geometry · Mathematics 2023-04-20 Attilio Castano

After introducing some motivations for this survey, we describe a formalism to parametrize a wide class of algebraic structures occurring naturally in various problems of topology, geometry and mathematical physics. This allows us to define…

Algebraic Topology · Mathematics 2016-12-16 Sinan Yalin

We investigate affine Berkovich spaces over maximally complete fields and prove that they may be approximated by simpler spaces when the only functions we need to evaluate are polynomials of bounded degree. We derive applications to…

Algebraic Geometry · Mathematics 2012-04-17 Jérôme Poineau