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We show that countable increasing unions preserve a large family of well-studied covering properties, which are not necessarily sigma-additive. Using this, together with infinite-combinatorial methods and simple forcing theoretic methods,…

General Topology · Mathematics 2018-04-06 Tal Orenshtein , Boaz Tsaban

Given a contraction of a variety X to a base Y, we enhance the locus in Y over which the contraction is not an isomorphism with a certain sheaf of noncommutative rings D, under mild assumptions which hold in the case of (1) crepant partial…

Algebraic Geometry · Mathematics 2018-11-28 Will Donovan , Michael Wemyss

We establish a structure theorem for minimizing sequences for the isoperimetric problem on noncompact $\mathsf{RCD}(K,N)$ spaces $(X,\mathsf{d},\mathcal{H}^N)$. Under the sole (necessary) assumption that the measure of unit balls is…

Differential Geometry · Mathematics 2022-08-30 Gioacchino Antonelli , Stefano Nardulli , Marco Pozzetta

Let R=K[M] be a normal affine monoid algbera over a field K.Up to isomorphism the conic ideals are exactly the direct summands ofthe extension R^{1/n} of R. We show that the classes of the conic divisorial ideals can be identified with the…

Commutative Algebra · Mathematics 2007-05-23 Winfried Bruns

We define the notion of an indexed profunctor over a 2-category, and use it to develop an abstract theory of limits. The theory subsumes (conical) limits, weighted limits, ends and Kan extensions. Results include an abstract version of the…

Category Theory · Mathematics 2023-02-14 Sori Lee

The notes start with an elementary introduction to a few important analytic techniques of algebraic geometry: closed positive currents, $L^2$ estimates for the $\dbar$-operator on positive vector bundles, Nadel's vanishing theorem for…

alg-geom · Mathematics 2015-06-30 Jean-Pierre Demailly

The purpose of this article is to further explore how the structure of the affine group can be used to deduce new incidence theorems, and to explore sum-product type applications of these incidence bounds, building on the recent work of…

Combinatorics · Mathematics 2019-05-10 Oliver Roche-Newton , Audie Warren

The aim of this paper is to study co-prolongations of central extensions. We construct the obstruction theory for co-prolongations and classify the equivalence classes of these by kernels of a homomorphisms between 2-dimensional cohomology…

Group Theory · Mathematics 2013-09-13 Nguyen Tien Quang , Doan Trong Tuyen , Nguyen Thi Thu Thuy

We present here some conjectures on the diagonalizability of uniform principal bundles on rational homogeneous spaces, that are natural extensions of classical theorems on uniform vector bundles on the projective space, and study the…

Algebraic Geometry · Mathematics 2025-04-01 Roberto Muñoz , Gianluca Occhetta , Luis E. Solá Conde

Paley-Wiener type theorems describe the image of a given space of functions, often compactly supported functions, under an integral transform, usually a Fourier transform on a group or homogeneous space. Several authors have studied…

Representation Theory · Mathematics 2015-12-01 Vivian M. Ho , Gestur Olafsson

Extensions of a set partition obtained by imposing bounds on the size of the parts and the coloring of some of the elements are examined. Combinatorial properties and the generating functions of some counting sequences associated with these…

Combinatorics · Mathematics 2021-03-09 István Mezo , Victor H. Moll , José L. Ramírez , Diego Villamizar

The first goal of the article is to solve several fundamental problems in the theory of holomorphic bundles over non-algebraic manifolds: For instance we prove that stability and semi-stability are Zariski open properties in families when…

Differential Geometry · Mathematics 2007-05-23 Andrei Teleman

We prove that there exist infinite families of regular bipartite Ramanujan graphs of every degree bigger than 2. We do this by proving a variant of a conjecture of Bilu and Linial about the existence of good 2-lifts of every graph. We also…

Combinatorics · Mathematics 2014-03-04 Adam Marcus , Daniel A. Spielman , Nikhil Srivastava

Incidence theorems concern configurations of points, lines, and, more generally, higher-dimensional subspaces in projective space. Broadly speaking, such theorems fall into two classes: those that hold over an arbitrary division ring, such…

Combinatorics · Mathematics 2026-03-24 Anton Izosimov

A partial group is a generalization of the concept of group recently introduced by A. Chermak. By considering partial groups as simplicial sets, we propose an extension theory for partial groups using the concept of (simplicial) fibre…

Algebraic Topology · Mathematics 2015-09-04 Alex Gonzalez

We analyze model-theoretic connected components in extensions of a given group by abelian groups which are defined by means of 2-cocycles with finite image. We characterize, in terms of these 2-cocycles, when the smallest type-definable…

Logic · Mathematics 2013-12-16 Jakub Gismatullin , Krzysztof Krupinski

We prove a common generalization to several mass partition results using hyperplane arrangements to split $\mathbb{R}^d$ into two sets. Our main result implies the ham-sandwich theorem, the necklace splitting theorem for two thieves, a…

Combinatorics · Mathematics 2024-04-30 Alfredo Hubard , Pablo Soberón

In this expositional paper, we discuss commutative algebra -- a study inspired by the properties of integers, rational numbers, and real numbers. In particular, we investigate rings and ideals, and their various properties. After, we…

Algebraic Geometry · Mathematics 2021-10-19 Marc Maliar

G. Conner and K. Eda (Topology and its Applications, 146, (2005), 317-328.) introduced a new construction of spaces from groups. They remarked that the construction is not categorical. In this paper, based on the work of Conner and Eda, we…

Algebraic Topology · Mathematics 2011-03-10 Hanieh Mirebrahimi , Behrooz Mashayekhy

Topologies can be expanded with the help of ideals, using the local function, an operator resembling the closure of a set. The aim of this paper is to define the ideals which enable us to create this topology $\tau^{*}$ on $X$…

General Topology · Mathematics 2023-12-07 Anika Njamcul , Aleksandar Pavlović
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