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We provide necessary and sufficient conditions for when an algebraic stack admits a good moduli space and prove a semistable reduction theorem for points of algebraic stacks equipped with a $\Theta$-stratification. These results provide a…

Algebraic Geometry · Mathematics 2024-02-26 Jarod Alper , Daniel Halpern-Leistner , Jochen Heinloth

We describe an abelian category $\mathbf{ab}(M)$ in which the solution sets of finitely many linear equations over an arbitrary ring $R$ with values in an arbitrary left $R$-module $M$ reside as objects. Such solution sets are also called…

Category Theory · Mathematics 2023-10-03 Sebastian Posur

Let F be a global field, and let S be a finite set of places of F containing all archimedean places. Consider the product X of the symmetric spaces and Bruhat-Tits buildings for PGL_d of the completions of F at archimedean and…

Number Theory · Mathematics 2016-12-12 Takako Fukaya , Kazuya Kato , Romyar Sharifi

In this article we describe the $G\times G$-equivariant $K$-ring of $X$, where $X$ is a regular compactification of a connected complex reductive algebraic group $G$. Furthermore, in the case when $G$ is a semisimple group of adjoint type,…

Algebraic Geometry · Mathematics 2007-06-12 V. Uma

Let $K$ be an algebraically closed field of arbitrary characteristic and let $X$ be an irreducible projective variety over $K$. Let $G\subseteq\text{Bir}(X)$ be a bounded-degree subgroup. We prove that there exists an irreducible projective…

Algebraic Geometry · Mathematics 2024-03-13 She Yang

Let X be a building of arbitrary type. A compactification $C_r(X)$ of the set Res(X) of spherical residues of X is introduced. We prove that it coincides with the horofunction compactification of Res(X) endowed with a natural combinatorial…

Group Theory · Mathematics 2009-01-28 Pierre-Emmanuel Caprace , Jean Lecureux

We establish formulas for computation of the higher algebraic $K$-groups of the endomorphism rings of objects linked by a morphism in an additive category. Let ${\mathcal C}$ be an additive category, and let $Y\ra X$ be a covariant morphism…

K-Theory and Homology · Mathematics 2018-05-01 Hongxing Chen , Changchang Xi

In this paper, we study lower bounds on the K-theory of the maximal $C^*$-algebra of a discrete group based on the amount of torsion it contains. We call this the finite part of the operator K-theory and give a lower bound that is valid for…

Operator Algebras · Mathematics 2013-08-23 Shmuel Weinberger , Guoliang Yu

We study equivariant projective compactifications of reductive groups obtained by closing the image of a group in the space of operators of a projective representation. We describe the structure and the mutual position of their orbits under…

Algebraic Geometry · Mathematics 2015-06-26 Dmitri A. Timashev

A 1-parameter variation of Hodge structures corresponds to a holomorphic, horizontal, locally liftable map into a classifying space of Hodge structures. In this paper it is shown that such a map has a limit in the reductive Borel-Serre…

Algebraic Geometry · Mathematics 2014-03-21 John Scherk

Let G be a semisimple linear algebraic group defined over rational numbers, K be a maximal compact subgroup of its real points and {\Gamma} be an arithmetic lattice. One can associate a probability measure {\mu}(H) on {\Gamma}\G for each…

Dynamical Systems · Mathematics 2021-01-15 Runlin Zhang

The structure space S(M) of a closed topological m-manifold M classifies bundles whose fibers are closed m-manifolds equipped with a homotopy equivalence to M. We construct a highly connected map from S(M) to a concoction of algebraic…

Algebraic Topology · Mathematics 2013-08-20 Michael S. Weiss , E. Bruce Williams

We initiate the effective metric structure theory of Keisler randomizations. We show that a classical countable structure $\mathcal{M}$ has a decidable presentation if and only if its Borel randomization $\mathcal{M}^{[0,1)}$ has a…

Logic · Mathematics 2025-06-09 Nicolás Cuervo Ovalle , Isaac Goldbring

In this paper we apply a recently proposed algebraic theory of integration to projective group algebras. These structures have received some attention in connection with the compactification of the $M$ theory on noncommutative tori. This…

Mathematical Physics · Physics 2009-10-31 R. Casalbuoni

We provide a universal characterization of the construction taking a scheme $X$ to its stable $\infty$-category $\text{Mot}(X)$ of noncommutative motives, patterned after the universal characterization of algebraic K-theory due to…

K-Theory and Homology · Mathematics 2024-08-21 Aaron Mazel-Gee , Reuben Stern

We generalize a recent result of Clausen: For a number field with integers O, we compute the K-theory of locally compact O-modules. For the rational integers this recovers Clausen's result as a special case. Our method of proof is quite…

K-Theory and Homology · Mathematics 2017-10-31 Oliver Braunling

We construct a compactification $M^{\mu ss}$ of the Uhlenbeck-Donaldson type for the moduli space of slope stable framed bundles. This is a kind of a moduli space of slope semistable framed sheaves. We show that there exists a projective…

Algebraic Geometry · Mathematics 2023-08-08 Ugo Bruzzo , Dimitri Markushevich , Alexander Tikhomirov

A definition of summability is put forward in the framework of general Carleman ultraholomorphic classes in sectors, so generalizing $k-$summability theory as developed by J.-P. Ramis. Departing from a strongly regular sequence of positive…

Complex Variables · Mathematics 2014-02-10 Alberto Lastra , Stephane Malek , Javier Sanz

A discrete countable group G is matricially stable if the finite dimensional approximate unitary representations of G are perturbable to genuine representations in the point-norm topology. For large classes of groups G, we show that…

Operator Algebras · Mathematics 2021-03-19 Marius Dadarlat

We view strict ring spectra as generalized rings. The study of their algebraic K-theory is motivated by its applications to the automorphism groups of compact manifolds. Partial calculations of algebraic K-theory for the sphere spectrum are…

Algebraic Topology · Mathematics 2022-06-22 John Rognes