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We introduce the notion of amenability for affine algebras. We characterize amenability by Folner-sequences, paradoxicality and the existence of finitely invariant dimension-measures. Then we extend the results of Rowen on ranks, from…

Rings and Algebras · Mathematics 2007-05-23 Gabor Elek

We continue the investigation of notions of approximate amenability that were introduced in work of the second and third authors. It is shown that every boundedly approximately contractible Banach algebra has a bounded approximate identity.…

Functional Analysis · Mathematics 2009-03-26 Y. Choi , F. Ghahramani , Y. Zhang

A cycle is algebraically trivial if it can be exhibited as the difference of two fibers in a family of cycles parameterized by a smooth scheme. Over an algebraically closed field, it is a result of Weil that it suffices to consider families…

Algebraic Geometry · Mathematics 2020-02-27 Jeff Achter , Sebastian Casalaina-Martin , Charles Vial

We introduce the notion of bounded quasi-inversion closed semiprime f-algebras and we prove that, if A is such an algebra, then any intermediate algebra in A is an order ideal of A. This extends a recent result by Dominguez who has dealt…

Functional Analysis · Mathematics 2025-02-04 Karim Boulabiar

Possible irreducible holonomy algebras $\g\subset\osp(p,q|2m)$ of Riemannian supermanifolds under the assumption that $\g$ is a direct sum of simple Lie superalgebras of classical type and possibly of a one-dimensional center are…

Differential Geometry · Mathematics 2018-08-21 Anton S. Galaev

We initiate a systematic study of lattices of thick subcategories for arbitrary essentially small triangulated categories. To this end we give several examples illustrating the various properties these lattices may, or may not, have and…

Category Theory · Mathematics 2023-04-25 Sira Gratz , Greg Stevenson

The cluster category is a triangulated category introduced for its combinatorial similarities with cluster algebras. We prove that a cluster algebra A of finite type can be realized as a Hall algebra, called the exceptional Hall algebra, of…

Representation Theory · Mathematics 2007-05-23 Philippe Caldero , Bernhard Keller

The proximinality of certain subspaces of spaces of bounded affine functions is proved. The results presented here are some linear versions of an old result due to Mazur. For the proofs we use some sandwich theorems of Fenchel's duality…

Functional Analysis · Mathematics 2019-07-24 Maysam Maysami Sadr

Conformal algebras, recently introduced by Kac, encode an axiomatic description of the singular part of the operator product expansion in conformal field theory. The objective of this paper is to develop the theory of ``multi-dimensional''…

Quantum Algebra · Mathematics 2007-05-23 Bojko Bakalov , Alessandro D'Andrea , Victor G. Kac

We study the representation theory of the infinite type A Hecke algebra over a non-archimedean field in the case where the parameter is a pseudo-uniformizer. Specifically, we consider a family of representations, called almost-symmetric,…

Representation Theory · Mathematics 2026-03-25 Milo Bechtloff Weising

We characterize vertex algebras (in a suitable sense) as algebras over a certain graded co-operad. We also discuss some examples and categorical implications of this characterization.

Rings and Algebras · Mathematics 2010-06-02 Ruthi Hortsch , Igor Kriz , Ales Pultr

Quasi-Boolean algebras were introduced as the generalization of Boolean algebras in the setting of quantum computation logic. In this paper, we investigate the completeness and congruences of quasi-Boolean algebras. First, we discuss the…

Logic · Mathematics 2025-10-28 Xiaohao Liu , Heyan Wang , Wenjuan Chen

We introduce a class of Banach algebras of generalized matrices and study the existence of approximate units, ideal structure, and derivations of them.

Functional Analysis · Mathematics 2016-05-16 Maysam Maysami Sadr

In the first half of this paper, we define axial algebras: nonassociative commutative algebras generated by axes, that is, semisimple idempotents---the prototypical example of which is Griess' algebra [C85] for the Monster group. When…

Rings and Algebras · Mathematics 2015-06-26 J. I. Hall , F. Rehren , S. Shpectorov

We study topological aspects of the category of abstract Cuntz semigroups, termed Cu. We provide a suitable setting in which we are able to uniformly control how to approach an element of a Cu-semigroup by a rapidly increasing sequence.…

Operator Algebras · Mathematics 2022-06-17 Laurent Cantier

In this article we describe indecomposable objects of the derived categories of a branch class of associative algebras. To this class belong such known classes of algebras as gentle algebras, skew-gentle algebras and certain degenerations…

Representation Theory · Mathematics 2016-09-07 Igor Burban , Yuriy Drozd

The class of finitely presented algebras over a field $K$ with a set of generators $a_{1},..., a_{n}$ and defined by homogeneous relations of the form $a_{1}a_{2}... a_{n} =a_{\sigma (a)} a_{\sigma (2)} ... a_{\sigma (n)}$, where $\sigma$…

Rings and Algebras · Mathematics 2008-10-03 F. Cedo , E. Jespers , J. Okninksi

We study thick subcategories of derived categories of gentle algebras. Any thick subcategory of a derived category of a gentle algebra is generated by a set of string objects or a set of band objects. We show the thick subcategories…

Representation Theory · Mathematics 2025-02-18 Callum Page

In this paper we build an abstract description of vertex algebras from their basic axioms. Starting with Borcherds' notion of a vertex group, we naturally construct a family of multilinear singular maps parameterised by trees. These…

Quantum Algebra · Mathematics 2007-05-23 Craig T. Snydal

For a large class of finite W algebras, the defining relations of a Yangian are proved to be satisfied. Therefore such finite W algebras appear as realisations of Yangians. This result is useful to determine properties of such W algebra…

High Energy Physics - Theory · Physics 2007-05-23 E. Ragoucy , P. Sorba