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We develop a theory of separable ring extensions and separable functors for nonunital rings in the setting of firm modules. We prove nonunital analogues of classical results on functorial separability and semisimplicity, and apply these…

Rings and Algebras · Mathematics 2026-05-26 Patrik Lundström

In this paper, we study arbitrary models of the first-order theory of a ring $A$ where the additive group $A$ is a finitely generated abelian group. Following an earlier paper by this author, Alexei G. Myasnikov and Francis Oger, we call…

Logic · Mathematics 2026-03-31 Mahmood Sohrabi

For commutative rings, we introduce the notion of a {\em universal grading}, which can be viewed as the "largest possible grading". While not every commutative ring (or order) has a universal grading, we prove that every {\em reduced order}…

Commutative Algebra · Mathematics 2018-04-18 H. W. Lenstra, , A. Silverberg

In algebraic geometry over a variety of universal algebras $\Theta $, the group $Aut(\Theta ^{0})$ of automorphisms of the category $\Theta ^{0}$ of finitely generated free algebras of $\Theta $ is of great importance. In this paper,…

Rings and Algebras · Mathematics 2007-05-23 Yefim Katsov , Ruvim Lipyanski , Boris Plotkin

In this paper, we prove that if Cohen-Macaulay local/graded rings $R_1$, $R_2$ and $R$ satisfy certain conditions regarding multiplicity and Cohen-Macaulay type, then almost Gorenstein property of $R$ implies Gorenstein properties for all…

Commutative Algebra · Mathematics 2023-12-29 Koji Matsushita , Sora Miyashita

This paper is lead by the question whether there is a nice structure theory of finitely generated modules over the Iwasawa algebra, i.e. the completed group algebra, R of a p-adic analytic group G. For G without any p-torsion element we…

Number Theory · Mathematics 2007-05-23 Otmar Venjakob

We classify subalgebras of a ring of differential operators which are big in the sense that the extension of associated graded rings is finite. We show that these subalgebras correspond, up to automorphisms, to uniformly ramified finite…

Rings and Algebras · Mathematics 2007-05-23 Friedrich Knop

In this article we generalize a classical result by Passman on primeness of unital strongly group graded rings to the class of nearly epsilon-strongly group graded rings which are not necessarily unital. Using this result, we obtain (i) a…

Rings and Algebras · Mathematics 2025-12-24 Daniel Lännström , Patrik Lundström , Johan Öinert , Stefan Wagner

Given a graded ample Hausdorff groupoid, we realise its graded Steinberg algebra as a partial skew inverse semigroup ring. We use this to show that for a partial action of a discrete group on a locally compact Hausdorff topological space,…

Rings and Algebras · Mathematics 2017-08-18 Roozbeh Hazrat , Huanhuan Li

Torsion theories are a pinnacle in the theory of abelian categories. They are a generalization of torsion abelian groups and in this generalization one of the most studied is that whose torsionfree class consists of nonsingular modules. To…

In a recent paper of Alahmadi, Alkan and Lopez-Permouth, a ring R is defined to have no (simple) middle class if the injectivity domain of any (simple) R-module is the smallest or largest possible. Er, Lopez-Permouth and Sokmez use this…

Rings and Algebras · Mathematics 2012-11-27 Pinar Aydogdu , Bulent Sarac

As an extension of previous ungraded work, we define a graded $p$-polar ring to be an analog of a graded commutative ring where multiplication is only allowed on $p$-tuples (instead of pairs) of elements of equal degree. We show that the…

Algebraic Topology · Mathematics 2025-05-06 Tilman Bauer

We study modules for the divided power algebra $D$ in a single variable over a commutative noetherian ring $k$. Our first result states that $D$ is a coherent ring. In fact, we show that there is a theory of Gr\"obner bases for finitely…

Commutative Algebra · Mathematics 2018-02-20 Rohit Nagpal , Andrew Snowden

We propose two definitions of configuration Lie groupoids and in both the cases we prove a Fadell-Neuwirth type fibration theorem for a class of Lie groupoids. We show that this is the best possible extension, in the sense that, for the…

Geometric Topology · Mathematics 2025-08-08 S K Roushon

We study the arithmetic of seminormal $v$-noetherian weakly Krull monoids with nontrivial conductor which have finite class group and prime divisors in all classes. These monoids include seminormal orders in holomorphy rings in global…

Commutative Algebra · Mathematics 2015-08-05 Alfred Geroldinger , Florian Kainrath , Andreas Reinhart

We construct a number of different examples of non-Noetherian graded rings that are injective as modules over themselves (or have some related but weaker properties). We discuss how these are related to the theory of triangulated…

Commutative Algebra · Mathematics 2016-01-20 Leigh Shepperson , Neil Strickland

This paper is a major step in the classification of endotrivial modules over p-groups. Let G be a finite p-group and k be a field of characteristic p. A kG-module M is an endo-trivial module if {\End_k(M)\cong k\oplus F} as kG-modules,…

Group Theory · Mathematics 2007-06-28 Jon F. Carlson , Jacques Thevenaz

Let $\Gamma$ be a finitely generated torsion-free group. We show that the statement of $\Gamma$ being virtually abelian is equivalent to the statement that the $*$-regular closure of the group ring $\mathbb{C}[\Gamma]$ in the algebra of…

Group Theory · Mathematics 2023-03-07 Joan Claramunt , Lukasz Grabowski

We prove that the group of automorphisms of the category of free modules over Noterian rings is semi-inner and present also a short proof of a similar result for the variery of Lie algebras.

Rings and Algebras · Mathematics 2007-05-23 R. Lipyanski , B. Plotkin

Let $R$ be a commutative ring and $\Gamma$ be an infinite discrete group. The algebraic $K$-theory of the group ring $R[\Gamma]$ is an important object of computation in geometric topology and number theory. When the group ring is…

K-Theory and Homology · Mathematics 2016-07-04 Gunnar Carlsson , Boris Goldfarb