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We show that the abstract commensurator of an S-arithmetic subgroup of a solvable algebraic group over Q is isomorphic to the Q-points of an algebraic group, and compare this with examples of nonlinear abstract commensurators of…

Group Theory · Mathematics 2016-06-22 Daniel Studenmund

We show the vanishing of the second homotopy group of the \'etale homotopy type of a smooth connected algebraic group over a separably closed field, completed away from the characteristic. This is an algebraic analogue of a classical…

Algebraic Geometry · Mathematics 2022-06-23 Cyril Demarche , Tamás Szamuely

We reduce the isomorphism problem for undirected graphs without loops to the isomorphism problems for a class of finite dimensional $2$-step nilpotent Lie algebras over a field and for a class of finite $p$-groups. We show that the…

Group Theory · Mathematics 2020-08-03 Ruvim Lipyanski , Natalia Vanetik

For a geometrically rational surface X over an arbitrary field of characteristic different from 2 and 3 that contains all roots of 1, we show that either X is birational to a product of a projective line and a conic, or the group of…

Algebraic Geometry · Mathematics 2020-08-18 Constantin Shramov , Vadim Vologodsky

The first author has recently shown that semisimple algebraic groups are classified up to motivic equivalence by the local versions of the classical Tits indexes over field extensions, known as Tits p-indexes. We provide in this article the…

Algebraic Geometry · Mathematics 2017-09-26 Charles De Clercq , Skip Garibaldi

We propose a general quantum Hamiltonian formalism of a renormalization group (RG) flow with an emphasis on generalized symmetry by interpreting the elementary relationship between homomorphism, quotient ring, and projection. In our…

High Energy Physics - Theory · Physics 2026-04-09 Yoshiki Fukusumi , Yuma Furuta

The paper discuss the limit point concept of a subset in a group via ideal of the power set ring. This idea along with anti-ideal give the topological structure in a group. Homomorphic images of both ideal and anti-ideal are played the…

Rings and Algebras · Mathematics 2026-05-04 Monoj Kumar Das , Shyamapada Modak

This paper provides an extensive study of the homotopy theory of types of algebras with units, like unital associative algebras or unital commutative algebras for instance. To this purpose, we endow the Koszul dual category of curved…

Algebraic Topology · Mathematics 2019-05-29 Brice Le Grignou

In this paper we describe orbits of automorphism group on a horospherical variety in terms of degrees of homogeneous with respect to natural grading locally nilpotent derivations. In case of (may be non-normal) toric varieties a description…

Algebraic Geometry · Mathematics 2021-05-14 Viktoriia Borovik , Sergey Gaifullin , Anton Shafarevich

In this paper we develop an axiomatic setup for algorithmic homological algebra of Abelian categories. This is done by exhibiting all existential quantifiers entering the definition of an Abelian category, which for the sake of…

Commutative Algebra · Mathematics 2017-10-27 Mohamed Barakat , Markus Lange-Hegermann

We consider a problem whether a given Lie group can be realized as the group of all biholomorphic automorphisms of a bounded domain in the affine complex space. In an earlier paper of 1990, we proved the result for connected linear Lie…

Complex Variables · Mathematics 2025-04-07 George Shabat , Alexander Tumanov

We build on our construction of Hopf algebroids from noncommutative calculi under the further assumption of surjectivity for the calculus. We also introduce the notions of Hopf ideals and isotopy quotients for arbitrary Hopf algebroids.…

Quantum Algebra · Mathematics 2021-08-18 Aryan Ghobadi

In this paper, we revisit the problem of classifying real algebraic and semialgebraic sets by their topological types, focusing on establishing the effectiveness of bounds rather than deriving new quantitative estimates. Building on Hardt's…

Algebraic Geometry · Mathematics 2024-12-24 Kartoue Mady Demdah , Ibrahim Nonkane

We introduce the group-compact coarse structure on a Hausdorff topological group in the context of coarse structures on an abstract group which are compatible with the group operations. We develop asymptotic dimension theory for the…

Geometric Topology · Mathematics 2012-01-24 Andrew Nicas , David Rosenthal

We prove that a homotopy cofinal functor between small categories induces a weak equivalence between homotopy colimits of pointed simplicial sets. This is used to prove that the non-Abelian homology of a group diagram is isomorphic to the…

Algebraic Topology · Mathematics 2024-03-27 Ahmet A. Husainov

In this paper, we study rationality properties of reductive group actions which are defined over an arbitrary field of characteristic zero. Thereby, we unify Luna's theory of spherical systems and Borel-Tits' theory of reductive groups. In…

Representation Theory · Mathematics 2024-09-25 Friedrich Knop , Bernhard Krötz

The article gives the second part of the treatise on Regular Algebraic $K$-theory (Sections V & VI) of the author. Regular algebraic $K$-theory for groups is a homology theory for discrete groups closely connected to (but different from)…

K-Theory and Homology · Mathematics 2024-10-11 Ulrich Haag

In this paper we begin the systematic study of group equations with abelian predicates in the main classes of groups where solving equations is possible. We extend the line of work on word equations with length constraints, and more…

Group Theory · Mathematics 2022-05-02 Laura Ciobanu , Albert Garreta

In this article, we establish results concerning the cohomology of Zariski dense subgroups of solvable linear algebraic groups. We show that for an irreducible solvable $\mathbb{Q}$-defined linear algebraic group $\mathbf{G}$, there exists…

Group Theory · Mathematics 2026-04-14 Milana Golich , Antonio López Neumann , Mark Pengitore

A monomial algebra B is defined as a quotient of a polynomial ring by a monomial ideal, which is an ideal generated by a finite set of monomials. In this paper, we determine the automorphism group of a monomial algebra B, under the…

Algebraic Geometry · Mathematics 2026-04-28 Roberto Díaz , Alvaro Liendo , Gonzalo Manzano-Flores , Andriy Regeta