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We develop a homotopical variant of the classic notion of an algebraic theory as a tool for producing deformations of homotopy theories. From this, we extract a framework for constructing and reasoning with obstruction theories and spectral…

Algebraic Topology · Mathematics 2025-08-13 William Balderrama

It is proved that, in certain subgroups of direct products of countable groups, the property of being an unconditionally closed set coincides with that of being an algebraic set. In particular, these properties coincide in all Abelian…

Group Theory · Mathematics 2007-05-23 Ol'ga V. Sipacheva

In this paper we define a new algebraic object: the disguised-groups. We show the main properties of the disguised-groups and, as a consequence, we will see that disguised-groups coincide with regular semigroups. We prove many of the…

Group Theory · Mathematics 2020-06-08 Eduardo Blanco-Gómez

In this paper, we describe the possible disconnected complex reductive algebraic groups $E$ with component group $\Gamma = E/E_0$. We show that there is a natural bijection between such groups $E$ and algebraic extensions of $\Gamma$ by…

Representation Theory · Mathematics 2024-07-09 Marisa Gaetz , David Vogan

In the paper we describe the subcategory of the category of Z-graded Lie algebras which is equivalent to the category of Jordan pairs via a functorial modification of the TKK construction. For instance, we prove that a Z-graded Lie algebra…

Rings and Algebras · Mathematics 2011-06-14 Deanna M. Caveny , Oleg N. Smirnov

The Donald--Flanigan problem for a finite group H and coefficient ring k asks for a deformation of the group algebra kH to a separable algebra. It is solved here for dihedral groups and for the classical Weyl groups (whose rational group…

Quantum Algebra · Mathematics 2007-05-23 Murray Gerstenhaber , Anthony Giaquinto , Mary E. Schaps

We introduce the notion of difference equation defined on a structured set. The symmetry group of the structure determines the set of difference operators. All main notions in the theory of difference equations are introduced as invariants…

q-alg · Mathematics 2019-08-17 Per K. Jakobsen , Valentin V. Lychagin

In this paper, we propose an abstract definition of dependent type theories as essentially algebraic theories. One of the main advantages of this definition is its composability: simple theories can be combined into more complex ones, and…

Logic · Mathematics 2017-03-28 Valery Isaev

Difference families are traditionally built using groups as their basis. This paper looks at what sort of generalised difference family constructions could be made, using the standard basis of translation and difference. The main result is…

Combinatorics · Mathematics 2007-05-23 Tim Boykett

Every semigroup containing an ideal subgroup is called a homogroup, and it is a grouplike if and only if it has only one central idempotent. On the other hand, a class of algebraic structures covering group-$e$-semigroups…

Group Theory · Mathematics 2024-10-02 M. H. Hooshmand

The main aim of this paper is to classify the distinct multiplicative Lie algebra structures (up to isomorphism) on a given group. We also see that for a given group $G$, every homomorphism from the non-abelian exterior square $G \wedge G$…

Group Theory · Mathematics 2019-12-13 Mani Shankar Pandey , Sumit Kumar Upadhyay

In this paper, we will show that nonabelian simple classical groups of Lie type are uniquely determined by the structure of their complex group algebras.

Group Theory · Mathematics 2012-02-23 Hung P. Tong-Viet

Passing from arithmetic schemes to algebraic schemes, in a similar manner we will have the computation of the \'etale fundamental group of an algebraic scheme and then will define and discuss the qc fundamental group of an algebraic scheme…

Algebraic Geometry · Mathematics 2009-12-21 Feng-Wen An

A closed subgroup of a semisimple algebraic group is called irreducible if it lies in no proper parabolic subgroup. In this paper we classify all irreducible subgroups of exceptional algebraic groups $G$ which are connected, closed and…

Group Theory · Mathematics 2022-09-22 Adam Thomas

The Donald-Flanigan conjecture asserts that for any finite group and for any field, the corresponding group algebra can be deformed to a separable algebra. The minimal unsolved instance, namely the quaternion group over a field of…

Rings and Algebras · Mathematics 2007-05-23 Nurit Barnea , Yuval Ginosar

Let $G$ be a finite group and let $\textrm{cd}(G)$ be the set of all complex irreducible character degrees of $G.$ In this paper, we show that if $\textrm{cd}(G)=\textrm{cd}(H),$ where $H$ is a finite simple exceptional group of Lie type,…

Group Theory · Mathematics 2024-10-29 Hung P. Tong-Viet

In this paper, we construct a comparison map from the topological fundamental group to the pro-\'etale fundamental group for a complex variety.

Algebraic Geometry · Mathematics 2023-08-17 Jiu-Kang Yu , Lei Zhang

Regular algebraic $K$-theory for groups is a homology theory for discrete groups closely connected (but different from) group homology. It also gives a version of algebraic $K$-theory for rings by the simple functorial mapping assigning to…

K-Theory and Homology · Mathematics 2024-10-02 Ulrich Haag

When considering the unit group of $\mathcal{O}_F G$ ($\mathcal{O}_F$ the ring of integers of an abelian number field $F$ and a finite group $G$) certain components in the Wedderburn decomposition of $FG$ cause problems for known generic…

Representation Theory · Mathematics 2016-06-07 Andreas Bächle , Mauricio Caicedo , Inneke Van Gelder

We consider the natural Lie algebra structure on the (associative) group algebra of a finite group $G$, and show that the Lie subalgebras associated to natural involutive antiautomorphisms of this group algebra are reductive ones. We give a…

Representation Theory · Mathematics 2008-09-02 Ivan Marin