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In this paper, we characterize $\ell$-open and $\ell$-closed $C^*$-algebras and deduce that $\ell$-open $C^*$-algebras are $\ell$-closed, as conjectured by Blackadar. Moreover, we show that a commutative unital $C^*$-algebra is $\ell$-open…

Operator Algebras · Mathematics 2024-01-31 Dolapo Oyetunbi , Aaron Tikuisis

Over a field of characteristic zero, we prove that the Freiheitssatz holds for brace algebras, the word problem for the brace algebras with a single defining relation is decidable, two generated subalgebras of free brace algebras are free,…

Rings and Algebras · Mathematics 2018-10-02 Yu Li , Qiuhui Mo , Xiangui Zhao

Let k be an algebraically closed field of characteristic p> 0. For a basic classical Lie superalgebra, we show its restricted cohomology algebra is a finitely generated algebra. Thus the cohomological support theory can be established. As a…

K-Theory and Homology · Mathematics 2012-05-29 Gongxiang Liu

Simple Lie algebras of finite dimension over an algebraically closed field of characteristic 0 or $p> 3$ were recently classified. However, the problem over an algebraically closed field of characteristics 2 or 3 there exist only partial…

Rings and Algebras · Mathematics 2019-03-04 Carlos Rafael Payares Guevara , Jeovanny de Jesus Muentes Acevedo

We classify (possibly non commutative) algebras of low rank over a domain R. We first review results for algebras of rank 2 and for finite-dimensional division algebras over the real numbers. These results motivate us to consider which…

Rings and Algebras · Mathematics 2013-12-24 Alex S. E. Levin

A closed discrete subset $A\subset \mathbb{C}$ is called tame if $\mathbb{C}\setminus A$ is quasiconformally equivalent to $\mathbb{C}\setminus \mathbb{Z}$. By giving several criteria for $A$ to be tame, we shall show that…

Differential Geometry · Mathematics 2014-05-05 H. Fujino

Given a finite-dimensional noncommutative semisimple algebra $A$ with involution, we show that $A$ always has an RBA-basis. We look for an RBA-basis that has integral or rational structure constants, and ask if the RBA admits a positive…

Rings and Algebras · Mathematics 2016-08-03 Allen Herman , Mikhael Muzychuk , Bangteng Xu

We establish representation types (finite, tame or wild) of finite dimensional Munn algebras with semisimple bases. As an application, we establish representation types of finite 0-simple semigroups and their mutually annihilating unions.

Representation Theory · Mathematics 2022-08-22 Yuriy A. Drozd , Andriana I. Plakosh

This note presents a discussion of the algebraic and combinatorial aspects of the theory of pure O-sequences. Various instances where pure O-sequences appear are described. Several open problems that deserve further investigation are also…

Commutative Algebra · Mathematics 2013-02-20 Juan Migliore , Uwe Nagel , Fabrizio Zanello

This note was originated many years ago as my reaction to questions of several people how free strongly homotopy algebras can be described and what can be said about the structure of the universal enveloping A(m)-algebra of an L(m)-algebra,…

Algebraic Topology · Mathematics 2007-05-23 Martin Markl

In this paper, we will develop a significantly more general notion of classical Ramsey numbers (extending most other graph-theoretic generalizations) and make some preliminary characterizations of these new Ramsey numbers using simple…

Combinatorics · Mathematics 2025-02-07 Bryce Alan Christopherson

In this paper we give an elementary proof of the Fundamental Theorem of Algebra for polynomials over the rational tropical semi-ring. We prove that, tropically, the rational numbers are algebraically closed. We provide a simple algorithm…

Combinatorics · Mathematics 2007-07-18 Nathan Grigg , Nathan Manwaring

We collect some open problems about minimal presentations of numerical semigroups and, more generally, about defining ideals and free resolutions of their semigroup rings and associated graded rings. We emphasize both long-standing problems…

Combinatorics · Mathematics 2026-05-27 Alessio Moscariello , Alessio Sammartano

In this paper, we consider the problem of determining when two tensor networks are equivalent under a heterogeneous change of basis. In particular, to a string diagram in a certain monoidal category (which we call tensor diagrams), we…

Representation Theory · Mathematics 2017-05-16 Jacob Turner

We show that a tilted algebra $A$ is tame if and only if for each generic root $\dd$ of $A$ and each indecomposable irreducible component $C$ of $\module(A,\dd)$, the field of rational invariants $k(C)^{\GL(\dd)}$ is isomorphic to $k$ or…

Representation Theory · Mathematics 2011-09-15 Calin Chindris

Recently Umirbaev has proved the long-standing Anick conjecture, that is, there exist wild automorphisms of the free associative algebra K<x,y,z> over a field K of characteristic 0. In particular, the well-known Anick automorphism is wild.…

Rings and Algebras · Mathematics 2022-07-06 Vesselin Drensky , Jie-Tai Yu

Term algebras are important objects in computer science and are correspondingly well-studied. A natural generalization is to quotient these algebras by finitely many ground term equations, obtaining what we call almost free algebras. One of…

Logic · Mathematics 2026-04-28 Yifan Jia , Heer Tern Koh , Bakh Khoussainov

We give several examples of tilting-discrete symmetric algebras; in particular, one explores which algebra has tilting-discrete trivial extension. We provide a counter example of the conjecture stating any {\tau} -tilting finite symmetric…

Representation Theory · Mathematics 2025-11-11 Takuma Aihara

For an abelian variety $A$ over a finitely generated field $K$ of characteristic $p > 0$, we prove that the algebraic rank of $A$ is at most a suitably defined analytic rank. Moreover, we prove that equality, i.e., the BSD rank conjecture,…

Algebraic Geometry · Mathematics 2025-08-04 Veronika Ertl , Timo Keller , Yanshuai Qin

We consider an evolution algebra which corresponds to a bisexual population with a set of females partitioned into finitely many different types and the males having only one type. We study basic properties of the algebra. This algebra is…

Commutative Algebra · Mathematics 2013-07-19 M. Ladra , U. A. Rozikov