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In the past, it has been shown that the Leavitt path algebra $L(E)=L_K(E)$ of a graph $E$ over a field $K$ is left and right noetherian if and only if the graph $E$ is finite and no cycle of $E$ has an exit. If $Q(E)=Q_K(E)$ denotes the…

Rings and Algebras · Mathematics 2013-11-06 Gonzalo Aranda Pino , Lia Vas

We consider the fundamental group $\pi$ of a surface of finite type equipped with the infinite generating set consisting of all simple closed curves. We show that every nilpotent quotient of $\pi$ has finite diameter with respect to the…

Geometric Topology · Mathematics 2012-11-21 Khalid Bou Rabee , Asaf Hadari

We construct a finitely presented, infinite, simple group that acts by homeomorphisms on the circle, but does not admit a non-trivial action by $C^1$-diffeomorphisms on the circle. The group emerges as a group of piecewise projective…

Group Theory · Mathematics 2019-07-03 Yash Lodha

Let A be a simple, sigma-unital, non-unital C*-algebra, with metrizable tracial simplex T(A), which is projection-surjective and injective and has strict comparison of positive elements by traces. Then the following are equivalent: (i) A…

Operator Algebras · Mathematics 2018-04-10 Victor Kaftal , P. W. Ng , Shuang Zhang

We consider how Morita equivalences are compatible with the notion of a corner subring. Namely, we outline a canonical way to replace a corner subring of a given ring with one which is Morita equivalent, and look at how such an equivalence…

Representation Theory · Mathematics 2023-11-01 Raphael Bennett-Tennenhaus

Let $k$ be a field and let $\Lambda$ be a finite dimensional $k$-algebra. We prove that every bounded complex $V^\bullet$ of finitely generated $\Lambda$-modules has a well-defined versal deformation ring $R(\Lambda,V^\bullet)$ which is a…

Representation Theory · Mathematics 2019-03-20 Frauke M. Bleher , Jose A. Velez-Marulanda

It is shown that the crossed product of a unital AH-algebra with slow dimension growth by an endomorphism is purely infinite when it is simple, provided the endomorphism does not leave a trace state invariant and maps the unit to a full…

Operator Algebras · Mathematics 2010-11-04 Klaus Thomsen

We compute the $k$th power-sums (for all $k>0$) over an arbitrary finite unital ring $R$. This unifies and extends the work of Brawley, Carlitz, and Levine for matrix rings [Duke Math. J. 1974], with folklore results for finite fields and…

Rings and Algebras · Mathematics 2019-03-01 Apoorva Khare , Akaki Tikaradze

We consider the possibility of semisimple tensor categories whose fusion rule includes exactly one noninvertible simple object. Conditions are given for the existence or nonexistence of coherent associative structures for such fusion rules,…

Quantum Algebra · Mathematics 2014-10-01 Jacob Siehler

One of the many equivalent formulation of the K\"othe's conjecture is the assertion that there exists no ring which contains two nil right ideals whose sum is not nil. We discuss several consequences of an observation that if the Koethe…

Rings and Algebras · Mathematics 2020-01-30 Peter Kálnai , Jan Žemlička

{Generalizing the notion of nil cleanness from \cite{D13}, in parallel to \cite{DM14}, we define the concept of {\it weak nil cleanness} for an arbitrary ring. Its comprehensive study in different ways is provided as well. A decomposition…

Rings and Algebras · Mathematics 2014-12-18 Simion Breaz , Peter Danchev , Yiqiang Zhou

In this note we analyze the C*-algebra associated with a branched covering both as a groupoid C*-algebra and as a Cuntz-Pimsner algebra. We determine conditions when the algebra is simple and purely infinite. We indicate how to compute the…

Operator Algebras · Mathematics 2007-05-23 Valentin Deaconu , Paul S. Muhly

We continue our investigation, from \cite{dh}, of the ring-theoretic infiniteness properties of ultrapowers of Banach algebras, studying in this paper the notion of being purely infinite. It is well known that a $C^*$-algebra is purely…

Functional Analysis · Mathematics 2022-04-07 Matthew Daws , Bence Horváth

This paper studies the multiplicative ideal structure of commutative rings in which every finitely generated ideal is quasi-projective. Section 2 provides some preliminaries on quasi-projective modules over commutative rings. Section 3…

Commutative Algebra · Mathematics 2016-01-29 J. Abuhlail , M. Jarrar , S. Kabbaj

We investigate prime avoidance for an arbitrary set of prime ideals in a commutative ring. Various necessary and/or sufficient conditions for prime avoidance are given, which yield natural classes of infinite sets of primes that satisfy…

Commutative Algebra · Mathematics 2017-10-17 Justin Chen

In this paper, we consider pure infiniteness of generalized Cuntz-Krieger algebras associated to labeled spaces $(E,\mathcal{L},\mathcal{E})$. It is shown that a $C^*$-algebra $C^*(E,\mathcal{L},\mathcal{E})$ is purely infinite in the sense…

Operator Algebras · Mathematics 2017-03-07 Ja A Jeong , Eun Ji Kang , Gi Hyun Park

Groups of almost upper triangular infinite matrices with entries indexed by integers are studied. It is shown that, when the matrices are over a finite field, these groups admit a nondiscrete totally disconnected, locally compact group…

Group Theory · Mathematics 2019-12-17 Peter Groenhout , Colin D. Reid , George A. Willis

Models of computation operating over the real numbers and computing a larger class of functions compared to the class of general recursive functions invariably introduce a non-finite element of infinite information encoded in an arbitrary…

Computational Complexity · Computer Science 2010-12-20 Hector Zenil

Let k be a field and R a pure subring of the infinite-dimensional polynomial ring k[X1;...]. If R is generated by monomials, then we show that the equality of height and grade holds for all ideals of R. Also, we show R satisfies the weak…

Commutative Algebra · Mathematics 2016-11-04 Mohsen Asgharzadeh , Mehdi Dorreh , Massoud Tousi

We prove the following. Let $R$ be a Noetherian ring, $B$ a finitely generated $R$-algebra, and $A$ a pure $R$-subalgebra of $B$. Then $A$ is finitely generated over $R$.

Commutative Algebra · Mathematics 2010-11-30 Mitsuyasu Hashimoto