Outer Automorphisms on Cuntz Algebras

We prove that if an automorphism on the Cuntz algebra O_n satisfies(S₁) = S₁ for one isometry S₁ of generators S₁, ..., S_n suchthat , , l i n and a complex number with modulus one,then it is outer. In particular, any non trivial automorphismon O_n leaving one generator fixed is outer.     

Artin Group Presentations Arising from Cluster Algebras

In 2003, Fomin and Zelevinsky proved that finite type cluster algebras can be classified by Dynkin diagrams. Then in 2013, Barot and Marsh defined the presentation of a reflection group associated to a Dynkin diagram in terms of an edge-weighted, oriented graph, and proved that this group is invariant (up to isomorphism) under diagram mutations. In this paper, we extend Barot and Marsh’s results to Artin group presentations, defining new generator relations and showing mutation-invariance for these presentations.     

Fixed Points of Compact Quantum Groups Actions on Cuntz Algebras

Given an action of a Compact Quantum Group (CQG) on a finite dimensional Hilbert space, we can construct an action on the associated Cuntz algebra. We study the fixed point algebra of this action, using Kirchberg classification results. Under certain conditions, we prove that the fixed point algebra is purely infinite and simple. We further identify it as a C ^*-algebra, compute its K-theory and prove a “stability property”: the fixed points only depend on the CQG via its fusion rules. We apply the theory to SU _q (N) and illustrate by explicit computations for SU _q (2) and SU _q (3). This construction provides examples of free actions of CQG (or “principal noncommutative bundles”).     

Extensions of Modules over Hopf Algebras Arising from Lie Algebras of Cartan Type

In this paper we prove that there are no self-extensions of simple modules over restricted Lie algebras of Cartan type. The proof given by Andersen for classical Lie algebras not only uses the representation theory of the Lie algebra, but also representations of the corresponding reductive algebraic group. The proof presented in the paper follows in the same spirit by using the construction of a infinite-dimensional Hopf algebra D(G) u( ) containing u( ) as a normal Hopf subalgebra, and the representation theory of this algebra developed in our previous work. Finite-dimensional hyperalgebra analogs D(G _r ) u( ) have also been constructed, and the results are stated in this setting.     

Radial Multiresolution, Cuntz Algebras Representations and an Application to Fractals

We study Bernoulli type convolution measures on attractor sets arising from iterated function systems on R. In particular we examine orthogonality for Hankel frequencies in the Hilbert space of square integrable functions on the attractor coming from a radial multiresolution analysis on R³. A class of fractals emerges from a finite system of contractive affine mappings on the zeros of Bessel functions. We have then fractal measures on one hand and the geometry of radial wavelets on the other hand. More generally, multiresolutions serve as an operator theoretic framework for the study of such selfsimilar structures as wavelets, fractals, and recursive basis algorithms. The purpose of the present paper is to show that this can be done for a certain Bessel–Hankel transform. Submitted: February 20, 2008., Accepted: March 6, 2008.     

从几何代数到高级不变量计算

综述近几年来几何代数和高级不变量计算两方面的主要进展,重点是共形几何代数的背景、思路、发展和对经典几何的高级不变量理论发展的重要作用.     

效应代数上态的存在性

[中国科学A,2011,41(3):279-286]引入了效应代数的表示,给出了可表示与不可表示的效应代数的例子,证明了某些效应代数的可表示性.然而,尚未得到一般效应代数的可表示准则.基于抽象C^*-代数的GNS均造的思想,我们猜测具有足够多的态的抽象效应代数应当是可以表示的.因而,态的存在性与态空间的表示问题对于建立抽象效应代数的表示理论、解决分类问题似乎是至关重要的.本文讨论效应代数上态的存在性和赋值的存在性问题,给出了若干典型的效应代数上态的一般形式与它们的态空间.特别地,证明了可表示效应代数上态的存在性定理,并得到了到态空间与赋值空间的非空凸子集.     

On the Generalized Cartan Matrices Arising from k-th Yau Algebras of Isolated Hypersurface Singularities

Algebras and Representation Theory - Let (V,0) be an isolated hypersurface singularity defined by the holomorphic function $f: (mathbb {C}^{n}, 0)rightarrow (mathbb {C}, 0)$ . The k-th Yau...     

Fermat–Euler Dynamical Systems and the Statistics of Arithmetics of Geometric Progressions

Let n be an integer. A Fermat–Euler dynamical system acts on the set of mod-n residues coprime to n by multiplication by a constant (which is also coprime to n). We study the dependence of the period and the number of orbits of this dynamical system on n. Theorems generalizing Fermat's little theorem, as well as empirical conjectures, are given.     

Finitely Correlated Pure States

We study a w*-dense subset of the translation invariant states on an infinite tensor product algebra , where is a matrix algebra. These "finitely correlated states" are explicitly constructed in terms of a finite dimensional auxiliary algebra and a completely positive map : → . We show that such a state ω is pure if and only if it is extremal periodic and its entropy density vanishes. In this case the auxiliary objects and are uniquely determined by ω, and can be expressed in terms of an isometry between suitable tensor product Hilbert spaces.     

Classically Normal Pure States

A pure state f of a von Neumann algebra is called classically normal if f is normal on any von Neumann subalgebra of on which f is multiplicative. Assuming the continuum hypothesis, a separably represented von Neumann algebra M has classically normal, singular pure states iff there is a central projection p ∈M such that pMp is a factor of type I_∞, II, or III.     

Pure Injective Indecomposable Modules over 1-Domestic String Algebras

We classify indecomposable pure injective modules over 1-domestic string algebras verifying Ringel’s conjecture on their structure.     

Linear functionals on the Cuntz algebra

For a pure state on , which is an extension of a pure state on with the property that if is a corresponding representation, then , induces a unital shift of of the Powers index . We describe states on by using sequences of unit vectors in . We study the linear functionals on the Cuntz algebra whose restrictions are the product pure state on . We find conditions on the sequence of unit vectors for which the corresponding linear functionals on become states under these conditions.

     

Representation Theory of some Infinite-dimensional Algebras Arising in Continuously Controlled Algebra and Topology

In this paper we determine the representation type of some algebras of infinite matrices continuously controlled at infinity by a compact metrizable space. We explicitly classify their finitely presented modules in the finite and tame cases. The algebra of row-column-finite (or locally finite) matrices over an arbitrary field is one of the algebras considered in this paper, its representation type is shown to be finite.Received October 2003     

(n-1)-半单的n-李代数的几何描述

证明了实数域上(n-1)-半单的(n+1)维n-李代数A是n维欧氏空间的Lorentz群O(p,n-p)与n维Abel正规子群的半直积的n-李代数.且当p=0时,A是n维欧氏空间的等距变换群的n-李代数.并提出了关于(n-1)-半单的(n+1)维n-李代数的外导子的物理应用与几何应用问题.