Characterizing linear mappings through zero products or zero Jordan products

Periodica Mathematica Hungarica - Let $${\mathcal {A}}$$ be a $$*$$ -algebra and $${{\mathcal {M}}}$$ be a $$*$$ - $${\mathcal {A}}$$ -bimodule. We study the local properties of $$*$$ -derivations...     

Paranormal measurable operators affiliated with a semifinite von Neumann algebra. II

Positivity - Let $${{\mathcal {M}}}$$ be a von Neumann algebra of operators on a Hilbert space $${\mathcal {H}}$$ and $$\tau $$ be a faithful normal semifinite trace on $$\mathcal {M}$$ . Let...     

Idempotent Completion of n-Angulated Categories

Applied Categorical Structures - Let $${\mathcal {C}}$$ be an n-angulated category. We prove that its idempotent completion $$\widetilde{{\mathcal {C}}}$$ admits a unique n-angulated structure such...     

On minimax robust testing of composite hypotheses on Poisson process intensity

Statistical Inference for Stochastic Processes - The problem on the minimax testing of a Poisson process intensity is considered. For a given disjoint sets $${{\mathcal {S}}}_T$$ and $${{\mathcal...     

Fast convergence of inertial dynamics and algorithms with asymptotic vanishing viscosity

Mathematical Programming - In a Hilbert space setting $${{\mathcal {H}}}$$ , we study the fast convergence properties as $$t \rightarrow + \infty $$ of the trajectories of the second-order...     

Multiple expansions of real numbers with digits set $$\left\{ 0,1,q\right\} $$ 0 , 1 , q

Mathematische Zeitschrift - For $$q>1$$ we consider expansions in base q with digits set $$\left\{ 0,1,q\right\} $$ . Let $${{\mathcal {U}}}_q$$ be the set of points which have a unique...     

More on Bounding Introspection in Modal Nonmonotonic Logics

Abstract By we denote the set of all propositional formulas. Let be the set of all clauses. Define . In Sec. 2 of this paper we prove that for normal modal logics , the notions of -expansions and -expansions coincide. In Sec. 3, we prove that if I consists of default clauses then the notions of -expansions for I and -expansions for I coincide. To this end, we first show, in Sec. 3, that the notion of -expansions for I is the same as that of -expansions for I. The project is supported by NSFC     

Unbounded Induced Representations of ∗-Algebras

Induced representations of *-algebras by unbounded operators in Hilbert space are investigated. Conditional expectations of a *-algebra ${{\mathcal{A}}}$ onto a unital *-subalgebra ${{\mathcal{B}}}$ are introduced and used to define inner products on the corresponding induced modules. The main part of the paper is concerned with group graded *-algebras ${{\mathcal{A}}}=\oplus_{g\in G}{{\mathcal{A}}}_g$ for which the *-subalgebra ${{\mathcal{B}}}:={{\mathcal{A}}}_e$ is commutative. Then the canonical projection $p:{{\mathcal{A}}}\to{{\mathcal{B}}}$ is a conditional expectation and there is a partial action of the group G on the set ${{\mathcal{B}}}p$ of all characters of ${{\mathcal{B}}}$ which are nonnegative on the cone $\sum{{\mathcal{A}}}^2{{\mathcal{A}}}p{{\mathcal{B}}}.$ The complete Mackey theory is developed for *-representations of ${{\mathcal{A}}}$ which are induced from characters of ${{\widehat{{{\mathcal{B}}}}^+}}.$ Systems of imprimitivity are defined and two versions of the Imprimitivity Theorem are proved in this context. A concept of well-behaved *-representations of such *-algebras ${{\mathcal{A}}}$ is introduced and studied. It is shown that well-behaved representations are direct sums of cyclic well-behaved representations and that induced representations of well-behaved representations are again well-behaved. The theory applies to a large variety of examples. For important examples such as the Weyl algebra, enveloping algebras of the Lie algebras su(2), su(1,1), and of the Virasoro algebra, and *-algebras generated by dynamical systems our theory is carried out in great detail.     

Transitivity of Jordan Algebras of Linear Operators: On Two Questions by Grünenfelder, Omladič and Radjavi

Let be a Jordan algebra of linear operators on a vector space over a field of characteristic different from 2. In this short note, we show that (1) if is 2-transitive, then it is dense, and (2) if is n-transitive, n ≥ 1, then a nonzero Jordan ideal of is also n-transitive. These answer two questions posed by Grünenfelder, Omladič and Radjavi. The second author was partially supported by National Science Council, Taiwan, grant #095- 2811-M-006-005.     

On the Topological Stable Rank of a Noncommutative Version of the Disc Algebra

Based on a bounded approximate version of LU decomposition, we calculate the topological stable rank of \({{\mathcal {A}}}_{{\mathcal {N}}}\), which is a noncommutative version of the disc algebra. In addition, a general characterization of the maximal two-sided ideals of \({{\mathcal {A}}}_{{\mathcal {N}}}\) will be obtained.     

Codimension two singularities for representations of extended Dynkin quivers

Let M and N be two representations of an extended Dynkin quiver such that the orbit of N is contained in the orbit closure and has codimension two. We show that the pointed variety is smoothly equivalent to a simple surface singularity of type A _n , or to the cone over a rational normal curve.     

On the homotopy fixed point sets of circle actions on product spaces

Archiv der Mathematik - For arbitrary $$S^{1}$$ -actions on $$S^{m}_{{\mathbb {Q}}}$$ , $$S^{n}_{{\mathbb {Q}}}$$ , and $$S^{m}_{{\mathbb {Q}}}\times S^{n}_{{\mathbb {Q}}}$$ , we show the...     

On the Spectrum of a Non-Self-Adjoint Quasiperiodic Operator

Doklady Mathematics - We study the operator $$\mathcal{A}$$ acting in $${{l}^{2}}(\mathbb{Z})$$ by the formula $${{(\mathcal{A}u)}_{l}} = {{u}_{{l + 1}}} + {{u}_{{l - 1}}} + \lambda {{e}^{{ - 2\pi...     

The solvability cardinal of the class of polynomials

Aequationes mathematicae - Let G be an Abelian group, and let $${{\mathbb {C}}}^G$$ denote the set of complex valued functions defined on G. A map $$D: {{\mathbb {C}}}^G \rightarrow {{\mathbb...     

Exponent of a finite group of odd order with an involutory automorphism

Let $$w = w(x_1, \ldots , x_n)$$ be a non-trivial word of n-variables. The word map on a group G that corresponds to w is the map $$\widetilde{w}: G^n\rightarrow G$$ where $$\widetilde{w}((g_1, \ldots , g_n)) := w(g_1, \ldots , g_n)$$ for every sequence $$(g_1, \ldots , g_n)$$ . Let $$\mathcal G$$ be a simple and simply connected group which is defined and split over an infinite field K and let $$G =\mathcal G(K)$$ . For the case when $$w = w_1w_2 w_3 w_4$$ and $$w_1, w_2, w_3, w_4$$ are non-trivial words with independent variables, it has been proved by Hui et al. (Israel J Math 210:81–100, 2015) that $$G{\setminus } Z(G) \subset {{\text { Im}}}\,\widetilde{w}$$ where Z(G) is the center of the group G and $${{\text { Im}}}\, {\widetilde{w}}$$ is the image of the word map $$\widetilde{w}$$ . For the case when $$G = {{\text {SL}}}_n(K)$$ and $$n \ge 3$$ , in the same paper of Hui et al. (2015) it was shown that the inclusion $$G{\setminus } Z(G)\subset {{\text { Im}}}\,\widetilde{w}$$ holds for a product $$w = w_1w_2 w_3$$ of any three non-trivial words $$ w_1, w_2, w_3$$ with independent variables. Here we extent the latter result for every simple and simply connected group which is defined and split over an infinite field K except the groups of types $$B_2, G_2$$ .     

A Novel Insight into the Perfect Phylogeny Problem

One of the classical problem in computational biology is the character compatibility problem or perfect phylogeny problem. A standard formulation of this problem in terms of two closely related questions is the following. Given a data set consisting of a finite set X and a set

Tame properties of sets and functions definable in weakly o-minimal structures

Let ${{\mathcal{M}}=(M, <, \ldots )}$ be a weakly o-minimal expansion of a dense linear order without endpoints. Some tame properties of sets and functions definable in ${{\mathcal{M}}}$ which hold in o-minimal structures, are examined. One of them is the intermediate value property, say IVP. It is shown that strongly continuous definable functions in ${{\mathcal{M}}}$ satisfy an extended version of IVP. After introducing a weak version of definable connectedness in ${{\mathcal{M}}}$ , we prove that strong cells in ${{\mathcal{M}}}$ are weakly definably connected, so every set definable in ${{\mathcal{M}}}$ is a finite union of its weakly definably connected components, provided that ${{\mathcal{M}}}$ has the strong cell decomposition property. Then, we consider a local continuity property for definable functions in ${{\mathcal{M}}}$ and conclude some results on cell decomposition regarding that property. Finally, we extend the notion of having no dense graph (NDG) which was examined for definable functions in (Dolich et al. in Trans. Am. Math. Soc. 362:1371–1411, 2010) and related to uniform finiteness, definable completeness, and others. We show that every weakly o-minimal structure ${{\mathcal{M}}}$ having cell decomposition, satisfies NDG, i.e. every definable function in ${{\mathcal{M}}}$ has no dense graph.     

On the Range of the Aluthge Transform

Let be the algebra of all bounded linear operators on a complex separable Hilbert space For an operator let be the Aluthge transform of T and we define for all where T = U|T| is a polar decomposition of T. In this short note, we consider an elementary property of the range of Δ. We prove that R(Δ) is neither closed nor dense in However R(Δ) is strongly dense if is infinite dimensional. An erratum to this article is available at .     

The gluing formula of the refined analytic torsion for an acyclic Hermitian connection

In the previous study by Huang and Lee (arXiv:1004.1753) we introduced the well-posed boundary conditions ${{\mathcal P}_{-, {\mathcal L}_{0}}}$ and ${{\mathcal P}_{+, {\mathcal L}_{1}}}$ for the odd signature operator to define the refined analytic torsion on a compact manifold with boundary. In this paper we discuss the gluing formula of the refined analytic torsion for an acyclic Hermitian connection with respect to the boundary conditions ${{\mathcal P}_{-, {\mathcal L}_{0}}}$ and ${{\mathcal P}_{+, {\mathcal L}_{1}}}$ . In this case the refined analytic torsion consists of the Ray-Singer analytic torsion, the eta invariant and the values of the zeta functions at zero. We first compare the Ray-Singer analytic torsion and eta invariant subject to the boundary condition ${{\mathcal P}_{-, {\mathcal L}_{0}}}$ or ${{\mathcal P}_{+, {\mathcal L}_{1}}}$ with the Ray-Singer analytic torsion subject to the relative (or absolute) boundary condition and eta invariant subject to the APS boundary condition on a compact manifold with boundary. Using these results together with the well known gluing formula of the Ray-Singer analytic torsion subject to the relative and absolute boundary conditions and eta invariant subject to the APS boundary condition, we obtain the main result.     

Height of a Superposition

We observe that, given a poset ${\left( {E,{\user1{\mathcal{R}}}} \right)}$ and a finite covering ${\user1{\mathcal{R}}} = {\user1{\mathcal{R}}}_{1} \cup \cdots \cup {\user1{\mathcal{R}}}_{n} $ of its ordering, the height of the poset does not exceed the natural product of the heights of the corresponding sub-relations: $$\mathfrak{h}{\left( {E,{\user1{\mathcal{R}}}} \right)} \leqslant \mathfrak{h}{\left( {E,{\user1{\mathcal{R}}}_{1} } \right)} \otimes \cdots \otimes \mathfrak{h}{\left( {E,{\user1{\mathcal{R}}}_{n} } \right)}.$$ Conversely for every finite sequence $(\xi_1,\cdots,\xi_n)$ of ordinals, every poset ${\left( {E,{\user1{\mathcal{R}}}} \right)}$ of height at most $\xi_1\otimes\cdots\otimes\xi_n$ admits a partition ${\left( {{\user1{\mathcal{R}}}_{1} , \cdots ,{\user1{\mathcal{R}}}_{n} } \right)}$ of its ordering ${\user1{\mathcal{R}}}$ such that each ${\left( {E,{\user1{\mathcal{R}}}_{k} } \right)}$ has height at most $\xi_k$ . In particular for every finite sequence $(\xi_1,\cdots,\xi_n)$ of ordinals, the ordinal $$\xi _{1} \underline{ \otimes } \cdots \underline{ \otimes } \xi _{n} : = \sup {\left\{ {{\left( {\xi ^{\prime }_{1} \otimes \cdots \otimes \xi ^{\prime }_{n} } \right)} + 1:\xi ^{\prime }_{1} < \xi _{1} , \cdots ,\xi ^{\prime }_{n} < \xi _{n} } \right\}}$$ is the least $\xi$ for which the following partition relation holds $$\mathfrak{H}_{\xi } \to {\left( {\mathfrak{H}_{{\xi _{1} }} , \cdots ,\mathfrak{H}_{{\xi _{n} }} } \right)}^{2} $$ meaning: for every poset ${\left( {A,{\user1{\mathcal{R}}}} \right)}$ of height at least $\xi$ and every finite covering ${\left( {{\user1{\mathcal{R}}}_{1} , \cdots ,{\user1{\mathcal{R}}}_{n} } \right)}$ of its ordering ${\user1{\mathcal{R}}}$ , there is a $k$ for which the relation ${\left( {A,{\user1{\mathcal{R}}}_{k} } \right)}$ has height at least $\xi_k$ . The proof will rely on analogue properties of vertex coverings w.r.t. the natural sum.