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We study a form of refined class number formula (resp. type number formula) for maximal orders in totally definite quaternion algebras over real quadratic fields, by taking into consideration the automorphism groups of right ideal classes…

Number Theory · Mathematics 2019-06-04 Qun Li , Jiangwei Xue , Chia-Fu Yu

Some topics concerning the Gould integral are presented here: new results of integrability on finite measure spaces with values in an M-space are given, together with a Radon-Nikodym theorem relative to a Gould-type integral of real…

Functional Analysis · Mathematics 2018-09-27 Domenico Candeloro , Anca Croitoru , Alina Gavrilut , Anna Rita Sambucini

We extend some results of M.G. Krein to the class of entire functions which can be represented as ratios of discrete Cauchy transforms in the plane. As an application we obtain new versions of de Branges' Ordering Theorem for nearly…

Complex Variables · Mathematics 2018-04-03 Evgeny Abakumov , Anton Baranov , Yurii Belov

Let $H$ be an infinite dimensional separable Hilbert space, $B(H)$ the $C^*$-algebra of all bounded linear operators on $H,$ $U(B(H))$ the unitary group of $B(H)$ and ${\cal K}\subset B(H)$ the ideal of compact operators. Let $G$ be a…

Operator Algebras · Mathematics 2025-02-26 Huaxin Lin

We prove that if two homomorphisms from O_{\infty} to a purely infinite simple C*-algebra have the same class in KK-theory, and if either both are unital or both are nonunital, then they are approximately unitarily equivalent. It follows…

funct-an · Mathematics 2008-02-03 Huaxin Lin , N. Christopher Phillips

Suppose $G$ is a finite group. In this paper, we construct an equivalence between the $\infty$-category of algebras over an $N_{\infty}$-operad $\mathcal{O}$ associated to a $G$-indexing system $\mathcal{I}$ and the corresponding…

Algebraic Topology · Mathematics 2026-04-03 Gregoire Marc

This work results from a study of Nicholas Kuhn's paper entitled "Generic representation theory of finite fields in nondescribing characteristic". Our goal is to abstract the categorical structure required to obtain an equivalence between…

Category Theory · Mathematics 2022-10-10 Ross Street

We demonstrate new abstract characterizations for unital and non-unital operator spaces. We characterize unital operator spaces in terms of the cone of accretive operators (operators whose real part is positive). Defining the gauge of an…

Operator Algebras · Mathematics 2020-05-04 Travis B. Russell

Let $\mathcal{G}$ be a countably infinite group of unitary operators on a complex separable Hilbert space $H$. Let $X = \{x_{1},...,x_{r}\}$ and $Y = \{y_{1},...,y_{s}\}$ be finite subsets of $H$, $r < s$, $V_{0} = \bar{span}…

Operator Algebras · Mathematics 2007-05-23 David R. Larson , Wai Shing Tang , Eric Weber

Let G be a finite group, let A be an infinite-dimensional stably finite simple unital C*-algebra, and let \alpha \colon G \to Aut (A) be an action of G on A which has the weak tracial Rokhlin property. Let A^{\alpha} be the fixed point…

Operator Algebras · Mathematics 2019-08-20 M. Ali Asadi-Vasfi , Nasser Golestani , N. Christopher Phillips

Let $l_0$ be the group (with respect to the coordinate-wise addition) of all sequences of real numbers $x=(x_k)_{k=1}^\infty$ that are eventually zero, equipped with the quasi-norm $\|x\|_0={\rm card}\{supp\,x\}$. A description of orbits of…

Functional Analysis · Mathematics 2020-04-01 Sergey Astashkin

We initiate and study the theory of ``real decomposable maps" between real operator systems. Formally, this is new even in the complex case, which hitherto has restricted itself to the case where the systems are complex C*-algebras. We…

Operator Algebras · Mathematics 2026-05-11 David P. Blecher , Christiaan H. Pretorius

P\'olya's Positivstellensatz and Handelman's Positivstellensatz are known to be concrete instances of the abstract Archimedean Representation Theorem for (commutative unital) rings. We generalise the Archimedean Representation Theorem to…

Algebraic Geometry · Mathematics 2023-11-07 Colin Tan

We characterise absolutely dilatable completely positive maps on the space of all bounded operators on a Hilbert space that are also bimodular over a given von Neumann algebra as rotations by a suitable unitary on a larger Hilbert space…

Operator Algebras · Mathematics 2025-04-25 Alexandros Chatzinikolaou , Ivan G. Todorov , Lyudmila Turowska

The paper is devoted to integral quantization, a procedure based on operator-valued measure and resolution of the identity. We insist on covariance properties in the important case where group representation theory is involved. We also…

Quantum Physics · Physics 2019-11-06 Jean Pierre Gazeau , Herve Bergeron

We investigate completely positive maps for an open system interacting with its environment. The families of the initial states for which the reduced dynamics can be described by a completely positive map are identified within the framework…

Quantum Physics · Physics 2014-07-09 Longjiang Liu , D. M. Tong

We present a natural and simple proof of the Radon - Nikodym theorem for measures with values in the space of bounded linear operators on a separable Hilbert space. This space is not separable, that is why it is essential to assume in the…

Functional Analysis · Mathematics 2013-03-04 S. S. Boiko , V. K. Dubovoy , A. Y. Kheifets

If the symmetry, (an operator $J$ satisfying $J=J^*=J^{-1}$) which defines the Krein space, is replaced by a (not necessarily self-adjoint) unitary, then we have the notion of an $S$-space which was introduced by Szafraniec. In this paper,…

Functional Analysis · Mathematics 2024-04-30 Priyabrata Bag , Azad Rohilla , Harsh Trivedi

We define the graph product of unital completely positive maps on a universal graph product of unital C*-algebras and show that it is unital completely positive itself. To accomplish this, we introduce the notion of the non-commutative…

Operator Algebras · Mathematics 2017-07-07 Scott Atkinson

We develop a theory of ordered *-vector spaces with an order unit. We prove fundamental results concerning positive linear functionals and states, and we show that the order (semi)norm on the space of self-adjoint elements admits multiple…

Operator Algebras · Mathematics 2009-06-10 Vern Paulsen , Mark Tomforde