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Let $H$ be a separable Hilbert space with a fixed orthonormal basis. Let $\mathbb B^{(k)}(H)$ denote the set of operators, whose matrices have no more than $k$ non-zero entries in each line and in each column. The closure of the union (over…

Operator Algebras · Mathematics 2018-08-21 Vladimir Manuilov

We expand on some invariants used for classifying nonselfadjoint operator algebras. Specifically to nonselfadjoint operator algebras which have a conditional expectation onto a commutative diagonal we construct an edge-colored directed…

Operator Algebras · Mathematics 2013-07-23 Benton Duncan

We overview the development of Fra\"{i}ss\'e theory in the setting of continuous model theory, and some of the its recent applications to $\mathrm{C}^*$-algebra theory and functional analysis.

Operator Algebras · Mathematics 2022-11-03 Alessandro Vignati

We use computational linear algebra and commutative algebra to study spaces of relations satisfied by quadrilinear operations. The relations are analogues of associativity in the sense that they are quadratic (every term involves two…

Rings and Algebras · Mathematics 2025-08-01 Murray R. Bremner , Juana Sánchez-Ortega

We use the Fock semicrossed product to define an operator algebra associated to a module over an integral domain. We consider the $C^*$-envelope of the semicrossed product, and then consider properties of these algebras as models for…

Operator Algebras · Mathematics 2016-07-29 Benton L. Duncan

This survey provides an elementary introduction to operads and to their applications in homotopical algebra. The aim is to explain how the notion of an operad was prompted by the necessity to have an algebraic object which encodes higher…

Algebraic Topology · Mathematics 2012-02-16 Bruno Vallette

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

Given a group G, we construct, in a canonical way, an inverse semigroup S(G) associated to G. The actions of S(G) are shown to be in one-to-one correspondence with the partial actions of G, both in the case of actions on a set, and that of…

funct-an · Mathematics 2008-02-03 Ruy Exel

We introduce quasi-Hopf $*$-algebras i.e. quasi-Hopf algebras equipped with a conjugation (star) operation. The definition of quasi-Hopf $*$-algebras proposed ensures that the class of quasi-Hopf $*$-algebras is closed under twisting and…

Quantum Algebra · Mathematics 2007-05-23 M. D. Gould , T. Lekatsas

It is shown that the class of Fredholm operators over an arbitrary unital $C^{*}$--algebra, which may not admit adjoint ones, can be extended in such a way that this class of compact operators, used in the definition of the class of…

K-Theory and Homology · Mathematics 2007-05-23 Anwar A. Irmatov , Alexandr S. Mishchenko

We study $\mathcal{O}$-operators of associative conformal algebras with respect to conformal bimodules. As natural generalizations of $\mathcal{O}$-operators and dendriform conformal algebras, we introduce the notions of twisted Rota-Baxter…

Rings and Algebras · Mathematics 2022-07-13 Lamei Yuan

We bring an abstract model theory perspective to interpolation. We ask, what is the role of interpolation in the study of extensions of first order logic, such as infinitary logics, generalized quantifiers and higher order logics? The…

Logic · Mathematics 2025-07-28 Jouko Väänänen

Motivated by deformation quantization we consider $^*$-algebras over ordered rings and their deformations: we investigate formal associative deformations compatible with the $^*$-involution and discuss a cohomological description in terms…

Quantum Algebra · Mathematics 2007-05-23 Henrique Bursztyn , Stefan Waldmann

We study various operator homological properties of the Fourier algebra $A(G)$ of a locally compact group $G$. Establishing the converse of two results of Ruan and Xu, we show that $A(G)$ is relatively operator 1-projective if and only if…

Operator Algebras · Mathematics 2018-05-24 Jason Crann , Zsolt Tanko

A unital $C^*$-algebra is called $N$-subhomogeneous if its irreducible representations are finite dimensional with dimension at most $N$. We extend this notion to operator systems, replacing irreducible representations by boundary…

Operator Algebras · Mathematics 2023-02-10 Ran Kiri

We will investigate the norm closure of the unitary and similarity orbits of normal operators in unital, simple, purely infinite C*-algebras. An operator theoretic proof will be given to the classification of when two normal operators are…

Operator Algebras · Mathematics 2013-05-28 Paul Skoufranis

The aim of this paper is to show that even if the natural algebraic semantic for modal (normal) logic is modal algebra, the more general class of subordination algebras (roughly speaking, the non symmetric contact algebras) is adequate too…

Logic · Mathematics 2020-06-17 Laurent De Rudder , Georges Hansoul , Valentine Stetenfeld

We give an exposition on the current status of classification of operator algebraic conformal field theories. We explain roles of complete rationality and alpha-induction for nets of subfactors in such a classification and present the…

Operator Algebras · Mathematics 2007-05-23 Yasuyuki Kawahigashi

Certain $*$-semigroups are associated with the universal $C^*$-algebra generated by a partial isometry, which is itself the universal $C^*$-algebra of a $*$-semigroup. A fundamental role for a $*$-structure on a semigroup is emphasized, and…

Operator Algebras · Mathematics 2014-06-03 Berndt Brenken

In this paper, we investigate the relative operator entropies in the more general settings of C*-algebras, real C*-algebras and JC-algebras. We show that all the operator inequalities on relative operator entropies still hold in these…

Operator Algebras · Mathematics 2020-12-24 Shuzhou Wang , Zhenhua Wang