We show that every infinite-dimensional commutative unital C∗-algebra has a Hilbert C∗-module admitting no frames. In particular, this shows that Kasparov’s stabilization theorem for countably generated Hilbert C∗-modules can not be extended to arbitrary Hilbert C∗-modules.

We consider extensions of unital commutative rings. We define an extension R ↪→ S to be a p-extension if every principally generated ideal of S is generated by an element of R. Examples are plentiful and localizations of regular multiplicative sets are p-extensions. We develop the theory of pextensions.

In Hanaki (Graphs Combin 37:1521–1529, 2021), defined the Terwilliger algebras of association schemes over a commutative unital ring. this paper, we call field $${\mathbb {F}}$$ -algebras and study quasi-thin schemes. As main results, determine -dimensions, semisimplicity, Jacobson radicals, algebraic structures

Let B be a unital commutative semi-simple Banach algebra. We study endomorphisms of B which are simultaneously Riesz operators. Clearly compact and power compact endomorphisms are Riesz. Several general theorems about Riesz endomorphisms are proved, and these results are then applied to the question of when Riesz endomorphisms of certain algebras are necessarily power compact.

We provide polynomial time algorithms for deciding equation solvability and identity checking over groups that are semidirect products of two nite Abelian groups. Our main method is to reduce these problems to the sigma equation solvability and sigma equivalence problems over modules for commutative unital rings.

Let R be a commutative complex unital semisimple Banach algebra with the involution ·⋆. Sufficient conditions are given for the existence of a stabilizing solution to the H ∞ Riccati equation when the matricial data has entries from R. Applications to spatially distributed systems are discussed.

By introducing lattice-valued covers of a set, we present a general framework for uniform structures on very general L-valued spaces (for L an integral commutative quantale). By showing, via an intermediate L-valued structure of uniformity, how filters of covers may describe the uniform operators of Hutton, we prove that, when restricted to Girard quantales, this general framework captures Hutt...

We give a spectral theorem for unital representions of Hermitian commutative unital ∗-algebras by possibly unbounded operators in a pre-Hilbert space. A more general result is known for the case in which the ∗-algebra is countably generated. 1. Statement of the Main Result Our main result is the following: Theorem 1. Let π be a unital representation of a Hermitian commutative unital ∗-algebra A...

We show that any pointed, peordered module map BFgr(E)→BFgr(F) between Bowen-Franks modules of finite graphs can be lifted to a unital, graded, diagonal preserving ⁎-homomorphism Lℓ(E)→Lℓ(F) the corresponding Leavitt path algebras over commutative unital ring with involution ℓ. Specializing case when ℓ is field, we establish fullness part Hazrat's conjecture about functor from ℓ-algebras preord...

Let be a Banach algebra and : a derivation. In this paper, it is proved, under certain conditions, that , where is the Jacobson radical of . Moreover, we prove that if is unital and : is a continuous derivation, then ⋂ ⋂ ⋂ , where denotes the set of all primitive ideals such that is commutative, denotes the set of all maximal (modular) ideals such that is commutative, and Φ is the set of all no...