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We introduce a notion of antipode for monoidal (complete) decomposition spaces, inducing a notion of weak antipode for their incidence bialgebras. In the connected case, this recovers the usual notion of antipode in Hopf algebras. In the…

Algebraic Topology · Mathematics 2021-03-31 Louis Carlier , Joachim Kock

A refined notion of curvature for a linear system of Hermitian vector spaces, in the sense of Grothendieck, leads to the unitary classification of a large class of analytic Hilbert modules. Specifically, we study Hilbert sub-modules, for…

Spectral Theory · Mathematics 2009-09-11 Shibananda Biswas , Gadadhar Misra , Mihai Putinar

In this paper we determine extensions of higher degree between indecomposable modules over gentle algebras. In particular, our results show how such extensions either eventually vanish or become periodic. We give a geometric interpretation…

Representation Theory · Mathematics 2019-06-13 Karin Baur , Sibylle Schroll

In this article, we study Dorroh extensions of algebras and Dorroh extensions of coalgebras. Their structures are described. Some properties of these extensions are presented. We also introduce the finite duals of algebras and modules which…

Rings and Algebras · Mathematics 2020-07-07 Lan You , Hui-Xiang Chen

We develop the concept of operators in Hilbert spaces which are similar to their adjoints via antiunitary operators, the latter being not necessarily involutive. We discuss extension theory, refined polar and singular-value decompositions,…

Functional Analysis · Mathematics 2023-04-14 M. Cristina Câmara , David Krejcirik

In this article we study extensions of Z_2-graded L_infinity algebras on a vector space of two even and one odd dimension. In particular, we determine all extensions of a super Lie algebra as an L_infinity algebra. Our convention on the…

Quantum Algebra · Mathematics 2007-05-23 Alice Fialowski , Michael Penkava

We show that a central extension of locally quasiconvex subgroup separable hyperbolic group is product separable, so long as it is subgroup separable. We also establish that a central extension of a double coset separable group by a…

Group Theory · Mathematics 2026-03-06 Lawk Mineh

We characterize bijections on matrix spaces (operator algebras) preserving full rank (invertibility) of differences of matrix (operator) pairs in both directions.

Rings and Algebras · Mathematics 2024-02-05 Hans Havlicek , Peter Šemrl

This work presents a rigorous characterization of inner products on the Hilbert space $S_2$ of Hilbert--Schmidt operators. We first deal with a general setting of continuous sesquilinear forms on a Hilbert space $\mathcal H$, and provide a…

Functional Analysis · Mathematics 2025-06-06 Josué I. Rios-Cangas

We extend the classical Stone duality between zero dimensional compact Hausdorff spaces and Boolean algebras. Specifically, we simultaneously remove the zero dimensionality restriction and extend to \'etale groupoids, obtaining a duality…

Logic · Mathematics 2019-11-19 Tristan Bice , Charles Starling

The lack of an inner product structure in Banach spaces yields the motivation to introduce a semi-inner product with a more general axiom system, one missing the requirement for symmetry, unlike the one determing a Hilbert space. We use it…

Metric Geometry · Mathematics 2015-11-11 Ákos G. Horváth , Zsolt Lángi , Margarita Spirova

The aim of this article is to investigate internal actions and split extensions in the variety of hoops. We provide a characterization of split extensions with strong section in terms of strong external actions. Beyond the general setting…

Category Theory · Mathematics 2026-03-31 Manuel Mancini , Giuseppe Metere , Federica Piazza

We compare closed and rigid monoidal categories. Closedness is defined by the tensor product having a right adjoint: the internal hom functor. Rigidity, on the other hand, generalises the duality of finite-dimensional vector spaces. In the…

Category Theory · Mathematics 2026-02-06 Sebastian Halbig , Tony Zorman

In the theory of reproducing kernel Hilbert spaces, weak product spaces generalize the notion of the Hardy space $H^1$. For complete Nevanlinna-Pick spaces $\mathcal H$, we characterize all multipliers of the weak product space $\mathcal H…

Functional Analysis · Mathematics 2022-04-25 Raphaël Clouâtre , Michael Hartz

We construct whole-space extensions of functions in a fractional Sobolev space of order $s\in (0,1)$ and integrability $p\in (0,\infty)$ on an open set $O$ which vanish in a suitable sense on a portion $D$ of the boundary $\partial O$ of…

Functional Analysis · Mathematics 2021-08-17 Sebastian Bechtel

On finite dimensional spaces, it is apparent that an operator is the product of two positive operators if and only if it is similar to a positive operator. Here, the class ${\mathcal L}^{+2}$ of bounded operators on separable infinite…

Functional Analysis · Mathematics 2021-01-27 Maximiliano Contino , Michael A. Dritschel , Alejandra Maestripieri , Stefania Marcantognini

In this paper we work with unital twisted partial actions. We investigate ring theoretic properties of partial crossed products as artinianity, noetherianity, perfect property, semilocalproperty, semiprimary property and we also study the…

Rings and Algebras · Mathematics 2016-03-29 Laerte Bemm , Wagner Cortes

We introduce the algebraic entropy for continuous endomorphisms of locally linearly compact vector spaces over a discrete field, as the natural extension of the algebraic entropy for endomorphisms of discrete vector spaces. We show that the…

Dynamical Systems · Mathematics 2021-01-05 Ilaria Castellano , Anna Giordano Bruno

The theory of product systems both of Hilbert spaces (Arveson systems) and product systems of Hilbert modules has reached a status where it seems appropriate to rest a moment and to have a look at what is known so far and what are open…

Operator Algebras · Mathematics 2017-08-23 Michael Skeide

We study the existence of nontrivial semidualizing DG modules over tensor products of DG algebras over a field. In particular, this gives a lower bound on the number of semidualizing DG modules over the tensor product.

Commutative Algebra · Mathematics 2014-11-26 Hannah Altmann