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By considering the general properties of approximate units in differentiable algebras, we are able to present a unified approach to characterising completeness of spectral metric spaces, existence of connections on modules, and the lifting…

Operator Algebras · Mathematics 2016-10-24 Bram Mesland , Adam Rennie

By introducing a notion of smooth connection for unbounded $KK$-cycles, we show that the Kasparov product of such cycles can be defined directly, by an algebraic formula. In order to achieve this it is necessary to develop a framework of…

K-Theory and Homology · Mathematics 2014-04-18 Bram Mesland

We present a definition of indefinite Kasparov modules, a generalisation of unbounded Kasparov modules modelling non-symmetric and non-elliptic (e.g. hyperbolic) operators. Our main theorem shows that to each indefinite Kasparov module we…

K-Theory and Homology · Mathematics 2016-02-16 Koen van den Dungen , Adam Rennie

Kucerovsky's theorem provides a method for recognizing the interior Kasparov product of selfadjoint unbounded cycles. In this paper we extend Kucerovsky's theorem to the non-selfadjoint setting by replacing unbounded Kasparov modules with…

Operator Algebras · Mathematics 2017-09-27 Jens Kaad , Walter D. van Suijlekom

We construct an unbounded representative for the shriek class associated to the embeddings of spheres into Euclidean space. We equip this unbounded Kasparov cycle with a connection and compute the unbounded Kasparov product with the Dirac…

Quantum Algebra · Mathematics 2019-11-19 Walter D. van Suijlekom , Luuk S. Verhoeven

In this paper we introduce the curvature of densely defined universal connections on Hilbert $C^{*}$-modules relative to a spectral triple (or unbounded Kasparov module), obtaining a well-defined curvature operator. Fixing the spectral…

Operator Algebras · Mathematics 2019-11-13 Bram Mesland , Adam Rennie , Walter D. van Suijlekom

In the context of the Kasparov product in unbounded KK-theory, a well-known theorem by Kucerovsky provides sufficient conditions for an unbounded Kasparov module to represent the (internal) Kasparov product of two other unbounded Kasparov…

K-Theory and Homology · Mathematics 2023-07-03 Koen van den Dungen

We extend unbounded Kasparov theory to encompass conformal group and quantum group equivariance. This new framework allows us to treat conformal actions on both manifolds and noncommutative spaces. As examples, we present unbounded…

Operator Algebras · Mathematics 2026-02-24 Ada Masters , Adam Rennie

We present a fairly general construction of unbounded representatives for the interior Kasparov product. As a main tool we develop a theory of C^1-connections on operator * modules; we do not require any smoothness assumptions; our…

Operator Algebras · Mathematics 2013-09-12 Jens Kaad , Matthias Lesch

In the founding paper on unbounded $KK$-theory it was established by Baaj and Julg that the bounded transform, which associates a class in $KK$-theory to any unbounded Kasparov module, is a surjective homomorphism (under a separability…

K-Theory and Homology · Mathematics 2020-08-25 Jens Kaad

We improve our previous results on indefinite Kasparov modules, which provide a generalisation of unbounded Kasparov modules modelling non-symmetric and non-elliptic (e.g. hyperbolic) operators. In particular, we can weaken the assumptions…

K-Theory and Homology · Mathematics 2019-10-03 Koen van den Dungen

A regular symmetric operator on a Hilbert module is self-adjoint whenever there exists a suitable approximate identity. We say an operator is 'locally bounded' if the composition of the operator with each element in the approximate identity…

Operator Algebras · Mathematics 2019-09-16 Koen van den Dungen

We introduce a notion of Morita equivalence for non-selfadjoint operator algebras equipped with a completely isometric involution (operator *-algebras). We then show that the unbounded Kasparov product by a Morita equivalence bimodule…

K-Theory and Homology · Mathematics 2016-12-28 Jens Kaad

We show how to equip the crossed product between a group of polynomial growth and a compact quantum metric space with a compact quantum metric space structure. When the quantum metric on the base space arises from a spectral triple, which…

Operator Algebras · Mathematics 2024-12-02 Are Austad , Jens Kaad , David Kyed

We explore factorizations of noncommutative Riemannian spin geometries over commutative base manifolds in unbounded KK-theory. After setting up the general formalism of unbounded KK-theory and improving upon the construction of internal…

K-Theory and Homology · Mathematics 2016-10-24 Simon Brain , Bram Mesland , Walter D. van Suijlekom

Starting with a spectral triple on a unital $C^{*}$-algebra $A$ with an action of a discrete group $G$, if the action is uniformly bounded (in a Lipschitz sense) a spectral triple on the reduced crossed product $C^{*}$-algebra $A\rtimes_{r}…

Operator Algebras · Mathematics 2022-08-30 P. Antonini , D. Guido , T. Isola , A. Rubin

This article is about erroneous attempts to weaken the standard definition of unbounded Kasparov module (or spectral triple). We present counterexamples to claims in the literature that Fredholm modules can be obtained from these weaker…

K-Theory and Homology · Mathematics 2019-11-28 I. Forsyth , B. Mesland , A. Rennie

We give a construction allowing to lift spectral triples to crossed products by Hilbert bimodules. The spectral triple one obtains is a concrete unbounded representative of the Kasparov product of the spectral triple and the…

Operator Algebras · Mathematics 2013-10-23 Olivier Gabriel , Martin Grensing

The Kasparov absorption (or stabilization) theorem states that any countably generated Hilbert C*-module is isomorphic to a direct summand in the standard module of square summable sequences in the base C*-algebra. In this paper, this…

Operator Algebras · Mathematics 2014-07-08 Jens Kaad

We study strongly graded vertex algebras and their strongly graded modules, which are conformal vertex algebras and their modules with a second, compatible grading by an abelian group satisfying certain grading restriction conditions. We…

Quantum Algebra · Mathematics 2013-02-25 Jinwei Yang
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