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Given a topologically free action of a countable group $G$ on a compact metric space $X$, there is a canonical correspondence between continuous 1-cocycles for this group action and diagonal 1-parameter groups of automorphisms of the…

Operator Algebras · Mathematics 2022-10-04 Johannes Christensen , Stefaan Vaes

A systematic theory of product and diagonal states is developed for tensor products of $\mathbb Z_2$-graded $*$-algebras, as well as $\mathbb Z_2$-graded $C^*$-algebras. As a preliminary step to achieve this goal, we provide the…

Operator Algebras · Mathematics 2020-12-18 Vitonofrio Crismale , Rocco Duvenhage , Francesco Fidaleo

In this paper, we study KMS states for the gauge actions on C${}^*$-algebras associated with self-similar sets whose branch points are finite. If the self-similar set does not contain any branch point, the Hutchinson measure gives the…

Operator Algebras · Mathematics 2016-09-07 Tsuyoshi Kajiwara , Yasuo Watatani

We consider operator-algebraic dynamical systems given by actions of the real line on unital $C^*$-algebras, and especially the equilibrium states (or KMS states) of such systems. We are particularly interested in systems built from the…

Operator Algebras · Mathematics 2016-03-21 Astrid an Huef , Iain Raeburn

Let $p\colon \mathcal{A} \to G$ be a saturated Fell bundle over a locally compact, Hausdorff, second countable, {\'e}tale groupoid~$G$, and let $\mathrm{C}^*(G;\mathcal{A})$ denote its full $\mathrm{C}^*$-algebra. We prove an…

Operator Algebras · Mathematics 2023-09-20 Rohit Dilip Holkar , Md Amir Hossain

We study the equilibrium or KMS states of the Toeplitz C*-algebra of a finite higher-rank graph which is reducible. The Toeplitz algebra carries a gauge action of a higher-dimensional torus, and a dynamics arises by choosing an embedding of…

Operator Algebras · Mathematics 2016-10-24 Astrid an Huef , Sooran Kang , Iain Raeburn

We analyse certain Haar systems associated to groupoids obtained by certain natural equivalence relations of dynamical nature on sets like $\{1,2,...,d\}^\mathbb{Z}$, $\{1,2,...,d\}^\mathbb{N}$, $S^1\times S^1$, or $(S^1)^\mathbb{N}$, where…

Dynamical Systems · Mathematics 2019-03-07 Gilles G. de Castro , Artur O. Lopes , Gabriel Mantovani

The paper contains a description of the KMS weights for the one-parameter action on the reduced C*-algebra of a second countable locally compact Hausdorff etale groupoid, arising from a continuous real valued homomorphism satisfying two…

Operator Algebras · Mathematics 2013-06-24 Klaus Thomsen

We introduced a non-symmetric tensor product of any two states or any two representations of Cuntz-Krieger algebras associated with a certain non-cocommutative comultiplication in previous our work. In this paper, we show that a certain set…

Operator Algebras · Mathematics 2008-05-07 Katsunori Kawamura

For every Hilbert bimodule over a C*-algebra, there are natural gauge actions of the circle on the associated Toeplitz algebra and Cuntz-Pimsner algebra, and hence natural dynamics obtained by lifting these gauge actions to actions of the…

Operator Algebras · Mathematics 2014-03-12 Zahra Afsar , Astrid an Huef , Iain Raeburn

We study the KMS states on local quantum Cuntz-Krieger algebras associated to quantum graphs. Using their isomorphism to the Cuntz-Pimsner algebra of the quantum edge correspondence, we show that the general criteria for KMS states can be…

Operator Algebras · Mathematics 2025-07-17 Manish Kumar , Mateusz Wasilewski

An early result of algebraic quantum field theory is that the algebra of any subregion in a QFT is a von Neumann factor of type III$_1$, in which entropy cannot be well-defined because such algebras do not admit a trace or density states.…

High Energy Physics - Theory · Physics 2024-05-02 Shadi Ali Ahmad , Ro Jefferson

This is a study of twisted K-theory on a product space $T \times M$. The twisting comes from a decomposable cup product class which applies the 1-cohomology of $T$ and the 2-cohomology of $M$. In the case of a topological product, we give a…

K-Theory and Homology · Mathematics 2014-05-29 Antti J. Harju

The paper develops a series of tools for the study of KMS-weights on graph C*-algebras and KMS states on their corners. The approach adopts methods and ideas from graph theory, random walks and dynamical systems.

Probability · Mathematics 2018-08-30 Klaus Thomsen

Several authors have recently been studying the equilibrium or KMS states on the Toeplitz algebras of finite higher-rank graphs. For graphs of rank one (that is, for ordinary directed graphs), there is a natural dynamics obtained by lifting…

Operator Algebras · Mathematics 2014-10-02 Astrid an Huef , Sooran Kang , Iain Raeburn

The paper contains a description of the KMS states and ground states of a generalized gauge action on the C*-algebra of a finite graph.

Operator Algebras · Mathematics 2015-05-19 J. Christensen , K. Thomsen

We study the semicrossed product of a finite dimensional C^*-algebra by two types of commuting automorphisms, and identify them with matrix algebras of analytic functions in two variables. We look at the connections with semicrossed…

Operator Algebras · Mathematics 2007-05-23 Mohammed Ridha Alaimia , Justin R. Peters

Using Walters' version of the Ruelle-Perron-Frobenius Theorem we show the existence and uniqueness of KMS states for a certain one-parameter group of automorphisms on a C*-algebra associated to a positively expansive map on a compact metric…

Operator Algebras · Mathematics 2007-05-23 Alex Kumjian , Jean Renault

We present a general construction of KMS states in the framework of perturbative algebraic quantum field theory (pAQFT). Our approach may be understood as an extension of the Schwinger-Keldysh formalism. We obtain in particular the Wightman…

Mathematical Physics · Physics 2014-10-07 Klaus Fredenhagen , Falk Lindner

Given a zero-one matrix A we consider certain one-parameter groups of automorphisms of the Cuntz-Krieger algebra O_A, generalizing the usual gauge group, and depending on a positive continuous function H defined on the Markov space…

Operator Algebras · Mathematics 2007-05-23 Ruy Exel