Phase transitions on C*-algebras from actions of congruence monoids on rings of algebraic integers

Bruce, C. (2021) Phase transitions on C*-algebras from actions of congruence monoids on rings of algebraic integers. International Mathematics Research Notices, 2021(5), pp. 3653-3697. (doi: 10.1093/imrn/rnaa056)

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Abstract

We compute the KMS (equilibrium) states for the canonical time evolution on C*-algebras from actions of congruence monoids on rings of algebraic integers. We show that for each β∈[1,2]⁠, there is a unique KMSβ state, and we prove that it is a factor state of type III1⁠. There are phase transitions at β=2 and β=∞ involving a quotient of a ray class group. Our computation of KMS and ground states generalizes the results of Cuntz, Deninger, and Laca for the full ax+b-semigroup over a ring of integers, and our type classification generalizes a result of Laca and Neshveyev in the case of the rational numbers and a result of Neshveyev in the case of arbitrary number fields.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Bruce, Dr Chris
Authors: Bruce, C.
College/School:College of Science and Engineering > School of Mathematics and Statistics
Journal Name:International Mathematics Research Notices
Publisher:Oxford University Press
ISSN:1073-7928
ISSN (Online):1687-0247
Published Online:21 April 2020

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