Supercritical phase transition on the Toeplitz algebra of $\mathbb N^\times \ltimes \mathbb Z$

Fuente: arXiv
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Main Authors: Laca, Marcelo, Schulz, Tyler
Format: Preprint
Published: 2025
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_version_ 1866909830457851904
author Laca, Marcelo
Schulz, Tyler
author_facet Laca, Marcelo
Schulz, Tyler
contents We study the high-temperature equilibrium for the C*-algebra $\mathcal T (\mathbb N^\times \ltimes \mathbb N)$ recently considered by an Huef, Laca and Raeburn. We show that the simplex of KMS$_β$ states at each inverse temperature $β$ in the critical interval $(0,1]$ is a Bauer simplex whose space of extreme points is homeomorphic to $\mathbb N \sqcup\{\infty\}$. This is in contrast to the uniqueness of equilibrium at high temperature observed in previously considered systems arising from number theory. We also show that quotients of our system exhibit spontaneous symmetry-breaking by finite cyclotomic Galois groups and establish their connection to the Bost-Connes phase transition.
format Preprint
id arxiv_https___arxiv_org_abs_2503_03033
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Supercritical phase transition on the Toeplitz algebra of $\mathbb N^\times \ltimes \mathbb Z$
Laca, Marcelo
Schulz, Tyler
Operator Algebras
Number Theory
45L05, 46L55
We study the high-temperature equilibrium for the C*-algebra $\mathcal T (\mathbb N^\times \ltimes \mathbb N)$ recently considered by an Huef, Laca and Raeburn. We show that the simplex of KMS$_β$ states at each inverse temperature $β$ in the critical interval $(0,1]$ is a Bauer simplex whose space of extreme points is homeomorphic to $\mathbb N \sqcup\{\infty\}$. This is in contrast to the uniqueness of equilibrium at high temperature observed in previously considered systems arising from number theory. We also show that quotients of our system exhibit spontaneous symmetry-breaking by finite cyclotomic Galois groups and establish their connection to the Bost-Connes phase transition.
title Supercritical phase transition on the Toeplitz algebra of $\mathbb N^\times \ltimes \mathbb Z$
topic Operator Algebras
Number Theory
45L05, 46L55
url https://arxiv.org/abs/2503.03033