A dichotomy theory for the height functions of the BKT transition

Fuente: arXiv
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Main Author: Lammers, Piet
Format: Preprint
Published: 2022
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_version_ 1866911633602772992
author Lammers, Piet
author_facet Lammers, Piet
contents This text considers the discrete height functions associated with the Berezinskii--Kosterlitz--Thouless transition (BKT) at slope zero. Our main results are as follows. * Sharpness: If the model is localised, then the two-point function (covariance) decays exponentially fast in the distance between the points. * Effective temperature gap: If the model is delocalised, then the variance grows at least as $c\log n$, where $n$ is the distance to the boundary and $c>0$ a universal constant not depending on the temperature. Thus, the effective temperature must jump from $0$ to at least $c$ at the transition point; values in the interval $(0,c)$ are forbidden. * Delocalisation at the transition point: The delocalised phase includes the transition point, in the sense that it is a closed set in the phase diagram in the appropriate topology. These results contribute to the understanding of the regime at and around the transition point which remained largely unexplored. In a follow-up paper, the sharpness derived here is used to establish that the localisation-delocalisation transition is equivalent to the BKT transition in the dual XY and Villain models.
format Preprint
id arxiv_https___arxiv_org_abs_2211_14365
institution arXiv
publishDate 2022
record_format arxiv
spellingShingle A dichotomy theory for the height functions of the BKT transition
Lammers, Piet
Probability
Mathematical Physics
82B20, 82B41 (Primary) 82B30 (Secondary)
This text considers the discrete height functions associated with the Berezinskii--Kosterlitz--Thouless transition (BKT) at slope zero. Our main results are as follows. * Sharpness: If the model is localised, then the two-point function (covariance) decays exponentially fast in the distance between the points. * Effective temperature gap: If the model is delocalised, then the variance grows at least as $c\log n$, where $n$ is the distance to the boundary and $c>0$ a universal constant not depending on the temperature. Thus, the effective temperature must jump from $0$ to at least $c$ at the transition point; values in the interval $(0,c)$ are forbidden. * Delocalisation at the transition point: The delocalised phase includes the transition point, in the sense that it is a closed set in the phase diagram in the appropriate topology. These results contribute to the understanding of the regime at and around the transition point which remained largely unexplored. In a follow-up paper, the sharpness derived here is used to establish that the localisation-delocalisation transition is equivalent to the BKT transition in the dual XY and Villain models.
title A dichotomy theory for the height functions of the BKT transition
topic Probability
Mathematical Physics
82B20, 82B41 (Primary) 82B30 (Secondary)
url https://arxiv.org/abs/2211.14365