Universal features of the Abelian Polyakov loop in 1 + 1 dimensions
J. Unmuth-Yockey,
1,*
Jin Zhang,
2,†
A. Bazavov,
3
Y. Meurice,
4
and S.-W. Tsai
2
1
Department of Physics, Syracuse University, Syracuse, New York 13244, USA
2
Department of Physics and Astronomy, University of California, Riverside, California 92521, USA
3
Department of Computational Mathematics, Science and Engineering,
and Department of Physics and Astronomy,
Michigan State University, East Lansing, Michigan 48824, USA
4
Department of Physics and Astronomy, The University of Iowa, Iowa City, Iowa 52242, USA
(Received 8 August 2018; published 27 November 2018)
We show that the Polya kov loop of the two-dimensional lattice Abelian Higgs model can be calculated
using the tensor renormalization group approach. We check the accuracy of the results using standard
Monte Carlo simulations and find good agreement. We show that the energy gap produced by the insertion
of the Polyakov loop obeys universal finite-size scaling which persists in the continuous-time limit. We
briefly discuss the relevance of these results for quantum simulations.
DOI: 10.1103/PhysRevD.98.094511
I. INTRODUCTION
Two-dimensional gauge models have played an impor-
tant role in our understanding of four-dimensional quantum
chromodynamics (QCD). They appear prominently in
several of the Coleman’s Erice lectures [1] and provide
nontrivial model calculations for questions related to
confinement, topology and symmetry breaking. For these
reasons, they are often the first targets when new methods
are developed. There has been a recent interest in using
controlled quantum systems to perform calculations in
lattice gauge theories. The methods used include cold
atoms in optical lattices, trapped ions, and state of the
art quantum computers. Recent efforts have been focused
on the Schwinger model [2–5] and its scalar counterpart the
two-dimensional Abelian Higgs model [6–8].
In recent years, the tensor renormalization group method
(TRG) has been used to reformulate spin and gauge models
with compact field variables into models of discrete integer
(or half-integer) fields [9–13]. This reformulation uses
discrete character expansions which are suitable for quan-
tum computations and can also be used for sampling
purposes [14]. The computation of the tensors involves
integration over the field variables and is manifestly gauge
invariant. The TRG has been used to reformulate the two-
dimensional Abelian Higgs model and find approximations
suitable to implement the model on optical lattices [15].
Recently developed experimental methods involving
Rydberg atoms [16] have been exploited to propose
realistic implementations of the model on a physical ladder
[17]. A key aspect of the proposal in Ref. [17] is that gauge
invariance is maintained exactly, and the Gauss law
constraint need not be enforced “by hand.” This differs
from other quantum simulation approaches [3–8,18,19].
In order to test the ladder implementation, it was proposed
to measure the Polyakov loop [17] for the two-dimensional
Abelian Higgs model. In this process, we found remarkable
finite-size scaling (FSS) properties that to the best of our
knowledge have never been reported. In this article, we
describe these calculations and the interpretation of the
results.
The paper is structured as follows: In Sec. II, the
reformulation of the model in terms of the discrete field-
quantum-number variables is briefly reviewed, and the
Polyakov loop is introduced in terms of the reformulated
variables. We emphasize that the Brout-Englert-Higgs
mode is taken to be infinitely massive and that we are
left with the compact Nambu-Goldstone modes and com-
pact gauge fields. The model that we are considering could
be called “compact scalar electrodynamics”.
In Sec. III, numerical calculations in the relativistic
Lagrangian formulation where space and Euclidean time
are on the same footing are reported. We first show that the
TRG method based on coarse graining and the standard
MonteCarlo(MC) sampling on the original fields are in good
numerical agreement. We then show that the Polyakov loop
defines an energy gap, ΔE, that can be extracted from lattice
configurations with different temporal lengths. We report
on the FSS of this energy gap and present results across a
range of spatial sizes and gauge couplings.
*
jfunmuth@syr.edu
†
jzhan039@ucr.edu
Published by the American Physical Society under the terms of
the Creative Commons Attribution 4.0 International license.
Further distribution of this work must maintain attribution to
the author(s) and the published article’s title, journal citation,
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3
.
PHYSICAL REVIEW D 98, 094511 (2018)
2470-0010=2018=98(9)=094511(10) 094511-1 Published by the American Physical Society