Gauge theory and boundary integrability. Part II. Elliptic and trigonometric cases

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Springer

Received: March 28, 2020 Accepted: May 15, 2020 Published: June 12, 2020

Roland Bittleston and David Skinner Department of Applied Mathematics & Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom

E-mail: [email protected], [email protected] Abstract: We consider the mixed topological-holomorphic Chern-Simons theory introduced by Costello, Yamazaki & Witten on a Z2 orbifold. We use this to construct semiclassical solutions of the boundary Yang-Baxter equation in the elliptic and trigonometric cases. A novel feature of the trigonometric case is that the Z2 action lifts to the gauge bundle in a z-dependent way. We construct several examples of K-matrices, and check that they agree with cases appearing in the literature. Keywords: Chern-Simons Theories, Lattice Integrable Models, Wilson, ’t Hooft and Polyakov loops ArXiv ePrint: 1912.13441

c The Authors. Open Access, Article funded by SCOAP3 .

https://doi.org/10.1007/JHEP06(2020)080

JHEP06(2020)080

Gauge theory and boundary integrability. Part II. Elliptic and trigonometric cases

Contents 1 Introduction 1.1 CWY theory 1.2 The boundary Yang-Baxter equation

1 2 4 8 8 9 10

3 Trigonometric 3.1 Trigonometric solutions of the Yang-Baxter equation 3.2 Trigonometric solutions of the boundary Yang-Baxter equation 3.3 Examples of trigonometric solutions 3.4 Generalization to z-dependent automorphisms 3.5 Examples of K-matrices associated to z-dependent automorphisms

13 13 15 16 20 21

4 Comments on uniqueness

23

A Asymptotic behaviour of elliptic K-matrices in the ~ → 0 limit

24

B Asymptotic behaviour of trigonometric K-matrices in the ~ → 0 limit

27

C Determination of allowed automorphisms in the elliptic case

28

D Determination of allowed automorphisms in the trigonometric case

30

E An aside on loop algebras

32

1

Introduction

In [1] rational solutions of the boundary Yang-Baxter equation were generated as the vacuum expectation values of Wilson lines in a mixed topological-holomorphic analogue of Chern-Simons theory on a Z2 -orbifold. This extended the link between gauge theory and quantum integrability developed by Costello, Witten, and Yamazaki in the papers [2–5] to integrable models with boundary. The mixed topological-holomorphic analogue of ChernSimons theory underpinning this link was first proposed by Nekrasov in his Ph.D. thesis [6], see also the related papers [7, 8]. In this paper we expand this construction to elliptic and trigonometric solutions of the boundary Yang-Baxter equation. We begin by reviewing the CWY approach to 2d quantum integrable lattice models. We shall be brief, and refer the reader to [2, 4] for more detailed discussions of the theory

–1–

JHEP06(2020)080

2 Elliptic solutions 2.1 Elliptic solutions of the Yang-Baxter equation 2.2 Elliptic solutions of the boundary Yang-Baxter equation 2.3 Construction of elliptic solutions

1.1

CWY theory

where A(w) = Ax (w)dx + Ay (w)dy + Az¯(w)d¯ z is a partial connection on a G-bundle over M . Note that