Surface Defects in the ๐ฉ=2 Lens Space Index and Elliptic Integrability
Abstract
We determine the surface-defect difference operators of the 4d ๐ฉ=2 lens space index for class ๐ฎ theories of type ANโ1 on (๐3/โคr)ร๐1. For generic fugacities (p,q,t) and arbitrary rank N, orbifold order r and discrete holonomies, their coefficients are finite products of theta functions with nomes pr and qr. After an explicit gauge transformation, Gaussian in the holonomies, each operator factorizes into two elliptic Ruijsenaars--Schneider-type operators with step pq, one with nome pr and one with nome qr, acting on variables glued along a lattice. Using this factorization and a Wronski-type relation, we prove that all the operators commute. We also establish a sufficient criterion for self-adjointness with respect to the bilinear vector multiplet pairing. It applies to the basic mixed operator and, in suitable parameter chambers, to the pure p- and q-type operators; for general mixed operators the contour prescription remains open. These results support the expectations from S-duality.
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BibTeX
@misc{yamazaki2026surface,
title = {{Surface Defects in the $\mathcalN=2$ Lens Space Index and Elliptic Integrability}},
author = {Masahito Yamazaki},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.30849},
eprint = {2610.30849},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.30849},
}
RIS
TY - UNPB
TI - Surface Defects in the ๐ฉ=2 Lens Space Index and Elliptic Integrability
AU - Masahito Yamazaki
PY - 2026
DA - 2026/10/22
PB - arXiv
DO - 10.48550/arxiv.2610.30849
UR - https://arxiv.org/abs/2610.30849
AB - We determine the surface-defect difference operators of the 4d ๐ฉ=2 lens space index for class ๐ฎ theories of type A_Nโ1 on (๐^3/โค_r)ร๐^1. For generic fugacities (p,q,t) and arbitrary rank N, orbifold order r and discrete holonomies, their coefficients are finite products of theta functions with nomes p^r and q^r. After an explicit gauge transformation, Gaussian in the holonomies, each operator factorizes into two elliptic Ruijsenaars--Schneider-type operators with step pq, one with nome p^r and one with nome q^r, acting on variables glued along a lattice. Using this factorization and a Wronski-type relation, we prove that all the operators commute. We also establish a sufficient criterion for self-adjointness with respect to the bilinear vector multiplet pairing. It applies to the basic mixed operator and, in suitable parameter chambers, to the pure p- and q-type operators; for general mixed operators the contour prescription remains open. These results support the expectations from S-duality.
ER -