BKP-Affine Coordinates and Emergent Geometry of Generalized Brézin-Gross-Witten Tau-Functions
Zhiyuan Wang, Chenglang Yang, Qingsheng Zhang
TL;DR
The paper develops an emergent-geometry framework for generalized Brézin-Gross-Witten BKP tau-functions by deriving a spectral curve and its special deformation from Virasoro constraints. It provides explicit BKP-affine coordinates and a generating-series description that yield a closed formula for connected n-point functions, and it demonstrates that the Eynard-Orantin topological recursion on the emergent spectral curve reproduces these correlators. A quantum spectral curve of type B is constructed via Kac-Schwarz operators, linking the BKP data to a Schrödinger-type equation whose semiclassical limit matches the classical curve $x^2y^2=x^2+S^2$. Together, these results connect BKP tau-function techniques, topological recursion, and quantum curve concepts, offering concrete computational tools for BGW-related enumerative geometries and highlighting the role of BKP-affine coordinates in emergent geometry.
Abstract
Following Zhou's framework, we consider the emergent geometry of the generalized Brézin-Gross-Witten models whose partition functions are known to be a family of tau-functions of the BKP hierarchy. More precisely, we construct a spectral curve together with its special deformation, and show that the Eynard-Orantin topological recursion on this spectral curve emerges naturally from the Virasoro constraints for the generalized BGW tau-functions. Moreover, we give the explicit expressions for the BKP-affine coordinates of these tau-functions and their generating series. The BKP-affine coordinates and the topological recursion provide two different approaches towards the concrete computations of the connected $n$-point functions. Finally, we show that the quantum spectral curve of type $B$ in the sense of Gukov-Sułkowski emerges from the BKP-affine coordinates and Eynard-Orantin topological recursion.
