A Scattering Transform for Noncommutative Instantons
Spencer Tamagni
TL;DR
The work constructs a rigorous bridge between monopole scattering and noncommutative instantons, embedding both in a unified framework tied to infinite Grassmannians and affine Yangians. It introduces instanton scattering matrices $\mathbb{S}(u)$ as semiclassical $R$-matrices whose matrix elements are global functions on instanton moduli, obtained from Ext^1 data and Plücker coordinates, and links them to KP tau-functions. A top-down string/M-theory perspective clarifies the origin of these matrices as brane intersections and Chern-Simons defect data, while a bottom-up fermionic path-integral approach yields explicit determinant formulas and Miura-factorizations. The paper further argues that monopole data can be recovered from the instanton matrices, offering a new nonperturbative route to the $R$-matrix theory of shifted affine Yangians and a geometric realization of double affine Grassmannian slices. Together, these results provide new tools and conjectures for noncommutative gauge theories, integrable systems, and geometric representation theory, with broad implications for the interplay between physics and advanced algebraic structures.
Abstract
We give a detailed and mathematically rigorous analysis of the path integrals of chiral fermions supported on holomorphic curves on $T^* \mathbb{C}$ in a general noncommutative instanton background. It is shown that such path integrals can be interpreted as computing instanton analogs of matrix coefficients of monopole scattering matrices. Generalizing the known relation between monopole scattering matrices and $R$-matrices of (shifted) Yangians $\mathsf{Y}(\mathfrak{gl}_r)$, our formalism gives rise to a novel geometric method to calculate $R$-matrices of (shifted) affine Yangians $\mathsf{Y}(\widehat{\mathfrak{gl}}_r)$. This may also be viewed as an explicit description of double affine Grassmannian slices by $\infty \times \infty$ matrices, compatible with factorization. Our approach unifies a number of earlier results in the literature, and also leads to interesting new results and conjectures.
