Treating Divergent Perturbation Theory: Lessons from Exactly Solvable 2D Models at Large $N$

TL;DR

This paper investigates the operator product expansion in a supersymmetric $O(N)$ model at large $N$, demonstrating the cancellation of infrared renormalon ambiguities with operator contributions, providing insights into non-perturbative effects in supersymmetric theories.

Contribution

It introduces a background field method to explicitly identify operators in the OPE and shows all-order cancellation of renormalon ambiguities in a solvable 2D supersymmetric model.

Findings

Renormalon ambiguities cancel to all orders in the model.

Explicit operator identification in the OPE using a background field approach.

Insights into non-perturbative effects in supersymmetric theories.

Abstract

We consider the operator product expansion (OPE) of correlation functions in the supersymmetric $O(N)$ non-linear sigma model at sub-leading order in the large $N$ limit in order to study the cancellation between ambiguities coming from infrared renormalons and those coming from various operators in the OPE. As has been discussed in the context of supersymmetric Yang-Mills theory in four dimensions, supersymmetry presents a challenge to this cancellation. In a bid to solve this problem we consider $O(N)$ as a toy model. A background field method inspired by Polyakov's treatment of the renormalization of the bosonic $O(N)$ model is used to identify explicit operators in the OPE of the two-point functions of bosonic and fermionic fields in the model. In order to identify the coefficient functions in the OPE, the exact two-point functions at sub-leading order in large $N$ are expanded in powers of the natural infrared length scale. The ambiguities arising from renormalons in the coefficient functions and vacuum expectation values of operators in the OPE are shown to cancel to all orders. The question of supersymmetric Yang-Mills theory without matter remains open.