Multipositivity Constrains the Chiral Lagrangian

TL;DR

This paper introduces multipositivity bounds that constrain the chiral Lagrangian's coupling constants, revealing a link between anomalous and nonanomalous sectors in low-energy particle interactions.

Contribution

It presents a new formulation of multipositivity bounds applicable to planar tree-level theories, connecting scattering amplitudes with chiral Lagrangian parameters.

Findings

Certain Wilson coefficients are bounded from below by the chiral anomaly.

The results establish a connection between anomalous and nonanomalous sectors.

Introduces a novel multipositivity bound applicable to any planar tree-level theory.

Abstract

The chiral Lagrangian is a cornerstone of modern particle physics, offering a systematic and quantitative description of low-energy pions. Using tools from the modern scattering amplitudes program, we show that consistent multiparticle dynamics impose novel constraints on the coupling constants of this theory. In the planar limit, these constraints imply that certain Wilson coefficients of the chiral Lagrangian are bounded from below by the chiral anomaly. Our results reveal a subtle connection between the anomalous and nonanomalous sectors of the underlying strong interactions, while introducing a novel formulation of multipositivity bounds that holds for any planar tree-level theory.