Multipositivity Constrains the Chiral Lagrangian
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.
Cite
@article{arxiv.2605.21582,
title = {Multipositivity Constrains the Chiral Lagrangian},
author = {Clifford Cheung and Jaehoon Jeong and Pyungwon Ko and Alex Pomarol and Grant N. Remmen and Francesco Sciotti},
journal= {arXiv preprint arXiv:2605.21582},
year = {2026}
}
Comments
10 pages, 2 figures. Ancillary files: Amplitudes and explanatory readme