The quest to understand three-body dynamics from first-principle QCD includes the study of non-resonant and resonant systems. The isospin I=2 system is of particular interest having no three-body resonance but featuring a resonance in a sub-channel, while also being a coupled-channel problem. In this study, we calculate the finite-volume spectrum from lattice QC at two different pion masses, map the amplitude to the infinite volume through a generalized FVU three-body quantization condition, investigate the limit of a narrow ρ, and compare with an effective Lagrangian prediction at leading order. Chiral extrapolations between different pion masses are performed.
@article{arxiv.2601.16916,
title = {Coupled-channel approach to isotensor $\pi\pi\pi$ scattering from lattice QCD},
author = {Yuchuan Feng and Chris Culver and Michael Döring and Maxim Mai and Andrei Alexandru and Frank X. Lee},
journal= {arXiv preprint arXiv:2601.16916},
year = {2026}
}