The ChPT: top-down and bottom-up

TL;DR

This paper systematically studies higher-derivative corrections in Chiral perturbation theory (ChPT), applying new S-matrix methods to analyze its amplitude structure and explore theoretical simplifications and connections to string theory.

Contribution

It introduces a novel application of S-matrix techniques to ChPT, analyzing its formal structure and potential simplifications, and compares it with string theory related Z-functions.

Findings

Identification of formal structures in ChPT amplitudes

Application of Kleiss-Kuijf and BCJ relations to ChPT

Comparison of ChPT amplitudes with string theory Z-functions

Abstract

In this work, higher-derivative corrections of the non-linear sigma model of both even and odd intrinsic-parity sectors are systematically studied, focusing on ordered amplitudes of flavor scalars in massless limit. It should correspond to a theory known as Chiral perturbation theory (ChPT) without external sources and with only single-trace operators. We briefly overview its formal development and apply new S-matrix methods to its amplitude constructions. The bottom-up analysis of the tree-level amplitudes of different orders and multiplicities focuses on the formal structure of general ChPT. Possible theoretical simplifications based on the Kleiss-Kuijf and Bern-Carrasco-Johansson relations are presented. Finally, in the same context, the comparison with the so-called Z-function, which is connected with string theory, is also discussed.