Records from the S-Matrix Marathon: Asymptotic Observables
Abstract
These lectures introduce the notion of asymptotic observables, which are classes of measurable quantities predicted by quantum field theory. In gapped theories with trivial infrared dynamics, these include scattering amplitudes, expectation values of operators approaching infinity, inclusive cross sections, etc. We argue for a unified picture in which various asymptotic observables are related by analytic continuation embodying new versions of crossing symmetry. As an application, we discuss the exponentiation of infrared divergences for inclusive observables in Quantum Electrodynamics using time-folded contours. Finally, we outline prospects for a systematic study of analyticity properties of asymptotic observables using the Fourier-Bros-Iagolnitzer transform. These notes are based on a series of lectures held during the S-Matrix Marathon workshop at the Institute for Advanced Study on 11-22 March 2024.
Keywords
Cite
@article{arxiv.2502.13021,
title = {Records from the S-Matrix Marathon: Asymptotic Observables},
author = {Simon Caron-Huot and Mathieu Giroux and Holmfridur S. Hannesdottir and Sebastian Mizera and Celina Pasiecznik},
journal= {arXiv preprint arXiv:2502.13021},
year = {2025}
}
Comments
A chapter to be published by Springer Lecture Notes in Physics