What can be measured asymptotically?
Abstract
We consider asymptotic observables in quantum field theories in which the S-matrix makes sense. We argue that in addition to scattering amplitudes, a whole compendium of inclusive observables exists where the time-ordering is relaxed. These include expectation values of electromagnetic or gravitational radiation fields as well as out-of-time-order amplitudes. We explain how to calculate them in two ways: by relating them to amplitudes and products of amplitudes, and by using a generalization of the LSZ reduction formula. As an application, we discuss one-loop master integrals contributing to gravitational radiation in the post-Minkowski expansion, emphasizing the role of classical cut contributions and highlighting the different infrared physics of in-in observables.
Keywords
Cite
@article{arxiv.2308.02125,
title = {What can be measured asymptotically?},
author = {Simon Caron-Huot and Mathieu Giroux and Holmfridur S. Hannesdottir and Sebastian Mizera},
journal= {arXiv preprint arXiv:2308.02125},
year = {2023}
}
Comments
67 pages, typos corrected