What can be measured asymptotically?

Caron-Huot, Simon; Giroux, Mathieu; Hannesdottir, Holmfridur S.; Mizera, Sebastian

doi:10.1007/jhep01(2024)139

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What can be measured asymptotically?

Caron-Huot, Simon·Giroux, Mathieu·Hannesdottir, Holmfridur S.·Mizera, Sebastian

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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.

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Caron-Huot, Simon, Giroux, Mathieu, Hannesdottir, Holmfridur S., Mizera, Sebastian. 2024-01-24. What can be measured asymptotically?. https://doi.org/10.1007/jhep01(2024)139

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