Unitarity and the On-Shell Action of Worldline Quantum Field Theory

Fuente: arXiv
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Autori principali: Haddad, Kays, Jakobsen, Gustav Uhre, Mogull, Gustav, Plefka, Jan
Natura: Preprint
Pubblicazione: 2025
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author Haddad, Kays
Jakobsen, Gustav Uhre
Mogull, Gustav
Plefka, Jan
author_facet Haddad, Kays
Jakobsen, Gustav Uhre
Mogull, Gustav
Plefka, Jan
contents We develop the on-shell action formalism within Worldline Quantum Field Theory (WQFT) to describe scattering of spinning compact bodies in General Relativity in the post-Minkowskian (PM) expansion. The real on-shell action is constructed from vacuum diagrams with causal (retarded) propagators from which scattering observables such as momentum impulse and spin kick follow via Poisson brackets of the initial scattering data. Furthermore, we explore the implications of unitarity at the level of the worldline and show how generalised unitarity techniques can be adapted to WQFT to efficiently compute multi-loop contributions. Our work establishes a concrete link between WQFT and amplitude-based methods, elucidating how unitarity cuts ensure equivalence between the on-shell action derived from either approach. Extending the state-of-the-art, we complete the full on-shell action -- including dissipative terms -- at (formal) 3PM order and up to quartic spin interactions on both massive bodies.
format Preprint
id arxiv_https___arxiv_org_abs_2510_00988
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Unitarity and the On-Shell Action of Worldline Quantum Field Theory
Haddad, Kays
Jakobsen, Gustav Uhre
Mogull, Gustav
Plefka, Jan
High Energy Physics - Theory
General Relativity and Quantum Cosmology
We develop the on-shell action formalism within Worldline Quantum Field Theory (WQFT) to describe scattering of spinning compact bodies in General Relativity in the post-Minkowskian (PM) expansion. The real on-shell action is constructed from vacuum diagrams with causal (retarded) propagators from which scattering observables such as momentum impulse and spin kick follow via Poisson brackets of the initial scattering data. Furthermore, we explore the implications of unitarity at the level of the worldline and show how generalised unitarity techniques can be adapted to WQFT to efficiently compute multi-loop contributions. Our work establishes a concrete link between WQFT and amplitude-based methods, elucidating how unitarity cuts ensure equivalence between the on-shell action derived from either approach. Extending the state-of-the-art, we complete the full on-shell action -- including dissipative terms -- at (formal) 3PM order and up to quartic spin interactions on both massive bodies.
title Unitarity and the On-Shell Action of Worldline Quantum Field Theory
topic High Energy Physics - Theory
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2510.00988