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arXiv · 2204.02378

The eikonal operator at arbitrary velocities I: the soft-radiation limit

Paolo Di Vecchia·Carlo Heissenberg·Rodolfo Russo·Gabriele Veneziano
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Abstract

Observables related to the real part of the gravitational eikonal, such as the deflection angle and time delay, have been found so far to have a smooth post-Minkowskian (PM) expansion whose validity extends from the non-relativistic to the most extreme ultra-relativistic (UR) regime, which smoothly connects with massless particle collisions. To describe gravitational radiation, the eikonal phase has to be promoted to a unitary operator for which we motivate a proposal and start discussing properties in the soft-radiation limit. A convergent PM expansion is found to only hold below an UR bound (discussed in the GR literature in the seventies) above which a different expansion is instead needed implying, in general, some non-analyticity in Newton's constant. In this extreme UR regime soft radiative observables receive contributions only from gravitons and are therefore universal. This generalises the pattern discussed in \cite{DiVecchia:2020ymx} beyond the elastic case.

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Paolo Di Vecchia, Carlo Heissenberg, Rodolfo Russo, Gabriele Veneziano. 2022-04-05. The eikonal operator at arbitrary velocities I: the soft-radiation limit. https://arxiv.org/abs/2204.02378

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