A scattering amplitudes approach to hard thermal loops

Abstract

Inspired by recent progress on classical limits of scattering amplitudes, we show that hard thermal loops can be obtained from classical limits of off-shell currents. The classicality of hard thermal loops is made manifest by associating classical wavenumbers to soft particles. We compute the classical limit of these currents in QED, QCD and gravity. Our proposal does not involve the introduction of ghosts.

13 pages plus references, 3 Figures, v2: references added and minor typos corrected, v3: clarifications and references added, version to be published