2025/11/20 by Stavros Christodoulou, Nicolaos Toumbas, Christodoulou, Stavros +1
Physics and Astronomy · #Amplitude #Cold Atom Physics and Bose-Einstein Condensates #High-Energy Particle Collisions Research #Infrared #Perturbation theory (quantum mechanics) #Photon #Quantum Chromodynamics and Particle Interactions #Radiation #Radiative transfer #Scattering #Soft photon #hep-th
paper · pdf · doi:10.1140/epjc/s10052-026-16078-0
published in The European Physical Journal C 86(7) (Springer Science+Business Media)
openalex publication_date 2026/07/18 · openalex created_date 2026/07/19 · openalex updated_date 2026/08/05
Abstract We study soft photon emission during scattering of Faddeev–Kulish charged states in QED at leading order in perturbation theory. The charged asymptotic particles are accompanied by clouds of an infinite number of soft photons of energy less than a characteristic infrared scale Ed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>E</mml:mi> <mml:mi>d</mml:mi> </mml:msub> </mml:math> . When the corresponding “dressing” functions are suitably corrected to subleading order in the soft momentum expansion, as advocated in recent work by Choi and Akhoury, we show explicitly that the emission of additional radiative soft photons with energy less than Ed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>E</mml:mi> <mml:mi>d</mml:mi> </mml:msub> </mml:math> is completely suppressed. Moreover, the dressing renders the elastic amplitudes infrared-finite, order by order in perturbation theory, regulating the infrared divergences due to virtual soft photons at the energy scale Ed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>E</mml:mi> <mml:mi>d</mml:mi> </mml:msub> </mml:math> . Therefore, the characteristic energy scale of the soft photons in the clouds provides an effective infrared cutoff, allowing for the formulation of an infrared finite S-matrix.