Analytic Properties of Infrared-Finite Amplitudes in Theories with Long-Range Forces

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Auteur principal: Lippstreu, Luke
Format: Preprint
Publié: 2025
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author Lippstreu, Luke
author_facet Lippstreu, Luke
contents Infrared divergences obscure important analytic properties of scattering amplitudes, indicating gaps in our understanding of unitarity, causality, and crossing symmetry in theories with long-range forces. Using the exactly solvable model of a charged scalar particle in a fixed Coulomb background, we demonstrate that novel analytic properties arise and can be systematically studied when long-range interactions are properly incorporated. We first canonically quantize a scalar particle in a Coulomb potential, confirming that basic conditions for unitarity and causality hold. We then examine the necessary modifications to the LSZ reduction formula, the general optical theorem, and the treatment of the disconnected components of scattering amplitudes. Next, we show that the Coulomb phase divergence is analytically related to real radiative divergences via crossing symmetry, implying that a well-defined treatment of the Coulomb phase divergence provides constraints on the real radiative divergence. In contrast to the Faddeev-Kulish approach, we propose that an effective way to eliminate infrared divergences and study these analytic properties is to fully solve the quantum theory associated with the asymptotic Hamiltonian.
format Preprint
id arxiv_https___arxiv_org_abs_2505_04702
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Analytic Properties of Infrared-Finite Amplitudes in Theories with Long-Range Forces
Lippstreu, Luke
High Energy Physics - Theory
Infrared divergences obscure important analytic properties of scattering amplitudes, indicating gaps in our understanding of unitarity, causality, and crossing symmetry in theories with long-range forces. Using the exactly solvable model of a charged scalar particle in a fixed Coulomb background, we demonstrate that novel analytic properties arise and can be systematically studied when long-range interactions are properly incorporated. We first canonically quantize a scalar particle in a Coulomb potential, confirming that basic conditions for unitarity and causality hold. We then examine the necessary modifications to the LSZ reduction formula, the general optical theorem, and the treatment of the disconnected components of scattering amplitudes. Next, we show that the Coulomb phase divergence is analytically related to real radiative divergences via crossing symmetry, implying that a well-defined treatment of the Coulomb phase divergence provides constraints on the real radiative divergence. In contrast to the Faddeev-Kulish approach, we propose that an effective way to eliminate infrared divergences and study these analytic properties is to fully solve the quantum theory associated with the asymptotic Hamiltonian.
title Analytic Properties of Infrared-Finite Amplitudes in Theories with Long-Range Forces
topic High Energy Physics - Theory
url https://arxiv.org/abs/2505.04702