Dressed states from gauge invariance

Abstract

The dressed state formalism enables us to define the infrared finite $S$-matrix for QED. In the formalism, asymptotic charged states are dressed by clouds of photons. The dressed asymptotic states are originally obtained by solving the dynamics of the asymptotic Hamiltonian in the far past or future region. However, there was an argument that the obtained dressed states are not gauge invariant. We resolve the problem by imposing a correct gauge invariant condition. We show that the dressed states can be obtained just by requiring the gauge invariance of asymptotic states. In other words, Gauss's law naturally leads to proper asymptotic states for the infrared finite $S$-matrix. We also discuss the relation between the dressed state formalism and the asymptotic symmetry for QED.

23 pages; v2: minor corrections, refs. added, v3: published version

References in corpus (7)

• Infrared Divergences in QED, Revisited
• Shaving off Black Hole Soft Hair
• Large Gauge Symmetries and Asymptotic States in QED
• CFT representation of interacting bulk gauge fields in AdS
• Asymptotic structure of a massless scalar field and its dual two-form field at spatial infinity
• Soft pion theorem, asymptotic symmetry and new memory effect
• String Memory Effect