The mass shell of strong-field quantum electrodynamics

Abstract

It has long been known that a free electron in an intense plane-wave field has a mass shell that differs from the usual free-electron mass shell, with a form that implies that an intensity-dependent increase in mass occurs. It has been an enticing, but elusive goal to observe this mass shift. Many schemes have been proposed by which a definitive measurement may be made, and some claims of success exist, but these tests are not conclusive. It is shown here that the intense-field mass shell is not the result of a change in mass. Rather, it is a consequence of the potential energy that a charged particle must possess in the presence of a plane-wave field. When the effects of this potential are incorporated in a properly covariant form, the mass shift no longer appears and kinematical relations are conventional. If the plane-wave pulse is sufficiently long to allow the electron to exit the field adiabatically, then there is no alteration at all of the mass shell expression. Other aspects of the role played by the ponderomotive 4-potential are examined. It is also shown that the putative "relativistic mass" of the electron is illusory when confronted with covariance requirements. Both "mass increases" of the electron are thereby discredited by fundamental principles.

References in corpus (4)

• Nonlinear Compton scattering in ultra-short laser pulses
• Partitioning of the linear photon momentum in multiphoton ionization
• The intensity dependent mass shift: existence, universality and detection
• Altered Maxwell equations in the length gauge

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• Narrowband inverse Compton scattering x-ray sources at high laser intensities
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• Generalized Klein-Nishina formula
• Fundamental formulation of light-matter interactions revisited
• Physical restrictions on the choice of electromagnetic gauge and their practical consequences
• Nonlinear QED in an ultrastrong rotating electric field: Signatures of the momentum-dependent effective mass
• Generation of quasi-monoenergetic positron beams in chirped laser fields
• Electrodynamics of the strong-field approximation and deficiencies of the tunneling model
• Fundamental formulation of electrodynamics revisited, and the precision of quantum electrodynamics
• Dual gauge concepts in electrodynamics, and new limitations on gauge invariance
• Ascendancy of potentials over fields in electrodynamics