Radiation reaction in strong field QED

We derive radiation reaction from QED in a strong background field. We identify, in general, the diagrams and processes contributing to recoil effects in the average momentum of a scattered electron, using perturbation theory in the Furry picture: we work to lowest nontrivial order in the electromagnetic coupling alpha. For the explicit example of scattering in a plane wave background, we compare QED with classical electrodynamics in the limit h-bar goes to zero, finding agreement with the Lorentz-Abraham-Dirac and Landau-Lifshitz equations, and with Larmor's formula. The first quantum corrections are also presented.Comment: Version2: 7 pages, 2 figures. Discussion of related results and applications extended, references added. Matches version to appear in Phys.Lett.

Radiation reaction from QED: lightfront perturbation theory in a plane wave background

We derive dynamical, real time radiation reaction effects from lightfront QED. Combining the Hamiltonian formalism with a plane wave background field, the calculation is performed in the Furry picture for which the background is treated exactly while interactions between quantum fields are treated in perturbation theory as normal. We work to a fixed order in perturbation theory, but no other approximation is made. The literature contains many proposals for the correct classical equation describing a radiating particle; we take the classical limit of our results and identify which equations are consistent with QED.Comment: 33 pages, 5 pdf figures. Version 3: corrected typographical mistakes and presentation issues in equations 4.10--4.14 and accompanying discussion. Results and conclusions unaffected and unchange

Corrections to Laser Electron Thomson Scattering

We discuss classical and quantum corrections to Thomson scattering between an electron and a laser. For radiation reaction, nonlinear, and quantum effects we identify characteristic dimensionless parameters in terms of which we determine the leading order correction terms.Comment: 5 pages, 1 figure; updated version of contribution to 2012 Annual Report, Central Laser Facility (CLF), Rutherford-Appleton Laboratory, U

Physics of adiabatic particle number in the Schwinger effect

The production of electron-positron pairs from light is a famous prediction of quantum electrodynamics. Yet it is often emphasised that the number of produced pairs has no physical meaning until the driving electromagnetic fields are switched off, as otherwise its definition is basis-dependent. The common adiabatic definition, in particular, can predict the `creation' of a number of pairs orders of magnitude larger than the final yield. We show here, by clarifying exactly what is being counted, that the adiabatic number of pairs has an unambiguous and physical interpretation. As a result, and perhaps contrary to expectation, the large numbers of pairs seen at non-asymptotic times become, in principle, physically accessible.Comment: V2: matches published version. More pheno added. Message unchanged. 11 page

Stability, creation and annihilation of charges in gauge theories

We show how to construct physical, minimal energy states for systems of static and moving charges. These states are manifestly gauge invariant. For charge-anticharge systems we also construct states in which the gauge fields are restricted to a finite volume around the location of the matter fields. Although this is an excited state, it is not singular, unlike all previous finite volume descriptions. We use our states to model the processes of pair creation and annihilation.Comment: Six EPS figures. Version 2: minor typos correcte