SMuK 2023 – scientific programme
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MP: Fachverband Theoretische und Mathematische Grundlagen der Physik
MP 11: Quantum Field Theory III (QED and Particle Detection)
MP 11.3: Talk
Thursday, March 23, 2023, 16:40–17:00, ZEU/0250
Pair production spectrum in a space-time dependent field from worldline instantons — •Gianluca Degli Esposti1 and Greger Torgrimsson2 — 1Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstraße 400, 01328 Dresden, Germany — 2Department of Physics, Umeå University, SE-901 87 Umeå, Sweden
The Worldline Formalism has proven to be an efficient tool for the computation of scattering amplitudes in a number of interesting cases. In the context of Strong-Field QED, it provides a useful representation of the full propagator in a background electromagnetic field, and in the present work, we use such representation in the LSZ reduction formula to compute the pair production spectrum in a space-time dependent electric field.
Unlike the closed-loop method that provides the total integrated probability from the effective action using unitarity, we work with the LSZ on the amplitude level, which allows us to obtain the spectrum. We use the saddle-point approximation to obtain a semiclassical result.
The instantons are the saddle points of the path integral. They represent tunneling near the turning point and free real particles asymptotically. We find such instantons numerically by solving the Lorentz force equation.