https://doi.org/10.1140/epjc/s10052-018-6088-2
Regular Article - Theoretical Physics
Infrared divergences and quantum coherence
1
Instituto de Física Teórica UAM-CSIC, Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid, Spain
2
Arnold Sommerfeld Center, Ludwig-Maximilians-Universität, Theresienstraße 37, 80333, Munich, Germany
3
Max-Planck-Institut für Physik, Föhringer Ring 6, 80805, Munich, Germany
* e-mail: sebastian.zell@campus.lmu.de
Received:
16
July
2018
Accepted:
19
July
2018
Published online:
31
July
2018
In theories with long-range forces like QED or perturbative gravity, only rates that include emitted soft radiation are non-vanishing. Independently of detector resolution, finite observables can only be obtained after integrating over the IR-component of this radiation. This integration can lead to some loss of quantum coherence. In this note, however, we argue that it should in general not lead to full decoherence. Based on unitarity, we suggest a way to define non-vanishing off-diagonal pieces of the IR-finite density matrix. For this IR-finite density matrix, we estimate the dependence of the loss of quantum coherence, i.e. of its purity, on the scattering kinematics.
© The Author(s), 2018
