Special Particle Theory Seminar: Christopher Verhaaren, University of California, Davis, “Resolving the Weinberg Paradox”

Event time: 
Monday, December 17, 2018 - 4:00pm to 5:00pm
Location: 
Sloane Physics Laboratory (SPL), Room 52 See map
217 Prospect Street
New Haven, CT 06511
Event description: 

Resolving the Weinberg Paradox

Abstract: Long ago, Weinberg showed, from first principles, that the amplitude for a single photon exchange between an electric current and a magnetic current violates Lorentz invariance. The obvious conclusion at the time was that monopoles were not allowed in quantum field theory. Since the discovery of topological monopoles there has thus been a paradox. On the one hand, topological monopoles are constructed in Lorentz invariant quantum field theories, while on the other hand, the low-energy effective theory for such monopoles will reproduce Weinberg’s result. I examine a toy model where both electric and magnetic charges are perturbatively coupled and show how soft-photon resummation for hard scattering exponentiates the Lorentz violating pieces to a phase that is the covariant form of the Aharonov-Bohm phase due to the Dirac string. The squared scattering amplitudes (and hence observables) are Lorentz invariant, and when Dirac charge quantization is imposed the amplitude itself is also Lorentz invariant.

Open to: 
undergraduate