Quantum Theory Seminar
Spontaneous breaking of Lorentz symmetry in QED3
Thursday May 12, 2016 14:15:00 CEST
Thursday May 12, 2016 15:45:00 CEST
Dr. Lukas Janssen (TU Dresden)
Abstract: The phase diagram of quantum electrodynamics in three space-time dimensions as a function of fermion flavor number N exhibits two well-known phases: at large N > Nc1 the system is in a conformal gapless state, while for small N < Nc2 the fermions are expected to develop a dynamical mass due to spontaneous chiral symmetry breaking. Using epsilon expansion near the lower critical dimension of two, in combination with the recent results on the generalization of the F theorem to continuous dimension, we show that Nc1 > Nc2. There is therefore an intermediate range of values of N at which a third phase is stabilized. We demonstrate that this phase is characterized by spontaneous breaking of Lorentz symmetry, in which a composite vector boson field acquires a vacuum expectation value with the fermions and the photon remaining massless.