Chiral charge dynamics in Abelian gauge theories at finite temperature

by Adrien Florio (EPFL - Ecole Polytechnique Federale Lausanne (CH))

Wednesday 5 Jun 2019, 11:30 → 12:30 Europe/Zurich

4/2-011 - TH common room (CERN)

Despite an absence topologically distinct sectors, Abelian fields have a surprisingly rich vacuum dynamics, partly because of the chiral anomaly.   In  this  talk,  I will  present results  obtained  from  real-time  classical lattice simulations  of  a U(1) gauge field in the presence of a chiral chemical potential. Such simulations account for short distance fluctuations, contrary to effective descriptions such as Magneto-Hydrodynamics (MHD).  This system, with non-zero chiral chemical potential, is unstable and relaxes through the production of long-range helical magnetic fields. In particular, I will discuss the regime of self-similar decay associated with the known process of inverse magnetic cascade.  Another effect of interest is the reaction of the system to a background magnetic field. Such a background acts as a vacuum reservoir and leads to an exponential decay of the chemical potential. The associated chiral decay rate is related to the diffusion of the Abelian Chern-Simons number in a magnetic background, in the absence of chemical potential. The rate obtained from the simulations is an order of magnitude larger than the one predicted by MHD. If this result is shown to be robust under quantum corrections such as Hard Thermal Loops, it will call for a revision of the implications of fermion number and chiral number non-conservation in Abelian theory at finite temperature.