UBC Theses and Dissertations
Primordial galactic magnetic fields from the QCD phase transition Forbes, Michael McNeil
In this thesis I describe in detail a mechanism which we proposed to generate large-scale primordial magnetic fields with correlation lengths of 100 kpc today. Domain walls with QCD scale internal structure form, coalesce and attain Hubble scale correlations. These domain walls subsequently align nucleon spins. Due to strong CP violation, nucleons in these walls have anomalous electric and magnetic dipole moments and the walls are ferromagnetic. This induces electromagnetic fields with Hubble size correlations. The same CP violation also induces a maximal helicity (Chern-Simons) correlated through the Hubble volume which may support an "inverse cascade" allowing the initial correlations to grow to 100 kpc today. Details of the physics and estimation methods are presented as well as necessary background and a discussion of the numerical methods used to obtain the classical domain wall solutions. In particular, a nice method for estimating properties of flat domain walls is presented. In addition, possible flaws with the argument are examined and other applications of QCD domain walls to astrophysical problems are discussed.