Magnetic field generation from nonequilibrium phase transitions

Abstract

We study the generation of magnetic fields during the stage of particle production resulting from spinodal instabilities during phase transitions out of equilibrium. The main premise is that long-wavelength instabilities that drive the phase transition lead to strong nonequilibrium charge and current fluctuations which generate electromagnetic fields. We present a formulation based on the nonequilibrium Schwinger-Dyson equations that leads to an exact expression for the spectrum of electromagnetic fields valid for general theories and cosmological backgrounds and whose main ingredient is the transverse photon polarization out of equilibrium. This formulation includes the dissipative effects of the conductivity in the medium. As a prelude to cosmology, we study magnetogenesis in Minkowski spacetime in a theory of N charged scalar fields to lowest order in the gauge coupling and to leading order in the large N within two scenarios of cosmological relevance. The long-wavelength power spectrum for electric and magnetic fields at the end of the phase transition is obtained explicitly. It follows that equipartition between electric and magnetic fields does not hold out of equilibrium. In the case of a transition from a high-temperature phase, the conductivity of the medium severely hinders the generation of magnetic fields; however, the magnetic fields generated are correlated on scales of the order of the domain size, which is much larger than the magnetic diffusion length. The implications of the results to cosmological phase transitions driven by spinodal instabilities are discussed.

Dark matter clustering: A simple renormalization group approach

“…While the potential usefulness of this RG method appears to be clear, and versions of it have been successful in many previous applications [43,44,49,50,51,52,53,54,55,56,57,58,59,69,70], the exact conditions in which it will succeed or fail are not completely understood. However, the presence of an attractive fixed point (or manifold) is clearly a positive feature [49,50].…”

“…These papers should be useful to the reader who is unsatisfied with my presentation, or wants to extend it. During the last several years, [53,54,55,56,57,58,59] have extended and generalized this dynamical renormalization group method to compute the real time evolution of expectation values of quantum fields.…”

Effect of primordial magnetic field on seeds for large scale structure

“…The origin of PMFs has been intensively studied [1,2,3,4,5,6,7,8]. Although it seems unlikely to survive an epoch of inflation, it is conceivable that large-scale magnetic fields and magnetic inhomogeneities could be generated at the end of that era or in subsequent phase transitions [9].…”

Cosmological Consequences of QCD Phase Transition(s) in Early Universe

“…Therefore, strong fluctuations on the pion fields known as DCC, disordered chiral condensates [22], are quite likely through the transition. If chiral phase transition takes place through an out-of-equilibrium process, it would provide a crucial tool to explain the primordial magnetic fields [23]. The origin of the primordial magnetic fields shall be studied by the Square Kilometer Array (SKA) [24].…”