Primordial magnetic field amplification from turbulent reheating

ESTEBAN CALZETTA; ALEJANDRA KANDUS

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS

IOP PUBLISHING LTD

Lugar: Londres; Año: 2010 vol. 8 p. 7 - 7

1475-7516

We analyze the possibility of primordial magnetic field amplification by a stochasticlarge scale kinematic dynamo during reheating. We consider a charged scalar field minimallycoupled to gravity. During inflation this field is assumed to be in its vacuum state.At the transition to reheating the state of the field changes to a many particle/anti-particlestate. We characterize that state as a fluid flow of zero mean velocity but with a stochasticvelocity field. We compute the scale-dependent Reynolds number Re(k), and the characteristictimes for decay of turbulence, td and pair annihilation ta, finding ta ≪ td. We calculatethe rms value of the kinetic helicity of the flow over a scale L and show that it does not vanish.We use this result to estimate the amplification factor of a seed field from the stochastickinematic dynamo equations. Although this effect is weak, it shows that the evolution of thecosmic magnetic field from reheating to galaxy formation may well be more complex than asdictated by simple flux freezing.