Black hole production in tachyonic preheating

Abstract

We present fully non-linear simulations of a self-interacting scalar field in the early universeundergoing tachyonic preheating. We find that density perturbations on subhorizon scaleswhich are amplified by tachyonic instability maintain long range correlations evenduring the succeeding parametric resonance, in contrast to the predictions from thestandard models of preheating dominated by parametric resonance. As a resultthe final spectrum exhibits memory and is not universal in shape. We find thatthroughout the subsequent era of parametric resonance the equation of state of theuniverse is almost dust-like; hence the Jeans wavelength is much smaller than thehorizon scale. If our 2D simulations are accurate reflections of the situation in 3D,then there are wide regions of parameter space ruled out by overproduction ofblack holes. It is likely however that realistic parameter values, consistent withCOBE/WMAP normalization, are safely outside this black hole overproduction region.