Complex Scalar Field Reheating and Primordial Black Hole production

Abstract

We study perturbations of a complex scalar field during reheating with no self-interaction in the regime μ ≫ H, when the scalar field has a fast oscillatory behaviour (close to a pressure-less fluid). We focus on the precise determination of the instability scale and find it differs from that associated to a real scalar field. We further look at the probability that unstable fluctuations form Primordial Black Holes (PBHs) obtaining a significant production of tiny PBHs which quickly evaporate and may subsequently leave a population of Planck-mass relics. We finally impose restrictions on the duration and energy scale of the fast oscillations period by considering that such relics constitute, at most, the totality of dark matter in the Universe.

New mechanism for primordial black hole formation during reheating

“…These objects are produced more effectively in a free-field dominated universe than in the radiation era, but require larger overdensities than those allowed to collapse in a matter-dominated universe (as assumed previously during reheating, e.g., Refs. [32][33][34][35]). Considering an attractive self-interaction, the probability of PBH formation can saturate the sphericity and rotation conditions that constrain the PBH production in the matter-dominated scenario.…”

PBH Formation from Spherically Symmetric Hydrodynamical Perturbations: A Review

“…Thus, the study of abundances, where the Universe is matter-dominated for a finite time, differs greatly from the case of radiation. Some works have considered this scenario with scalar field types [201][202][203][204][205][206], specifically taking into account the oscillatory behaviour of the scalar field during the reheating. Recently, in [207], simulations were performed in full GR using scalar fields to modulate the perturbation and the expanding dust background of the Universe, showing that the PBH mass grows beyond the self-similar limit M PBH ∝ H −1 , at least initially.…”

PBH formation from spherically symmetric hydrodynamical perturbations: a review

“…Thus a study of abundances, where the Universe is matter-dominated for a finite time, differs a lot from the case of radiation. Some works have considered this scenario with scalar fields type [198][199][200][201][202][203], specially taking into account the oscillatory behavior of scalar field during the reheating. Recently in [204] were performed simulations in full GR using scalar fields to modulate the perturbation and the expanding dust background of the Universe, showing that the PBH mass grows beyond the self-similar limit M PBH ∝ H −1 , at least initially.…”