Analytic description of primordial black hole formation from scalar field fragmentation

Abstract

Primordial black hole (PBH) formation is a more generic phenomenon than was once thought. The dynamics of a scalar field in inflationary universe can produce PBHs under mild assumptions regarding the scalar potential. In the early universe, light scalar fields develop large expectation values during inflation and subsequently relax to the minimum of the effective potential at a later time. During the relaxation process, an initially homogeneous scalar condensate can fragment into lumps via an instability similar to the gravitational (Jeans) instability, where the scalar self-interactions, rather than gravity, play the leading role. The fragmentation of the scalar field into lumps (e.g. Q-balls or oscillons) creates matter composed of relatively few heavy "particles", whose distribution is subject to significant fluctuations unconstrained by comic microwave background (CMB) observations and unrelated to the large-scale structure. If this matter component comes to temporarily dominate the energy density before the scalar lumps decay, PBHs can be efficiently produced during the temporary matter-dominated era. We develop a general analytic framework for description of PBH formation in this class of models. We highlight the differences between the scalar fragmentation scenario and other commonly considered PBH formation models. Given the existence of the Higgs field and the preponderance of scalar fields within supersymmetric and other models of new physics, PBHs constitute an appealing and plausible candidate for dark matter.

Neutrino and Positron Constraints on Spinning Primordial Black Hole Dark Matter

“…Given this increased scrutiny of PBHs (which started after the direct detection of gravitational waves [30,31] and the subsequent proposal that these BHs are primordial in nature [32][33][34][35]), it is obvious to ask if we have explored all the properties of BHs in our searches for PBHs. Typically, it has been assumed that PBHs have low spins [36][37][38], however, there exist viable cosmological scenarios where PBHs are born with a high spin [39][40][41][42][43][44][45][46]. Angular momentum is a fundamental property of BHs and it is crucial to explore its implications [47][48][49][50].…”

Primordial Black Hole Dark Matter and Ways to Find It

“…The fragmentation process is stochastic and rare sub-horizon scalar lump overdensities could be sufficiently large to collapse into PBHs [21][22][23][24]. In Fig.…”

“…1 we display the resulting PBH massspectrum for several models (A, B, C), along with existing constraints. Intriguingly, scalar fields associated with electroweak-scale supersymmetry can naturally result in the PBH masses for which there are no observational constraints and that can account for all DM [24]. In this formation mechanism perturbations leading to PBHs are not related to inflation.…”

Mass bound for primordial black hole from trans-Planckian censorship conjecture

“…We conclude in the last section. It is worth noting that, the derived PBH mass bounds would not be applicable to other scenarios of PBH production from curvaton [25,26], scalar lumps [27,28], cosmic strings [29,30], domain walls [31,32], primordial bubbles [33], bubble collisions [34,35], and preheating instability [36], to name just a few.…”