Ref Arxiv: 2201.02521
DOI: 10.1103/PhysRevD.105.083520
Ref. & Cit.: NASA ADS
Abstract:

The discovery of black-hole-binary mergers through their gravitational wave (GW) emission has reopened the exciting possibility that dark matter is made, at least partly, of primordial black holes (PBHs). However, this scenario is challenged by many observational probes that set bounds on the relative PBH abundance across a broad range of viable PBH masses. Among these bounds, the ones coming from microlensing surveys are particularly severe in the mass range from $\sim 10^{-10}$ to a few M$_{\odot}$. The upper part of this range precisely corresponds to the mass window inside which the formation of PBHs should be boosted due to the QCD phase transition in the early Universe, which makes the microlensing probes particularly important. However, it has been argued that taking into account the inevitable clustering of PBH on small scales can significantly relax or entirely remove these bounds. While the impact of PBH clustering on the GW event rate has been studied in detail, its impact on the microlensing event rate has not yet been fully assessed. In this Letter, we address this issue, and show that clusters arising from PBH formed from Gaussian initial curvature perturbations do not alter the current microlensing constraints, as they are not sufficiently dense nor massive.

Comments: 9 pages, 1 figure. Comments are welcome!

Ref Arxiv: 1812.08795
Ref INSPIRE: 1711119
DOI: 10.1088/1475-7516/2019/02/051
Ref. & Cit.: NASA ADS
2 citations

Ref Arxiv: 1804.06115
Ref INSPIRE: 1668190
DOI: 10.1103/PhysRevLett.123.021301
Ref. & Cit.: NASA ADS
13 citations

DOI: 10.1088/1475-7516/2016/11/032

Ref HAL: hal-00460779_v1
Ref Arxiv: 1002.3278
DOI: 10.1088/1475-7516/2010/04/021
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
32 citations
Abstract:

In the pre-reheating era, following cosmic inflation and preceding radiation domination, the energy density may be dominated by an oscillating massive scalar condensate, such as is the case for quadratic chaotic inflation. We have found in a previous paper that during this period, a wide range of sub-Hubble scale perturbations are subject to a preheating instability, leading to the growth of density perturbations ultimately collapsing to form non-linear structures. We compute here the gravitational wave signal due to these structures in the linear limit and present estimates for emission in the non-linear limit due to various effects: the collapse of halos, the tidal interactions, the evaporation during the conversion of the inflaton condensate into radiation and finally the ensuing turbulent cascades. The gravitational wave signal could be rather large and potentially testable by future detectors.

Ref HAL: hal-00460778_v1
Ref Arxiv: 1002.3039
DOI: 10.1088/1475-7516/2010/09/034
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
40 citations
Abstract:

After cosmic inflation and before the transition to radiation domination, the cosmic energy density may have been dominated during an extended period by an oscillating massive scalar condensate. We show that during this period, sub-Hubble scale perturbations are subject to a metric preheating instability in the narrow resonance regime. We analyze in detail both, quadratic and quartic potentials. The instability leads to the growth of density perturbations which in many cases become non-linear already before the beginning of a radiation dominated Universe. This is particularly the case when requiring a phenomenologically preferred low reheat temperature. These early structures may lead to the emission of gravitational waves and the production of primordial black holes. Furthermore, it is not clear if they could modify the prediction of linear curvature perturbations on very large scales.

Ref HAL: hal-00430281_v1
Ref Arxiv: 0911.1120
DOI: 10.1007/JHEP03(2010)080
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
429 citations
Abstract:

We propose an alternate, calculable mechanism of dark matter genesis,"thermal freeze-in," involving a Feebly Interacting Massive Particle (FIMP)interacting so feebly with the thermal bath that it never attains thermalequilibrium. As with the conventional "thermal freeze-out" productionmechanism, the relic abundance reflects a combination of initial thermaldistributions together with particle masses and couplings that can be measuredin the laboratory or astrophysically. The freeze-in yield is IR dominated bylow temperatures near the FIMP mass and is independent of unknown UV physics,such as the reheat temperature after inflation. Moduli and modulinos of stringtheory compactifications that receive mass from weak-scale supersymmetrybreaking provide implementations of the freeze-in mechanism, as do models thatemploy Dirac neutrino masses or GUT-scale-suppressed interactions. Experimentalsignals of freeze-in and FIMPs can be spectacular, including the production ofnew metastable coloured or charged particles at the LHC as well as thealteration of big bang nucleosynthesis.