Hunt for Light Primordial Black Hole Dark Matter with Ultra-High-Frequency Gravitational Waves

Abstract

Light primordial black holes may comprise a dominant fraction of the dark matter in our Universe. This paper critically assesses whether planned and future gravitational wave detectors in the ultra-high-frequency band could constrain the fraction of dark matter composed of sub-solar primordial black holes. Adopting the state-of-the-art description of primordial black hole merger rates, we compare various signals with currently operating and planned detectors. As already noted in the literature, our findings confirm that detecting individual primordial black hole mergers with currently existing and operating proposals remains difficult. Current proposals involving gravitational wave to electromagnetic wave conversion in a static magnetic field and microwave cavities feature a technology gap with respect to the loudest gravitational wave signals from primordial black holes of various orders of magnitude. However, we point out that one recent proposal involving resonant LC circuits represents the best option in terms of individual merger detection prospects in the range (1 ÷ 100) MHz. In the same frequency range, we note that alternative setups involving resonant cavities, whose concept is currently under development, might represent a promising technology to detect individual merger events. We also show that a detection of the stochastic gravitational wave background produced by unresolved binaries is possible only if the theoretical sensitivity of the proposed Gaussian beam detector is achieved. Such a detector, whose feasibility is subject to various caveats, may be able to rule-out some scenarios for asteroidal mass primordial black hole dark matter. We conclude that pursuing dedicated studies and developments of gravitational wave detectors in the ultra-high-frequency band remains motivated and may lead to novel probes on the existence of light primordial black holes.

Doubly peaked induced stochastic gravitational wave background : Testing baryogenesis from primordial black holes

“…Our analysis paves the way for BSM model building to realize viable scenarios for such high-scale baryogenesis mechanisms in reach of upcoming experiments, including GUT-scale, SUSY, and heavy right-handed neutrino-based baryogenesis mechanisms. We are limiting ourselves to PBHs with mass greater than 10 2 g. With the advent of ultra-high frequency, gravitational wave detection techniques [139,140] even lower mass PBHs will be relevant to explore the ISGWB above kHz frequency range. We plan to address additional interesting possibilities, such as going beyond the initial Poisson distribution of PBHs and incorporating the effects of PBH clustering or non-Gaussian scalar perturbations in future publications.…”

Constraints on PBH as dark matter from observations: a review

“…A good benchmark is therefore the Innermost Stable Circular Orbit (ISCO), the last stable orbit before the merger. For a binary with masses M 1 and M 2 , the frequency of the GWs from the ISCO is [123]:…”

“…The GWs will have an amplitude, which is related to the characteristic strain h c . For a typical merger of an equal mass m PBH binary at a distance d l , h c is approximately [123]:…”

“…An estimation of the sensitivity band for current and future observatories is showcased in figure 3, from [123]. I must repeat their warning that the figure assumes the observation time is only set by the frequency evolution of the inspirals, when time resolution is rather important factor (for more details see [123]), but the figure is very illustrative nonetheless.…”

“…10 -4 10 -2 10 0 10 2 10 4 10 6 10 8 10 10 10 12 10 14 10 16 10 18 10 20 10 -32 projections for the GW emission for small PBHs. Taken from [123]. Solid (dashed) lines indicate the h c spanned by an inspiralling binary with component masses 10 −16 < m PBH < 10 −6 M for f PBH = 1 ( f PBH = 0.1).…”