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Analysis

This paper investigates the production of primordial black holes (PBHs) as a dark matter candidate within the framework of Horndeski gravity. It focuses on a specific scenario where the inflationary dynamics is controlled by a cubic Horndeski interaction, leading to an ultra-slow-roll phase. The key finding is that this mechanism can amplify the curvature power spectrum on small scales, potentially generating asteroid-mass PBHs that could account for a significant fraction of dark matter, while also predicting observable gravitational wave signatures. The work is significant because it provides a concrete mechanism for PBH formation within a well-motivated theoretical framework, addressing the dark matter problem and offering testable predictions.
Reference

The mechanism amplifies the curvature power spectrum on small scales without introducing any feature in the potential, leading to the formation of asteroid-mass PBHs.

Analysis

This paper provides a concise review of primordial black hole (PBH) formation mechanisms originating from first-order phase transitions in the early universe. It's valuable for researchers interested in PBHs and early universe cosmology, offering a consolidated overview of various model-dependent and independent mechanisms. The inclusion of model-specific examples aids in understanding the practical implications of these mechanisms.
Reference

The paper reviews the creation mechanism of primordial black holes from first order phase transitions.

Analysis

This paper explores the formation of primordial black holes (PBHs) within a specific theoretical framework (Higgs hybrid metric-Palatini model). It investigates how large density perturbations, originating from inflation, could have led to PBH formation. The study focuses on the curvature power spectrum, mass variance, and mass fraction of PBHs, comparing the results with observational constraints and assessing the potential of PBHs as dark matter candidates. The significance lies in exploring a specific model's predictions for PBH formation and its implications for dark matter.
Reference

The paper finds that PBHs can account for all or a fraction of dark matter, depending on the coupling constant and e-folds number.

Analysis

This paper proposes a novel method to detect primordial black hole (PBH) relics, which are remnants of evaporating PBHs, using induced gravitational waves. The study focuses on PBHs that evaporated before Big Bang nucleosynthesis but left behind remnants that could constitute dark matter. The key idea is that the peak positions and amplitudes of the induced gravitational waves can reveal information about the number density and initial abundance of these relics, potentially detectable by future gravitational wave experiments. This offers a new avenue for probing dark matter and the early universe.
Reference

The peak frequency scales as $f_{ ext {relic }}^{1 / 3}$ where $f_{ ext {relic }}$ is the fraction of the PBH relics in the total DM density.

Analysis

This paper investigates how smoothing the density field (coarse-graining) impacts the predicted mass distribution of primordial black holes (PBHs). Understanding this is crucial because the PBH mass function is sensitive to the details of the initial density fluctuations in the early universe. The study uses a Gaussian window function to smooth the density field, which introduces correlations across different scales. The authors highlight that these correlations significantly influence the predicted PBH abundance, particularly near the maximum of the mass function. This is important for refining PBH formation models and comparing them with observational constraints.
Reference

The authors find that correlated noises result in a mass function of PBHs, whose maximum and its neighbourhood are predominantly determined by the probability that the density contrast exceeds a given threshold at each mass scale.