arXiv subjects

Antonio Junior Iovino

Publications and source records attributed to Antonio Junior Iovino.

6 recordsLinked to original sources

arXiv2026

The impact of non-Gaussianity when searching for Primordial Black Holes with LISA

LISA can observe cosmological millihertz (mHz) gravitational wave (GW) backgrounds that may offer a decisive test for asteroid-mass primordial black hole (PBH) dark matter (DM). In standard scenarios, failing to detect a scalar-induced gravitational wave (SIGW) background would exclude the last viable window for PBH DM formed through critical collapse. We show that this conclusion becomes much weaker in the presence of astrophysical foregrounds and strongly non-Gaussian primordial density perturbations, by studying how these phenomena affect the link between SIGWs and PBHs, and reevaluate LISA's sensitivity to asteroid-mass PBHs. In addition, we analyse the interplay between PBHs and SIGWs to gain further insights into the nature of primordial non-Gaussianity. We find that uncertainties in $f_{\rm NL}$ can induce substantial uncertainties in the PBH abundance, which ultimately limits LISA's capacity to fully probe the asteroid-mass PBH DM window.

astro-ph.CO↗

arXiv2025

Cosmic Whispers of the Early Universe: Gravitational Waves and Dark Matter from Primordial Black Holes

Various mechanisms have been suggested for the formation of Primordial Black Holes (PBHs), and this thesis focuses on the standard mechanism based on the critical collapse of cosmological fluctuations. The underlying idea is that during inflation, a period of rapid expansion in the early Universe, large cosmological fluctuations could have been generated. After inflation, when the cosmic horizon reached a size comparable to these fluctuations, if the latter were high enough, they could collapse and form a PBH. Beyond the fascinating possibility that these compact objects might make up all or part of the Dark Matter (DM) we observe today, their formation and existence is also associated with the generation of gravitational waves (GWs). These waves could contribute to the merger events observed by the LIGO/Virgo/KAGRA Collaboration (LVK) or account for signals detected by pulsar timing array experiments (PTA). In the first part of this thesis, we investigate the PBH scenario, examining the computation of the abundance beyond the Gaussian paradigm. In the second part, we discuss how PBH formation can produce a stochastic GW background and how observations, related to recent experiments such as LVK and PTA collaborations, can help in distinguishing between different PBH production models. Finally, in the last part, we investigate some aspects of the interplay between black holes and fundamental physics in the early Universe, describing some characteristics and challenges of various PBH production models.

astro-ph.CO↗

arXiv2024

One loop to rule them all: Perturbativity in the presence of ultra slow-roll dynamics

We discuss the issue of perturbativity in single-field inflationary models with a phase of ultra slow-roll (USR) tailor suited to generate an order-one abundance of primordial black holes (PBHs). More in detail, we impose the condition that loop corrections made up of short-wavelength modes enhanced by the USR dynamics do not alter the tree-level power spectrum of curvature perturbations. In our analysis, the USR phase is preceded and followed by two stages of ordinary slow-roll (SR), and we model the resulting SR/USR/SR dynamics using both instantaneous and smooth transitions. Focusing on scales relevant for CMB observations, we find that it is not possible, with these arguments, to rule out the scenario of PBH formation via USR, not even in the limit of instantaneous transition. However, we also find that loop corrections of short modes on the power spectrum of long modes, even though not large enough to violate perturbativity requirements, remain appreciable and, most importantly, are not tamed in realistic realisations of smooth SR/USR/SR transitions. This makes perturbativity a powerful theoretical tool to constrain USR dynamics. We extend the analysis at any scale beyond those relevant for CMB observations. We find that loop corrections of short modes remain within the few percent if compared to the tree-level power spectrum. However, we also find one notable exception of phenomenological relevance: we show that the so-called dip in the power spectrum of curvature perturbation is an artifact of the tree-level computation.

astro-ph.CO↗

arXiv2023

The recent gravitational wave observation by pulsar timing arrays and primordial black holes: the importance of non-gaussianities

We study whether the signal seen by pulsar timing arrays (PTAs) may originate from gravitational waves (GWs) induced by large primordial perturbations. Such perturbations may be accompanied by a sizeable primordial black hole (PBH) abundance. We improve existing analyses and show that PBH overproduction disfavors Gaussian scenarios for scalar-induced GWs at 2σ and single-field inflationary scenarios, accounting for non-Gaussianity, at 3σ as the explanation of the most constraining NANOGrav 15-year data. This tension can be relaxed in models where non-Gaussianites suppress the PBH abundance. On the flip side, the PTA data does not constrain the abundance of PBHs.

astro-ph.CO↗

arXiv2023

Primordial black holes in the curvaton model: possible connections to pulsar timing arrays and dark matter

We revise primordial black holes (PBHs) production in the axion-curvaton model, in light of recent developments in the computation of their abundance accounting for non-gaussianities (NGs) in the curvature perturbation up to all orders. We find that NGs intrinsically generated in such scenarios have a relevant impact on the phenomenology associated to PBHs and, in particular, on the relation between the abundance and the signal of second-order gravitational waves. We show that this model could explain both the totality of dark matter in the asteroid mass range and the tentative signal reported by the NANOGrav and IPTA collaborations in the nano-Hz frequency range. En route, we provide a new, explicit computation of the power spectrum of curvature perturbations going beyond the sudden-decay approximation.

astro-ph.CO↗

arXiv2023

Primordial non-gaussianity up to all orders: theoretical aspects and implications for primordial black hole models

We develop an exact formalism for the computation of the abundance of primordial black holes (PBHs) in the presence of local non-gaussianity (NG) in the curvature perturbation field. For the first time, we include NG going beyond the widely used quadratic and cubic approximations, and consider a completely generic functional form. Adopting threshold statistics of the compaction function, we address the computation of the abundance both for narrow and broad power spectra. While our formulas are generic, we discuss explicit examples of phenomenological relevance considering the physics case of the curvaton field. We carefully assess under which conditions the conventional perturbative approach can be trusted. In the case of a narrow power spectrum, this happens only if the perturbative expansion is pushed beyond the quadratic order (with the optimal order of truncation that depends on the width of the spectrum). Most importantly, we demonstrate that the perturbative approach is intrinsically flawed when considering broad spectra, in which case only the non-perturbative computation captures the correct result. Finally, we describe the phenomenological relevance of our results for the connection between the abundance of PBHs and the stochastic gravitational wave (GW) background related to their formation. As NGs modify the amplitude of perturbations necessary to produce a given PBHs abundance and boost PBHs production at large scales for broad spectra, modelling these effects is crucial to connect the PBH scenario to its signatures at current and future GWs experiments.

astro-ph.CO↗