We present a generic framework to compute the one-point statistics of cosmological perturbations, when coarse-grained at an arbitrary scale $R$, in the presence of quantum diffusion. Making use of the stochastic-$\delta N$ formalism, we show how it can be related to the statistics of the amount of expansion realised until the scale $R$ crosses out the Hubble radius. This leads us to explicit...

Primordial black holes can be seeded by perturbations from cosmic inflation. In the literature, these perturbations are often computed in linear order so that their statistics are Gaussian. However, non-Gaussianities can be important for the rare events of black hole formation. The leading non-Gaussianities can be computed with the non-linear formalism of stochastic inflation, which predicts...

If inflation gives rise to large enough curvature perturbations, these will generate large overdensities in the primordial plasma, which may eventually collapse to form primordial black holes when inflation is over.

Therefore, primordial black holes typically arise in inflationary scenarios where the backreaction of large amplitude fluctuations significantly modify the large-scale dynamics of...

A class of inflationary scenarios for primordial black hole (PBH) formation include a small barrier in the slope of the potential. There, the inflaton slows down, generating an enhancement of primordial perturbations. Moreoever, the background solution overcomes the barrier at a very low speed, and large backward quantum fluctuations can prevent certain regions from overshooting the barrier....

If gauge fields are coupled to an axion field during inflation they can lead to unique observational signatures, such as primordial black holes and chiral gravitational waves. However, this system often shows strong backreaction effects, invalidating the standard perturbation theory approach. In this talk, I present the first nonlinear lattice simulation of an axion-U(1) system during...

Primordial black holes (PBHs) may form from large density fluctuations in the early universe. These fluctuations are rare, and so lie in the tail of the probability distribution function. Non-Gaussianity may enhance this tail, and will have a significant impact on PBH formation. The typical perturbative treatment of non-Gaussianity is insufficient for strong deviations from Gaussianity in the...

The primordial black hole (PBH), a hypothetical rare object, is one of the candidates for dark matter. This is made by the gravitational collapse of the region of large curvature perturbation. Though one often adopts the perturbation theory for the growth of the fluctuation, it may fail in the case of large perturbation associated with PBHs. This problem is resolved by the non-perturbative...

Coupling the inflaton field to light degrees of freedom can lead to the former dissipating its energy into a thermal bath. The temperature fluctuations of this bath act as a source for inflaton perturbations. This can potentially lead to an enhancement of the primordial power spectrum $\mathcal{P}_\mathcal{R}$ and the subsequent increased production of primordial black holes (PBHs). We propose...

Primordial Black Holes (PBHs) have recently attracted ample attention as they may explain some of the LIGO/Virgo/KAGRA observations and significantly contribute to the dark matter in our universe. The standard formation scenario assumes PBHs form out of the collapse of large radiation over-densities in the early universe.

We present the computation of PBHs mass fraction in the presence of...

It is generally thought that the supermassive black holes (SMBH) of mass $M \sim 10^{8}-10^{10} M_\odot$ ubiquitous in galactic nuclei grew from initially low mass seeds through the processes of accretion and mergers. Eddington-limited growth, however, is insufficient to explain the surplus of SMBH observed at high redshift $z \sim 6$, when the age of the universe was less than 1 Gyr. An...

I review the observational evidence for primordial black holes (PBHs) from a variety of lensing, dynamical, accretion and gravitational-wave effects. This is a shift from the usual emphasis on PBH constraints. Microlensing observations of stars and quasars suggest that PBHs of around 1 M⊙ could provide most of the dark matter in galactic halos and intergalactic space, especially if they have...

We will discuss constraints on the abundance of primordial black holes of masses around 10^20 g that may result from their cature by main sequence stars in dwarf galaxies, with subsequent destruction of the infected stars. We show that capture of PBH at the stage of star formation is efficient and may significantly affect the star population in some of the observed dwarf galaxies -- those...

Gravitational waves can probe the existence of planetary-mass primordial black holes. During their inspirals, these systems will emit gravitational-wave radiation that can be simply described as coming from quasi-Newtonian orbits. Considering a mass range of 10-7 to 10-2 solar masses, we show that gravitational-wave signals from these systems could be quasi-monochromatic and quasi-infinite,...

Primordial Black Holes (PBHs) can form binaries very efficiently in the early Universe, some of which could be observed merging at low redshift. Searching for such mergers, current Gravitational Wave (GW) observations constrain Solar-mass PBHs to make up less than around one thousandth of the Dark Matter (DM) in our Universe. Such a sub-dominant PBH population is therefore likely to be...

We explore the possibility to detect dark matter (DM) in the form of a new weakly interacting massive particle (WIMP) from its interaction in the dense environment around a primordial black hole (PBH). We constrain the abundance of PBHs from the gamma-ray flux expected by the annihilation of WIMPs gravitationally bound to PBHs. We derive analytically the DM profile around the PBH, forming a...

Primordial black hole is a dark matter candidate in a variety of models of physics beyond the standard model, including supersymmetry and models with asymmetric dark matter. I will discuss the formation of black holes in such scenarios, as well as the effects of predicted PBHs on astrophysics and cosmology.

Primordial black holes might have existed in the early universe and, via their evaporation mechanism (completed before Big Bang Nucleosynthesis), they might have released stable particles beyond the Standard Model. We review the possibility that such particles might contribute to dark matter or dark radiation.

The evaporation of primordial black holes (PBH) with masses ranging from $\sim 10^{-1}$ to $10^9$ g could have generated the whole observed dark matter (DM) relic density. It is typically assumed that after being produced, its abundance freezes and remains constant. However, thermalization and number-changing processes in the dark sector can have a strong impact, in particular enhancing the DM...

Hawking evaporation of black holes is expected to copiously produce all kinds of particles, regardless of their charges. In this talk, I will discuss how Hawking evaporation provides an efficient way of creating dark matter by way of gravity only. I will then explore the interplay between Primordial Black Hole production and interacting dark matter and their potential incompatibilities....

Inflationary models predicting a scale-dependent large amplification of the density perturbations have recently attracted a lot of attention because the amplified perturbations can seed a sizable amount of primordial black holes (PBHs) and stochastic background of gravitational waves (GWs). While the power spectra in these models are computed based on the linear equation of motion, it is not...

With the prospect of future detection of gravitational waves in the next decade and the growing interest in the cosmology of primordial black holes, it is high time to study the dynamics of relevant models of inflation in depth. Typically the models of inflation that can lead to large spectrum of induced gravitational waves and abundant primordial black holes required to reach a large...

I will discuss the possibility of producing a significant fraction of dark matter in the form of primordial black holes (PBHs) in the context of the pre-big bang scenario. To this purpose, we consider the enhancement of curvature perturbations possibly induced by a variation of the sound-speed parameter c_s that emerges naturally due to higher-order string corrections. We describe the...

We examined the production of large curvature perturbations that may lead to PBH formation in the early universe, in particular during preheating. At this stage, large non-linear dynamics lead to the exponential amplification of field perturbations that can ultimately collapse into a black hole or form semi-stable configurations such as oscillons (DM candiate). The details of this phenomenon...

Primordial black holes (PBHs) within the mass range $10^{17} - 10^{22}$ g are a favorable candidate for describing the all of the dark matter content. Towards the lower end of this mass range, the Hawking temperature, $T_{\rm H}$, of these PBHs is $T_{\rm H} \geq 100$ keV, allowing for the creation of electron -- positron pairs; thus making their Hawking radiation a useful constraint for most...

Hawking's calculation of particle production by a black hole is based on the semi-classical limit of a fixed metric. This approximation may break down after a finite time as a black hole evolves due to back-reaction. Therefore, I shall argue that two far-reaching questions remain to be answered:

(1) How long is the semi-classical description valid?

(2) What happens after a potential...

We explore the quantum nature of black holes by introducing an effective framework that takes into account deviations from the classical results. The approach is based on introducing quantum corrections to the classical Schwarzschild geometry in a way that is consistent with the physical scales of the black hole and its classical symmetries. This is achieved by organizing the quantum...

We use the evaporation of Primordial Black Holes as a laboratory to investigate Physics beyond the Standard Model of particles and to probe the structure of black holes.

We show that PBHs develop non-negligible spins through Hawking's emission of many axion-like particles yielding a unique probe of the total number of light scalars in the fundamental theory, independent of how weakly they...

We investigate the impact of stochastic quantum noise due to trans--Planckian effects on the primordial power spectrum for gravity waves during inflation. Given an energy scale Lambda, expected to be close to the Planck scale m_Pl and larger than the Hubble scale H, this noise is described in terms of a source term in the evolution equation for comoving modes k which changes its amplitude...

I will describe superradiant particle production in the context of primordial black holes, discussing its cosmological and astrophysical relevance. In particular, I will focus on the superradiant production of axion-like particles and other exotic bosonic particles that they may account for (a fraction of) dark matter. I will discuss particle production by primordial black holes in the...

Even a small population of primordial black holes with masses above a solar mass could profoundly impact the properties of the intergalactic medium. In this talk, I will show that future observations of the 21cm transition in neutral hydrogen during the cosmic dawn will likely provide one of the most stringent tests of solar mass primordial black holes.

I will present how we can use high-energy astrophysics at multiple wavelengths to constrain PBH DM. First, I will show how old data from INTEGRAL/SPI in the MeV band can be exploited to set the strongest bounds on evaporating PBH. I will also review how we can use GeV to TeV observation to probe PBHs, even if not providing very competitive results. Finally, I will move towards stellar-mass...

Light Dark Matter has recently gained a lot of attention. Generally, direct detection of sub-GeV Dark Matter is challenging since it induces low recoil energies. The problem is solved by considering light Dark Matter with considerable kinetic energies. In this talk, we point out that Primordial Black Hole evaporation is a source of boosted light dark Matter with energies of tens to hundreds of...

Formed in the earliest second of the universe, a galactic halo population of Primordial black holes (PBH) are a simple solution to the dark matter (DM) problem. A halo population of PBHs in the Milky Way may be detected on Earth using small-scale gravitational lensing, or ‘microlensing’.Several decades of microlensing research have gone into constraining the potential range of PBHs and their...

Primordial black holes (PBHs) are of great interest cosmologically: they a promising dark matter candidate, and provide plausible explanations for a number of observations, perhaps most noticeably the observations of gravitational waves from merging black holes. Even if they are never detected, this fact can be used to place unique constraints on the small-scale primordial power spectrum. With...

Primordial Black Holes (PBHs) are interesting compact objects which might have formed due to the gravitational collapse of large density fluctuations in the early universe, which can be generated by quantum fluctuations during inflation. Since PBHs form from rare and non-linear over-densities, their abundance is highly sensitive to the non-Gaussian tail of the primordial probability...

The observation of an evaporating black hole would provide definitive information on the elementary particles present in nature. In particular, it could discover or exclude particles beyond those present in the standard model of particle physics. We consider a wide range of motivated scenarios beyond the standard model and identify those which would be best probed in the event of an...

Primordial black holes are one of the most well-motivated dark matter candidates and it is important to devise new search strategies for them. Low-mass PBHs (masses between ∼ $10^{15}$ g to $10^{18}$ g) can be detected via their Hawking radiation. Evaporating PBHs inject energy into the intergalactic medium (IGM), which can significantly alter the thermal and ionization history of the...

The Standard Model, extended with three right-handed (RH) neutrinos, is the simplest model that can explain light neutrino masses, the baryon asymmetry of the Universe, and dark matter (DM). Models in which RH neutrinos are light are generally easier to test in experiments. In this work, we show that even if the RH neutrinos are super-heavy (Mi=1,2,3 > 10^9 GeV)—close to the Grand Unification...

Ultra-low mass primordial black holes (PBH) which may briefly dominate the energy density of the universe but completely evaporate before the big bang nucleosynthesis (BBN), may lead to interesting observable signatures. We propose a novel test of this scenario by detecting its characteristic doubly peaked gravitational wave (GW) spectrum in future GW observatories. Here the first-order...

Primordial black holes (PBH) can account for a wide variety of cosmic conundra, among which the origin of primordial magnetic fields. In this talk, we consider supermassive PBHs furnished with a disk due to the vortexlike motion of the primordial plasma around them at the epoch of their formation, proposing at the end a novel natural ab initio mechanism for the generation of a battery induced...

PBHs whose masses are in $\sim[10^{-15}M_\odot,10^{-11}M_{\odot}]$ have been extensively studied as a candidate for the whole DM. One of the promising probes to test such a PBH-DM scenario is scalar-induced stochastic GWs accompanied by enhanced primordial fluctuations to form the PBHs with frequency peaked in the mHz band being targeted by the LISA mission.

In order to utilize the stochastic...

In my talk, I will present recent work on the formation of primordial black hole dark matter and the resultant gravitational wave signal, drawing from recent results of (arXiv 2303:xxxxx, MIT-CTP/5525, with co-authors W. Qin, S. Balaji, D.I. Kaiser, and E. McDonough) and building on our previous results as published in (Phys. Rev.D 106, 063535 (2022), arXiv:2205.04471). In our work, we...

We show that primordial near-extremal charged black holes with a wide range of masses from the Planck scale to around 10^9 grams could be cosmologically stable and provide a viable explanation for dark matter. The near-extremal charged black holes can carry either the Standard Model magnetic charges or other dark gauge charges. Several observational methods including the merger events of...

We consider a cosmological scenario in which the very early Universe experienced a transient epoch of matter domination due to the formation of a large population of primordial black holes (PBHs) with masses $M \leq 10^9~{\rm g}$, that evaporate before Big Bang nucleosynthesis. In this context, Hawking radiation would be a non-thermal mechanism to produce a cosmic background of axion-like...

The origin of our universe's cosmological magnetic fields remains a mystery. In this study, we consider whether these magnetic fields could have been generated in the early universe by a population of charged, spinning primordial black holes. To this end, we calculate the strength and correlation length of the magnetic fields generated by this population, and describe their evolution up to the...

Among mechanisms for generating the baryon asymmetry of the universe, leptogenesis is attractive since it simultaneously explains the small neutrino masses via the seesaw mechanism. Experiments offer some valuable constraints, but the parameter space of even minimal leptogenesis models are high-dimensional and difficult to probe directly. However considering a simple and well studied...