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...
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...
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...
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...
The gravitational Faraday effect is the rotation of the polarization plane of electromagnetic waves when they propagate in a space-time that is not invariant under rotations (e.g. Kerr black holes)
The idea is to use this effect to constrain the spin of primordial black holes through CMB polarisation data.
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.
Primordial black holes (PBH) can account for a wide variety of cosmic conundra, in particular for a part or the totality of dark matter. Very interestingly, a gas of Poisson distributed PBHs can induce at second order in cosmological perturbation theory a stochastic gravitational-wave (GW) background, acting as a novel method to extract constraints on cosmological models and gravitational...
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) 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...
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...
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...
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.
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...
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...
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...
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...
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...
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...
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 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...
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...
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...
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...
Observations of supermassive black holes (SMBHs) with masses exceeding 10^9 solar masses as early as z = 7 pose a significant challenge for contemporary theories of black hole formation and evolution. The canonical model of formation from stellar remnants does not produce sufficiently massive black holes by orders of magnitude in the desired timescales. The first part of this project aims to...
