The probability of large primordial scalar perturbations (leading to primordial black hole formation and the concurrent GW backgrounds) is sensitive to the tail of the PDF of primordial curvature perturbations. We analyse such tails in inflationary models featuring an ultra slow-roll phase, known to enhance both the amplitude and non-Gaussianity of curvature perturbations at small scales. We...
Effective field theories (EFTs) parametrize our ignorance of the underlying UV theory through their Wilson coefficients. However, not all values of these coefficients are consistent with fundamental physical principles. In this paper, we explore the consequences of imposing causal propagation on the comoving curvature perturbation in the EFT of inflation, particularly its impact on the...
Both single- and multi-field models of inflation might lead to enhanced scalar fluctuations on scales much smaller than those seeding the large-scale structure formation. In these scenarios, it is possible that the spike of power at high wavenumber might induce large corrections to the scalar power spectrum, e.g. in the form of loop corrections, potentially endangering the perturbativity of...
Inflationary models with an inflection point potential may produce a significant abundance of primordial black holes. I show that in typical models, inflation is eternal near the inflection point, that is, the volume of the inflating region diverges at late times. The inflating space then has a fractal structure, with eternal inflation taking place inside type II black holes. I discuss the...
Quantum fluctuations during inflation in the very early universe inevitably generate inhomogeneities and anisotropies across all observable scales and beyond. In the stochastic approach to modeling inflationary dynamics, these quantum fluctuations are incorporated as stochastic noise. We employ the formalism of stochastic inflation to examine the role of quantum diffusion during inflation....
We show that a broad power spectrum—modeled as a plateau between infrared and ultraviolet scales—results in a bimodal mass function, with the dominant peak corresponding to heavy PBHs associated with the infrared scale.
This result, based on compaction function statistics, significantly impacts overproduction bounds on the power spectrum amplitude, underscores the need for further...
Accurate predictions of correlators of the primordial curvature perturbation are critical for connecting inflationary models to cosmological observations. Numerical methods employing differential equations, such as the transport approach, have been extensively used to compute the evolution of these correlators.
In this talk, I will present a novel numerical implementation of the transport...
In this talk I will discuss scalar fields in cosmology. Specifically, the impact they can have on early universe thermodynamics and primordial black holes.
In scalar field dark matter models, virialized halos form condensed central cores known as solitons. We extend this idea to the reheating phase of the early universe, a critical period that sets the stage for the emergence of structure after inflation. We study the formation of primordial black holes (PBHs) from the gravitational collapse of virialized configurations arising during this era....
I will present a new mechanism of primordial black hole formation via an interrupted phase transition during the early matter-dominated stage of reheating after inflation. In reheating, induced by the decay of a pressureless fluid dominating the Universe at the end of inflation, dubbed as reheaton, the temperature of the radiation bath typically increases, reaching a maximum temperature...
I will present a novel framework for implementing stochastic inflation on stochastic trees, modelling the inflationary expansion as a branching process. The statistical properties of the curvature perturbation and other cosmological fields are encoded within the tree structure in a manner that fully captures quantum diffusion and its non-perturbative backreaction during inflation. Stochastic...
We discuss a mechanism of primordial black hole (PBH) formation that does not require specific features in the inflationary potential, revisiting previous literature. In this mechanism, a light spectator field evolves stochastically during inflation and remains subdominant during the post-inflationary era. Even though the curvature power spectrum stays small at all scales, rare perturbations...
Accretion plays a crucial role in the evolution of primordial black holes (PBHs) in the early Universe. While earlier works focused on Newtonian Bondi-Hoyle models, general relativistic effects become significant in the hot, dense relativistic plasma of the early cosmos. In this study, we consider both relativistic accretion and Hawking evaporation by solving their coupled evolution equations...
We discuss the possibility of producing the observed baryon asymmetry of the Universe (BAU) and dark matter (DM) from evaporating primordial black holes (PBH) incorporating semi-classical and memory burden regime. In the simplest scenario of baryogenesis via vanilla leptogenesis with hierarchical right handed neutrino (RHN), it is possible to generate the observed BAU with PBH being sole...
Blue-tilted Gravitational Waves (BGWs) have emerged as a promising candidate for explaining the cosmic gravitational wave signals observed by Pulsar Timing Arrays (PTA). Within the standard cosmological model, the frequency range of BGWs is restricted by the Big Bang Nucleosynthesis (BBN) limit on gravitational wave amplitude, which prevents their detection at interferometer scales. However,...
In this talk I will address how “memory-burdened” primordial black holes (PBHs) of low mass, evaporating today, could in principle be detected via their neutrino emission.
Using the latest IceCube data, we place novel constraints on the combined parameter space of PBH masses and memory burden effects. Additionally, we explore whether the ultra-high-energy neutrino event recently detected by...
Mounting theoretical evidence suggests that the information stored in black holes suppresses their decay rate. This effect of memory burden opens up a new window for small primordial black holes (PBHs) below $10^{15}\,{\rm g}$ as dark matter candidates. In this talk, I show that the smooth transition from semi-classical evaporation to the memory-burdened phase strongly impacts observational...
We explore the impact of the back-reaction of evaporation on the quantum state of Primordial Black Holes (PBHs), known as “memory burden”, on the baryon asymmetry production in the Universe through high-scale leptogenesis. Focusing on PBH masses ranging from 1 to 1000 grams, we investigate the interplay between the non-thermal production of heavy sterile neutrinos and the entropy injection...
We introduce and describe $\tt GrayHawk$, a publicly available Mathematica-based tool designed for the efficient computation of gray-body factors for spherically symmetric and asymptotically flat black holes. This program provides users with a rapid and reliable means to compute gray-body factors for massless fields with spin (s = 0, 1/2, 1, 2) in modes specified by the angular quantum...
In the last few years the case that primordial black holes make up a significant fraction of the dark matter has received steadily increasing support from a wide variety of observations. If indeed this is the case then there are a number of observational consequences to be expected. In this talk I shall describe situations where such a population of compact bodies should betray their...
Understanding the evolution of primordial black hole (PBH) populations across cosmic history is critical for reconciling observational data with theoretical formation models. Previous studies showed that gas accretion can significantly alter the mass and spin distributions of PBH binaries from their formation time to the low-redshift universe where gravitational wave signals are observed....
The 21cm signal, soon to be probed by upcoming experiments, is a powerful late-time cosmological tool for constraining Primordial Black Holes (PBHs). Some of the most stringent limits on PBH abundance in the solar mass range are derived using 21cm forecasts. In this talk, I will critically re-examine these forecasts, highlighting the impact of astrophysical uncertainties on the derived...
If primordial black holes (PBHs) of asteroidal mass make up the entire dark matter, they could be detectable through their gravitational influence in the solar system. In this work, we study the perturbations that PBHs induce on the orbits of planets. Detailed numerical simulations of the solar system, embedded in a halo of PBHs, are performed. We find that the gravitational effect of the PBHs...
In this talk, we present our study of the cosmic antiproton and antideuteron fluxes produced by the evaporation of galactic primordial black holes (PBHs) with lognormal initial mass distributions. The antimatter production spectra were obtained using our modified version of the BlackHawk code, which incorporates the new CosmiXs hadronization spectra and a state‐of‐the‐art Wigner function...
Upon their evaporation via Hawking radiation, primordial black holes (PBHs) may deposit energy in the ambient plasma on scales smaller than the typical distance between two black holes, leading to the formation of hot spots around them.
In this talk (based on the recent work https://arxiv.org/pdf/2501.05531), I will consider how the corresponding rise of the local temperature during the...
Observation of an exploding black hole would provide the first direct evidence of primordial black holes, of Hawking radiation, and provide definitive information on the particle spectrum of nature. However, indirect constraints suggest that direct observation of an exploding Schwarzschild black hole is implausible. We introduce a dark-QED toy model consisting of a dark photon and a heavy...
Quasi-normal modes are a crucial feature of black holes and their study is fundamental to understanding these objects. These excitations are not only linear but it has been shown to have a relevant non-linear counterpart, in general difficult to calculate.
The Penrose limit connects a plane wave geometry to the photon ring of a black hole, where the quasi-normal modes are located in the...
If most of the dark matter comprises primordial black holes (PBHs), then numerous constraints imply that they must be in either the asteroidal or solar mass range. Although the first possibility arises naturally if the PBHs formed at the QCD transition, it is sometimes claimed that this possibility is excluded by microlensing surveys and the frequency of gravitational-wave events. However,...
Very little is known about the universe’s history from after the end of inflation until the Big Bang nucleosynthesis (BBN), which spans more than $10^{39}$ orders of magnitude in time scales. In this work, we show that if there was a long period of matter domination in this unknown period, and if the particle causing the matter domination has moderate self-interactions, the matter particles...
I discuss the production of bosonic dark matter by light primordial black holes via superradiance, alongside Hawking emission. In particular, I will show that the resulting dark matter clouds may, under certain conditions, survive as self-gravitating (microscopic) boson stars after the black holes evaporate completely (before BBN). I will also discuss some of the potential implications of this...
Primordial black holes (PBHs) are a compelling dark matter candidate, with their gravitational interactions shaping the evolution of cosmic structure from the earliest times. In this talk, I will present results from our recent fully-collisional simulations of PBH structure formation and binary evolution. We find that the dynamic interactions between PBHs introduce significant feedback...
By extending the so-called excursion-set formalism - often used in the context of Dark Matter halos formation - to two-point statistics, we revisit the initial spatial clustering of Primordial Black Holes (PBHs) originating from the Hubble reentry of large Gaussian density fluctuations in the early Universe. Our work propose a way to correlate the formation of pairs of PBHs, revealing features...
Light Primordial Black Holes (LPBHs) with masses in the range $10$ g $\leq M_{\rm BH} \leq 10^9$ g, although they evaporate before Big Bang Nucleosynthesis, can play a significant role in the production of both Dark Matter and Dark Radiation. In particular, LPBHs can evaporate into light axions or axion-like particles (ALPs) with masses $m_a \lesssim$ MeV, contributing to the effective number...
Motivated by many interesting features present in braneworld cosmology and higher-dimensional gravity, we have reexamined foundational concepts and processes that have previously been studied, such as gravitational collapse, black hole accretion and Hawking emission. In this talk we delve into the phenomenological signatures characteristic of this framework and consider the possibility of the...
Primordial Black Holes (PBHs) are fascinating astrophysical objects that could provide valuable insights into the early universe, cosmology, and gravitational physics.
The standard formation scenario assumes that PBHs originate from the gravitational collapse of large curvature fluctuations generated during inflation. These same large scalar fluctuations, which can lead to PBH formation...
The physics of Primordial Black Holes has garnered significant interest in recent years, largely due to the numerous detections of gravitational
waves originating from BH binary mergers and the hypothesis that some of
these may be of primordial origin.
We show that in realistic models where primordial black holes are formed due to the collapse of sizeable inflationary perturbations, their...
The detection of gravitational waves (GWs) from binary black hole mergers has opened an exciting new avenue for cosmological research. Because GWs interact very weakly with matter, there is potential to observe primordial GWs among the signals captured by current and future detectors. This provides a unique opportunity to probe the early universe physics. Primordial GWs are typically generated...
Mounting evidence suggests that the semi-classical description of a black hole breaks down at the latest after losing an~$O(1)$ fraction of its mass. As a result, effects such as memory burden can slow down evaporation so that small primordial black holes (PBHs), in particular those in the mass range~$10^{6}\, \text{g}$ to~$10^{9}\, \text{g}$, become viable dark matter candidates. I will...
Although there is substantial observational evidence for an
early period of exponential expansion of the Universe, known as
inflation, followed by a subsequent era of radiation domination, the
intermediate period connecting these two epochs, referred to as
reheating, remains challenging to constrain. In this talk, I will
present the primordial black hole (PBH) reheating scenario,...
Primordial black holes (PBHs) serve as a compelling candidate for dark matter and a potential probe of early universe physics. One promising avenue for constraining their abundance is through the stochastic gravitational wave background (SGWB) induced by primordial curvature perturbations. In this talk, I will present how current and future gravitational wave observatories—including Pulsar...
Primordial black holes (PBHs) are possible sources of a gravitational-wave background (GWB), detectable with LISA and the next observing runs of LIGO--Virgo--KAGRA. In case of a detection, it will be crucial to distinguish the possible sources of this GWB. One possibility is to exploit the duty cycle that quantifies the number of sources present in the time domain signal, which can be very...
