In this talk, I consider spectator scalar fluctuations generated by gravity during inflation and reheating. This framework can be applied to the production of Dark Matter (DM) or Standard Model (SM) scalar degrees of freedom. I first review the perturbative approach describing gravitational portals from gravity EFT and solving the Boltzmann equation for the distribution function of scalar...
The transition between cosmic inflation to a phase of radiation domination, e.g. reheating, is an essential ingredient of any theory of inflation. The reheating stage is typically characterized by an inflaton oscillating about the minimum of its potential. Such dynamics, inducing the growth of inhomogeneities and non-perturbative dynamics have been shown to be relevant for a reheating stage...
Primordial black holes (PBHs) lighter than 10^9 g are expected to have fully evaporated before the big bang nucleosynthesis, leaving their past abundances unconstrained by observations. Depending on their initial abundance, these PBHs could have temporarily dominated the Universe or remained as a subdominant component. In this talk, I explore the cosmological implications of such light mass...
We study the scalar-induced gravitational wave (SIGW) signal from the evaporation of primordial black holes (PBHs). In the idealised monochromatic case, a pronounced SIGW signal is produced via the Poltergeist mechanism, driven by a sudden transition from matter to radiation dominance. However, realistic extended mass distributions - such as those predicted by the Press-Schechter formalism...
In this work, we study the cosmological implications of an initial displacement of the Peccei-Quinn breaking field generated during inflation and the subsequent oscillations of the field around its minimum. These oscillations induce a parametric resonance effect, leading to the exponential growth of perturbations. In our analysis, we employ lattice simulations to investigate the abundance of...
The matter-antimatter asymmetry of the Universe represents one of the main open questions in particle physics and cosmology. In this talk, we will present a novel realization of cold baryogenesis, a mechanism involving the formation and decay of Standard Model SU(2)-textures, that relies on the out-of-equilibrium dynamics during a strong first order electroweak phase transition. By performing...
We present the audible axion mechanism extended by a period of supercooling that delays the onset of axion oscillations.
While the original setup relies on a large axion decay constant and coupling to a dark Abelian gauge field to produce sizable gravitational wave signals, in this talk we discuss how supercooling opens up the testable parameter space and reduces the required coupling to...
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 talk, I will talk about recent work where we explore the consequences of imposing causal propagation on the comoving curvature perturbation in the EFT of inflation,...
In this talk I will present a recent investigation where we show that multi-field inflationary models with negligible turning in field space during inflation can lead to an effective sourcing of adiabatic from entropic perturbations after the end of inflation. I will illustrate this general phenomenon with a detailed analysis of an inflationary model whose scalar potential is determined by...
We investigate whether an Early-Universe stochastic gravitational–wave background (SGWB) can account for the common‐spectrum process reported by NANOGrav, while also being consistent with current and projected CMB measurements of extra radiation. We compute the contribution of the effective number of relativistic species, $\Delta N_{eff}$, for a number of Early-Universe models proposed to...
We propose a novel cosmological scenario to explain the exceptional KM3-230213A neutrino event reported at an energy scale of O(100) PeV by the KM3NeT collaboration, along with its associated gravitational wave signatures. In our framework, ultra-high-energy neutrinos originate from the decay of a super-heavy sterile neutrino produced via the Hawking evaporation of primordial black holes in...
