We study the quadratic quasi-normal modes of a Schwarzschild black hole, which are perturbations originating from the coupling of two linear quasi-normal modes. As recent studies suggest, nonlinear effects in black hole perturbation theory may be crucial for accurately describing a black hole ringdown. We present a new class of "quadratic" quasi-normal modes at second order in perturbation...
The direct current (DC) memory is a non-oscillatory, hereditary component of the gravitational wave (GW) signal that represents one of the most peculiar manifestations of the nonlinear nature of GW emission and propagation. In this work, by transforming the results provided in Ebersold et al.[Phys.Rev.D 100 (2019) 8, 084043] in harmonic coordinates and quasi-Keplerian parametrization, we...
In the presence of a finite modular flavour symmetry, fermion mass hierarchies may be generated by a slight deviation of the modulus from a symmetric point. This small parameter governing charged-lepton mass hierarchies may also be responsible for the breaking of lepton number in a symmetry-protected low-scale seesaw. In this talk, I will illustrate the implementation and the phenomenological...
We critically reassess the Minimal Dark Matter model and propose new indirect detection signatures. Specifically, for the originally proposed accidentally stable SU(2) 5-plet, we compute the photon flux arising from Dark Matter Bound State Formation and Sommerfeld Enhancement, highlighting the appearance of several spectral lines. After analyzing the key features of this flux, we explore the...
If reheating occurs at sufficiently low temperatures (below $20 \,\mathrm{MeV}$), neutrinos—assuming they are populated only through weak interactions—do not have enough time to reach thermal equilibrium before decoupling. We present an updated analysis of cosmological models with very low reheating scenarios, including a more precise computation of neutrino distribution functions,...
In trace-free Einstein gravity, the energy-momentum tensor of matter is not necessarily conserved and so the theory offers a natural framework for interacting dark energy models with a constant equation of state w=−1. From the point of view of quantum gravity phenomenology, it has been argued that such violations of energy-momentum conservation might originate from discreteness at the Planck...
Axion-like particles (ALPS), radiated from a network of cosmic strings, may be a large part of Dark Matter (DM). In the era of precision Cosmology, it is possible to characterize the effect of such particles - which almost scale invariant distribution function spans many orders of magnitudes in momentum - on the observables. In this work, we employ the CLASS code and Planck 2018 data to place...
We show that nickel oxide, which is already a very promising target to look for sub-MeV dark matter scattering, can be employed to hunt axion dark matter, with masses in the meV range and couplings to electrons allowing them to potentially be QCD axions. We describe the interactions between axions and the collective excitations of nickel oxide in terms of a universal effective field theory,...
The Cosmic Microwave Background (CMB) provides a powerful tool for testing the existence of light particle species beyond the Standard Model (BSM). In particular, light relics produced via freeze-in are a common feature of models where new light degrees of freedom interact too weakly with the Standard Model (SM) plasma to achieve full thermalization in the early Universe. This talk focuses on...
