The weak equivalence principle (WEP) is the cornerstone of General Relativity (GR). Testing
it is thus a natural way to confront GR to experiments, which has been pursued for four …

A bstract The relic density of Dark Matter (DM) in the freeze-in scenario is highly dependent
on the evolution history of the universe and changes significantly in a non-standard (NS) …

Exploring dark matter via observations of extreme astrophysical environments--defined here
as heavy compact objects such as white dwarfs, neutron stars, and black holes, as well as …

A bstract The existence of right-handed neutrinos, or heavy neutral leptons (HNLs), is
strongly motivated by the observation of neutrino masses and mixing. The mass of these …

A bstract Proton beam dump experiments are among the most promising strategies to
search for light and feebly interacting states such as axion-like particles (ALPs). The …

Axion-like particles (ALPs) may be abundantly produced in core-collapse (CC) supernovae
(SNe); hence, the cumulative signal from all past supernova (SN) events can create a diffuse …

A bstract Axion-like particles (ALPs) interacting with the Standard Model can be abundantly
produced in proton beam fixed-target experiments. Looking for their displaced decays is …

The kinetic mixing (KM) portal is a popular mechanism that allows light dark matter (DM) in
the mass range below∼ 1 GeV to achieve the observed relic density by thermal means and …

A bstract We show that the couplings of axions to gauge bosons are highly restricted in
Grand Unified Theories where the standard model is embedded in a simple 4D gauge …

In these notes I try to introduce the reader to the topic of axions: their theoretical motivation
and expected phenomenology, their role in astrophysics and as dark matter candidate, and …