Speaker
Description
Axion-like particles (ALPs) are a common feature in many extensions of the Standard Model. However, their stability is not guaranteed by any symmetry, making the consideration of their lifetime crucial when investigating their cosmological consequences. In this talk, I will explore two distinct ALP mass regimes and their corresponding signatures. First, I will focus on sub-eV ALPs, presenting recent advancements in predictions for ALP dark radiation. I will introduce a phase-space approach to refine the predictions for the ALP dark radiation abundance and demonstrate how spectral distortions are typically expected due to non-instantaneous decoupling. In the second part, I will turn to GeV-scale ALPs, which act as a portal between the visible sector and a scalar dark matter (DM) candidate. I will discuss how the interaction between the ALP and the DM reveals a deep connection to the underlying global symmetry that stabilizes the DM particle, highlighting the key features of this scenario: a relic density independent of ALP couplings to the visible sector and enriched indirect detection spectra.
