Feebly interacting particles (FIPs), such as axions, scalars, dark photons, and majorons, are often theoretically well motivated, and a dark sector including one or more of them can both have the aesthetic draw of solving several problems simultaneously (like the QCD axion, an excellent DM candidate and a consequence of the Peccei-Quinn solution to the strong CP problem), and be a valid alternative to the weakly interacting massive particle paradigm. In this talk, I will discuss some fresh developments in direct detection and astrophysical probes for axions and other FIPs. In the first half of the talk, I will present the plasma haloscope, a detection scheme that enables resonant conversion by matching the QCD axion mass to a plasma frequency, therefore converting axions to plasmons. The second part of the talk is dedicated to complementary searches for axions and other FIPs through astrophysical observables. I will show that recent ideas probe uncharted parts of the FIP parameter space, sometimes largely surpassing previous arguments.
DFA and INFN, Sezione di Padova
