Bridging gaps and jumping into the void: new opportunities in the spectrum of GWs

In this talk I’ll highlight the existence of gaps in the spectrum of GWs poorly explored by current observations and that may contain information about BSM physics or primordial cosmology. I’ll focus on the muHz gap, and explain how to use the resonance absorption of GWs by binary systems (as the Earth-Moon system or binary pulsars) to access this band. I’ll also highlight the potential of high frequency (\omega > kHz) GWs. The focus of this second part will be the use of cavities to detect these signals, together with a brief discussion of sources and what can be learned from them.