Lessons from Axion Dark Matter for the Field of Gravitational Waves

Abstract: A decade ago, the discovery of gravitational waves marked a crucial milestone in our understanding of the universe. While ongoing efforts primarily focus on detecting gravitational waves at frequencies below a few kHz, a growing interest in exploring higher frequencies is emerging, driven by the potential to observe signals of cosmological origin. In the first segment of my talk, I will delve into the backgrounds for such signals within the Standard Model, with a particular emphasis on the dominant source on Earth: the high-temperature plasma in the Sun. I will highlight the strong parallel with solar axions. Shifting focus in the second part, the discussion will center on experimental proposals for detecting high-frequency gravitational waves. Specifically, I will discuss the potential of axion haloscopes to probe gravitational waves in the 100 kHz-100 MHz range.