Exploring new physics in the early Universe with gravitational waves

Gravitational waves (GWs) provide a window into the early Universe and a direct probe of the epoch prior to Big Bang nucleosynthesis, which is otherwise difficult to access. In this talk, I will discuss recent progress towards detecting the gravitational wave signatures of physics beyond the Standard Model (BSM), focusing in particular on GWs associated with cosmological phase transitions and their potential observation at the future space-based interferometer LISA. I will highlight open questions and future directions, commenting on other promising sources of gravitational radiation in BSM scenarios and complementarity with collider searches.