1pm - 2pm: Topological Defects as Windows into the early Universe

Topological defects formed in the early Universe offer a unique window into high-energy physics. In this talk, I will focus on two such phenomena. First, I will discuss cosmic strings generated during the breaking of Grand Unified Theories (GUTs) to the Standard Model and show how their gravitational wave signals, when combined with proton decay searches, can constrain GUT breaking chains and high-scale baryogenesis. I will then turn to domain walls arising from the spontaneous breaking of non-Abelian discrete symmetries, such as those used in lepton flavour models. Their rich vacuum structure and late-time annihilation can also produce observable gravitational wave signatures, providing a complementary probe of flavour physics at very high energies.