Title: Dark Matter Dynamics and Gravitational Waves from Hidden Sectors

Speaker: Professor Wanzhe Feng (School of Science, Tianjin University)

Time: 15:00pm, May 13, 2026

Location: 3-309, PMO Xianlin Campus

Abstract: The steadily increasing sensitivity and precision of direct and indirect detection experiments have significantly narrowed the viable parameter space of many conventional WIMP scenarios. This leads to two related challenges. First, the effective coupling between dark matter and the Standard Model is often forced to be ultraweak. Such a small coupling makes it increasingly difficult to obtain an annihilation cross section large enough to deplete the dark matter abundance to the observed relic density, posing a serious challenge for freeze-out model building. Second, the same ultraweak coupling makes the dark sector in which dark matter resides difficult to probe directly, thereby motivating multi-messenger searches for dark sectors. In this talk, motivated by these two issues, I will discuss the interplay among multiple hidden sectors, with particular emphasis on the role of dark sector dynamics in the cosmological evolution of dark matter. I will also discuss one of the most important multi-messenger probes beyond traditional dark matter searches: gravitational waves from cosmological phase transitions. In particular, I will present gauge-independent gravitational wave predictions from a minimal U(1) dark sector.