Abstract:

The well-established theory of Big Bang Nucleosynthesis (BBN) implies that our  universe must have been thermalized prior to this epoch. However, cosmic inflation leaves the universe cold and dominated by vacuum energy at its end. The subsequent reheating phase, which connects inflation to the radiation-dominated era preceding BBN, plays a pivotal role in shaping the universe’s thermal history. This transition impacts key processes such as dark matter production, cosmic phase transitions, and baryogenesis. Despite its significance, the reheating era remains one of the most observationally challenging epochs in cosmology.  In this talk, I will present recent advances in the study of stochastic gravitational waves (GWs) generated directly during reheating through graviton emission. I will demonstrate how the resulting GW background, as part of the landscape of cosmic messengers, offers a unique and direct probe of the pre-BBN universe.

Biography:

XU Yong received his Ph.D. from the University of Bonn in 2022 and is currently a postdoctoral researcher at the Mainz Institute for Theoretical Physics (MITP), University of Mainz. His research focuses on the intersection of particle physics and cosmology, including model building for cosmic inflation, analyzing the dynamics of reheating, advancing theoretical predictions of gravitational waves from graviton generation, and developing novel scenarios for dark matter production and baryogenesis in the early universe. He has authored 24 research publications to date and was recently awarded a Trottier Space Institute Fellowship at McGill University, starting in October 2025.

Alternative online link：https://meeting.tencent.com/dm/4d7Diz7hWLgd

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