报告题目：Crescendo Beyond the Horizon: More Gravitational Waves from Domain Walls Bounded by Inflated Cosmic Strings

报 告 人：Yunjia Bao 包昀嘉 (The University of Chicago)

报告时间：2025年9月11日13：30

报告地点：物理楼W260

内容摘要： Gravitational-wave (GW) signals offer a unique window into the dynamics of the early universe. GWs may be generated by the topological defects produced in the early universe, which contain information on the symmetry of UV physics. We consider the case in which a two-step phase transition produces a network of domain walls bounded by cosmic strings. Specifically, we focus on the case in which there is a hierarchy in the symmetry-breaking scales, and a period of inflation pushes the cosmic string generated in the first phase transition outside the horizon before the second phase transition. We show that the GW signal from the evolution and collapse of this string-wall network has a unique spectrum, and the resulting signal strength can be sizeable. In particular, depending on the model parameters, the resulting signal can show up in a broad range of frequencies and can be discovered by a multitude of future probes, including the pulsar timing arrays and space- and ground-based GW observatories. As an example that naturally gives rise to this scenario, we present a model with the first phase transition followed by a brief period of thermal inflation driven by the field responsible for the second stage of symmetry breaking. The model can be embedded into a supersymmetric setup, which provides a natural realization of this scenario. In this case, the successful detection of the peak of the GW spectrum probes the soft supersymmetry breaking scale and the wall tension. This talk is based on the work [arXiv:2407.17525].

报告人简介：Yunjia Bao is a Ph.D. student at UChicago, advised by Lian-Tao Wang. He completed his undergraduate program at Reed College and the master’s program at Brown University. He focuses on high-energy particle phenomenology, piecing together puzzles that could explain mysterious dark matter, baryon asymmetry, cosmic inflation, and elusive new particles. He likes to explore novel experimental signatures and to bridge formal theoretical frameworks with exciting future experiments.