题目：BCS in the Sky: Signatures of Inflationary Fermion Condensation
报告人：祝浴航 博士后 Institute for basic science
时间：2024年6月21号(星期六)下午15:00
地点：LE201
邀请人：Atsuhisa Ota
报告摘要：We consider a Bardeen-Cooper-Schrleffer (BCS)-like model in the inflationary background. We show that with an axial chemical potential, the attractive quartic fermion self-interaction can lead to a BCS-like condensation. In the rigid-de Sitter (ds) limit of inflation where backreaction from the inflaton and graviton is neglected, we perform the first computation of the non-perturbative effective potential that includes the full spacetime curvature effects in the presence of the chemical potential, subject to the mean-field approximation whose validity has been checked via the Ginzburg criterion. The corresponding BCS phase transition is always first-order, when the varying Hubbie is interpreted as an effective Gibbons-Hawking temperature of dS spacetime. In the condensed phase, the theory can be understood from UV and IR sides as fermionic and bosonic, respectively. This leads to distinctive signatures in the primordial non-Gaussianity of curvature perturbations. Namely, the oscillatory cosmological collider signal is smoothly turned off at a finite momentum ratio, since different momentum ratios effectively probe different energy scales. In addition, such BCS phase transitions can also source stochastic graviational wawes,which are feasible for future experiments.
报告人介绍：Dr. Yuhang Zhu is currently a postdoctoral researcher at the institute of Basic Science in Korea. He obtained his PhD in 2023 from the Hong Kong university of science and technology. He works on theoretical cosmology and his recent research interests include cosmological correlators, gravitational waves,and probing new physics in the early universe.
