Seminar:- Nonanalyticity and On-Shell Factorization of Inflation Correlators
The dynamics of quantum fields during cosmic inflation can be probed through their late-time boundary correlators. The analytic structure of these boundary correlators contains rich physical information about bulk dynamics and their relationship to cosmological collider observables. In this talk, the speaker will focus on a distinctive nonanalytic behavior known as the nonlocal signal, which emerges at the boundary of the physical region. To facilitate analytic calculations, he will first introduce the Partial Mellin Barnes representation(PMB), which allows his team to study this type of nonanalyticity at both the tree and loop levels. With the utility of PMB, they propose a signal-detection algorithm to identify all potential sources of nonlocal signals in arbitrary graphs and provide an “on-shell” factorization theorem for the leading signal. Additionally, they derive a “cutting rule” for the nonlocal signal as a byproduct, applicable to arbitrary graphs. He should emphasize that their theorem can be understood from a boundary Operator Product Expansion(OPE) viewpoint, but is also applicable to dS-boost-breaking cases. Finally, he will present several examples up to 2-loop to illustrate their theorem. Notably, for certain simple yet nontrivial loop graphs, such as the 4pt triangle and box diagrams, they are able to derive analytic expressions for the leading nonlocal signal and easily extend the calculations to higher orders of squeezeness.
時間：2023.11.22(三) 14:00
地點：香港城市大學 楊建文學術樓 B5-211
講者：Qin Zhe-Han 秦哲涵 (中国 清华大学 博士研究生)
語言：英語
【此屬轉載信息，以主事單位發布為準】
此活動由香港城巿大學物理系主辦。
