报告题目：Are all EFTs Created Equal?

报告人：周双勇  教授（中国科学技术大学）

报告时间：2020 年 7 月 16 日（周四）15：30

报告地点：在线报告（ 腾讯会议 ID : 233 867 570）

报告摘要：

Lorentz invariance, locality, unitarity and analyticity are some of the most fundamental properties of S-matrix/quantum field theory. I will explain why requiring a local, analytic, unitary UV completion for a low energy effective theory (EFT) can impose positivity bounds on the Wilson coefficients of the EFT. I will first demonstrate how the forward limit positivity bound is derived, and then show how to obtain an infinite series of positivity bounds that are for arbitrary spins, with t derivatives and valid away from the forward limit. These positivity bounds take the form of constraints on combinations of the subtracted scattering amplitude and its derivatives. For the scalar case, we also show how to extract more positivity bounds by judiciously utilizing the partial wave expansion in the dispersion relation and the triple crossing symmetry of the amplitude. For the forward limit, we find a novel approach based on the convex cone structure of the bounds and obtain new bounds corresponding to scatterings of entangled states, which go beyond elastic positivity. These positivity pounds can be applied to any EFTs. As an illustration, I will apply these positivity bounds to the Standard Model effective field theory (SMEFT) and also briefly mention a few other applications we have sought.

报告人简介：周双勇，中国科学技术大学教授，2005年本科毕业于山东大学，2008年硕士毕业于山东大学，2012年于英国诺丁汉大学获得博士学位，2012年起先后在意大利SISSA、美国Case Western Reserve University、英国Imperial College London等地做博士后工作，2017年至今在中国科学技术大学工作，任教授。