Academic Lecture: Positivity bounds in effective field theories


Title: Positivity bounds in effective field theories 
Speaker: Prof. Shuang-Yong Zhou (USTC) 
Time: 2:00pm, Monday, Nov.11th, 2019 
Place: Seminar Room 319, IHEP Library Building 

Abstract: Lorentz invariance, locality, unitarity and analyticity are some of the most fundamental properties of quantum field theory. The speaker will show how 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. These positivity bounds take the form of constraints on combinations of the subtracted scattering amplitude and its derivatives. He will first demonstrate the main idea with the simple case of a massive scalar field, and then discuss the technical subtleties that arise when generalizing to cases with nonzero spins. These positivity pounds can be applied to any EFTs. As an illustration, he will apply these positivity bounds to a few well-known EFTs, including Standard Model effective field theory (SMEFT) and massive gravity.