Time:  10:00am  (UTC/GMT+8:00, Beijing/Shanghai), Nov. 3 (Wedn.) , 2021

Zoom URL: https://us06web.zoom.us/j/82516408425?pwd=TmI3emNaUVR0RjZQUUpRSE9tcWE1Zz09

Meeting ID: 825 1640 8425

Password: 248437

Speaker: Chi-ming Chang (Tsinghua)

Abstract:

I will discuss the implications of bulk locality on the celestial amplitude. In the context of the four-point amplitude, the fact that the bulk S-matrix factorizes locally in poles of Mandelstam variables is reflected in the imaginary part of the celestial amplitude. In particular, on the positive real axes in the complex plane of the boost weight, the imaginary part of the celestial amplitude can be given as a positive expansion on the Poincare partial waves, which are nothing but the projection of flat-space spinning polynomials onto the celestial sphere. Furthermore, I will derive the celestial dispersion relation, which relates the imaginary part to the residue of the celestial amplitude for negative even integer boost weight. The latter is precisely the projection of low energy EFT coefficients onto the celestial sphere. I will demonstrate these properties explicitly on the open and closed string celestial amplitudes.