Towards flat-space holography: S-matrix, Celestial Amplitudes and the UV/IR Physics

The discussion will be based on the recent paper 2012.04207 by Arkani-Hamed, Pate, Raclariu and Strominger (and references therein) concerning the understanding of flat space physics from objects, the celestial amplitudes, living at null infinity. After an introduction to the subject, I will discuss how, as a consequence of being defined via boost eigenstates, celestial amplitudes are highly sensitive to UV physics, breaking the usual Wilsonian decoupling between UV and IR physics