1pm - 2pm: Detector amplitudes: how positivity meets the real world

Long-range interactions, mediated by photons and/or gravitons, force exclusive S-matrix elements to vanish in D = 4 flat space-time, due to infrared divergences. This poses a challenge to programs, such as positivity and S-matrix bootstrap, that directly rely on the properties of exclusive 2-to-2 amplitudes. In this talk, I will introduce stripped amplitudes as IR-finite, analytic, crossing-symmetric and Regge-behaved avatars of standard amplitudes, associated with a physical detector length scale. In the regime in which the latter is taken exponentially larger than all other scales, they also satisfy a form of unitarity, allowing to derive IR-finite positivity bounds on EFTs, in presence of long-range interactions.