Positivity With Long-Range Interactions

par Marcello Romano (IPhT)

mercredi 18 mars 2026, 14:45 → 16:00 Europe/Paris

Amphithéâtre Léon Motchane (IHES)

Séminaire Amplitudes et Gravitation sur l'Yvette (IHES/IPhT)

Long-range interactions, mediated for instance 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 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 scale $\Lambda$. In the regime in which the latter is taken exponentially small 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.

 

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