Iberian Strings Meetings 

21/01/2021, 12:30 — 13:00 — Online
Mario Herrero, SISSA

Amplitudes Positivity and IR-UV connections in Graviton Exchange

Positivity bounds are standard tools to assess the validity of EFTs for which a unitary, local and Lorentz Invariance UV completion is assumed. They impose positivity of certain (combination of) Wilson coefficients by connecting IR physics to features of the UV completion through dispersion relations of scattering amplitudes. If the corresponding EFT does not satisfy these bounds, it is assumed to lay on the Swampland.

However, the standard derivation of positivity bounds fails when the exchange of a massless particle is possible, which excludes the very important case of gravitational interactions. In this talk we show how to derive new positivity bounds that take into account this issue. We generalize the standard derivation by writing dispersion relations which are valid when production of massless particles is included.

Furthermore, we show that one can obtain efficient bounds in the case of gravity if one assumes the high energy limit of the scattering amplitude to be of the Regge form, as implied from String Theory. We will discuss implications of these bounds for different physical settings, such as models of interacting scalar fields, scalar QED, and the Weak Gravity Conjecture.

See also

IS_2021_herrero.pdf