HEP Theory Journal Club

Gravitational positivity bounds: implications for the swampland program

Junsei Tokuda

Non-trivial relations between ultraviolet complete quantum gravity and its low energy effective field theories (EFTs) can have important phenomenological implications. Such relations are so-called swampland conditions. In this talk, we develop a method which may be useful to derive swampland conditions by extending so-called S-matrix positivity bounds to the gravitational context. Our method assumes several properties of four-point amplitudes at high energies such as the Reggeization of graviton exchange. Under additional assumptions on the details of the Regge behavior, we find that implications of positivity bounds on gravitational EFTs are interesting. In particular, we find strong bounds on the simplest dark photon models which can be compared with experimental bounds, while the Standard Model easily satisfies the gravitational positivity bounds. These results give phenomenological motivations for further studies of the Regge behavior. In the last part of this talk, we briefly introduce our recent attempt to constrain gravitational Regge amplitude based on the so-called finite energy sum rules (FESRs).