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SUMMARY:Amplitudes’ Positivity in Gravitational Theories\, and the Weak 
 Gravity Conjecture - Brando Bellazzini(IPhT\, Saclay) 
DTSTART:20191118T130000Z
DTEND:20191118T140000Z
UID:TALK131545@talks.cam.ac.uk
CONTACT:Sadra Jazayeri
DESCRIPTION:I will discuss new positivity bounds for scattering amplitudes
  in theories with a massless graviton in the spectrum in four spacetime di
 mensions. The bounds imply that extremal black holes are self-repulsive\, 
 \nM/|Q|< 1 in suitable units\, and that they are unstable to decay to smal
 ler extremal black holes\, hence providing an S-matrix proof of the weak g
 ravity conjecture. I will also present applications of these bounds to mod
 ified gravity theories\, such as weakly broken galileons\, showing that th
 ey have a very low cutoff\, much smaller than their strong coupling scale.
LOCATION:CMS\, Pav. B\, CTC Common Room (B1.19) [Potter Room]
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