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SUMMARY:A cautionary case of casual causality – Diagnosing (a)causality 
 in the EFT of gravity - Calvin Chen
DTSTART:20230512T120000Z
DTEND:20230512T130000Z
UID:TALK199522@talks.cam.ac.uk
CONTACT:Isobel Romero-Shaw
DESCRIPTION:In recent years\, causality has emerged as a powerful criterio
 n to distinguish between effective field theories (EFTs) arising from phys
 ical and unphysical high-energy theories.\n \nA direct way to ensure a giv
 en EFT is causal is to demand a lower bound on scattering time delays\, wh
 ich essentially imposes a speed limit averaged over the trajectory. In fla
 t space\, this is unambiguously dictated by the Minkowski light cones\, bu
 t the situation is more subtle with dynamical gravity. I will make the cas
 e that the relevant notion is so-called infrared (IR) causality.\n \nAs an
  example\, I will apply this to study Gauss-Bonnet gravity. Previously we 
 found that\, on spherically symmetric black hole backgrounds\, potential s
 ignatures of IR causality violation are not large enough within the EFT of
  gravity to discard the Gauss-Bonnet operator. The parameter space allowed
  by IR causality is in fact consistent with gravitational positivity bound
 s. Attempts to bypass this conclusion used backgrounds with configurations
  of shockwaves designed to artificially enhance causality violations. In t
 his talk I will emphasise that this is not possible.\n \nThis talk is base
 d on arXiv:2112.05031 and upcoming work in collaboration with C. de Rham\,
  A. Margalit\, and A. Tolley.
LOCATION:Potter room/Zoom
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