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SUMMARY:Graviton time-delay in Lovelock gravity - Giuseppe Papallo\, DAMTP
DTSTART:20151023T120000Z
DTEND:20151023T130000Z
UID:TALK61390@talks.cam.ac.uk
CONTACT:43345
DESCRIPTION:Lovelock theories provide a natural generalisation to GR in hi
 gher dimensions. Interestingly\, in these theories gravitons can propagate
  faster or slower than light.\nIt was recently observed (Camanho et al. 20
 14) that\, in a Lovelock theory\, gravitons can experience a negative Shap
 iro time delay when crossing a gravitational 'shock-wave'. Using this effe
 ct it was then argued that closed causal curves may form\, making the theo
 ry unviable.\nInstead of the singular shock-wave geometries\, we will cons
 ider gravitons propagating on smooth black hole spacetimes and show that a
  negative time delay is possible in this setting. We will then discuss iss
 ues related to the construction of closed causal curves and why the existe
 nce of causally pathological solutions wouldn't be sufficient to discard t
 he theory.
LOCATION:Pavilion B Potter Room (B1.19)
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