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SUMMARY:Causality in Lovelock theories of gravity - Giuseppe Papallo (Camb
 ridge\, DAMTP)
DTSTART:20160603T140000Z
DTEND:20160603T150000Z
UID:TALK66039@talks.cam.ac.uk
CONTACT:Christian Lund
DESCRIPTION:In Einstein's theory of General Relativity (GR)\, gravity is d
 escribed in terms of curvature of the spacetime\, a four-dimensional Pseud
 o-Riemannian manifold. The field equations\, which relate the curvature of
  spacetime and its matter content\, form a system of quasilinear second-or
 der PDEs in the metric. \nInterestingly\, Lovelock showed that GR is the u
 nique geometric theory of gravity that we can write down in four dimension
 s\, such that the field equations are second order and energy is locally c
 onserved. However\, this 'uniqueness' does not persist in higher dimension
 s. In fact there exist more general theories satisfying these assumptions\
 , the so-called Lovelock theories of gravity. These theories differ from G
 R in that their field equations are fully non-linear and these non-lineari
 ties give rise to several interesting phenomena which don't appear in GR\,
  such as superluminal propagation of signals or formation of shocks. \nI w
 ill discuss some general properties of Lovelock theories\, their causal st
 ructure and the (im)possibility of constructing time machines.
LOCATION:MR13
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