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CATEGORIES:Junior Geometry Seminar
SUMMARY:Causality in Lovelock theories of gravity - Giusep
pe Papallo (Cambridge\, DAMTP)
DTSTART;TZID=Europe/London:20160603T150000
DTEND;TZID=Europe/London:20160603T160000
UID:TALK66039AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/66039
DESCRIPTION:In Einstein's theory of General Relativity (GR)\,
gravity is described in terms of curvature of the
spacetime\, a four-dimensional Pseudo-Riemannian m
anifold. The field equations\, which relate the cu
rvature of spacetime and its matter content\, form
a system of quasilinear second-order PDEs in the
metric. \nInterestingly\, Lovelock showed that GR
is the unique geometric theory of gravity that we
can write down in four dimensions\, such that the
field equations are second order and energy is loc
ally conserved. However\, this 'uniqueness' does n
ot persist in higher dimensions. In fact there exi
st more general theories satisfying these assumpti
ons\, the so-called Lovelock theories of gravity.
These theories differ from GR in that their field
equations are fully non-linear and these non-linea
rities give rise to several interesting phenomena
which don't appear in GR\, such as superluminal pr
opagation of signals or formation of shocks. \nI w
ill discuss some general properties of Lovelock th
eories\, their causal structure and the (im)possib
ility of constructing time machines.
LOCATION:MR13
CONTACT:Christian Lund
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