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VERSION:2.0
PRODID:-//Memento EPFL//
BEGIN:VEVENT
SUMMARY:Conformal actions of semi-simple Lie groups on compact Lorentz man
 ifolds.
DTSTART:20151209T163000
DTEND:20151209T173000
DTSTAMP:20260916T043424Z
UID:fcd12a86870bc16652a36c96f73e65bc47b2e7b39cd31ce32f4b3063
CATEGORIES:Conferences - Seminars
DESCRIPTION:Vincent Pécastaing\nA result of R. Zimmer going back to the 1
 980's asserts that up to local isomorphism\, PSL(2\,R) is the only non-com
 pact simple Lie group that can act by isometries on a Lorentz manifold of 
 finite volume. He presented it as a corollary of another strong result\, k
 nown as "Zimmer's embedding theorem". The latter\, based on ergodic theory
 \, gives strong algebraic constrainst on Lie groups acting on a G-structur
 e by preserving a finite measure and is well adapted to the study of isome
 tric actions in any signature (they preserve the volume form).\nIf we rela
 x the assumption and only consider conformal dynamics of Lie groups\, we l
 ose the existence of an invariant finite measure\, even when the manifold 
 is compact. However\, conformal structures are rigid in dimension at least
  3 and it seems possible to describe conformal Lie group actions.\nI will 
 present a result that extends Zimmer's theorem and classifies semi-simple 
 Lie groups without compact factors acting by conformal transformations on 
 a compact Lorentz manifolds. This work is in the continuation of a result 
 of U. Bader and A. Nevo (2002). I will also discuss the local conformal ge
 ometry of the Lorentz manifolds where such dynamics occur\, especially whe
 n the group that acts is locally isomorphic to PSL(2\,R).
LOCATION:CM010
STATUS:CONFIRMED
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