Lorentzian manifolds with a conformal action of SL(2,R)
Lorentzian manifolds with a conformal action of SL(2,R)
We consider conformal actions of simple Lie groups on compact Lorentzian manifolds. Mainly motivated by the Lorentzian version of a conjecture of Lichnerowicz, we establish the alternative: Either the group acts isometrically for some metric in the conformal class, or the manifold is conformally flat - that is, everywhere locally …