Lorentzian similarity manifold
  If an $m+2$-manifold $M$ is locally modeled on $\RR^{m+2}$ with coordinate changes lying in the subgroup $G=\RR^{m+2}\rtimes ({\rO}(m+1,1)\times \RR^+)$ of the affine group ${\rA}(m+2)$, then $M$ is said to be a \emph{Lorentzian similarity manifold}. A Lorentzian similarity manifold is also a conformally flat Lorentzian manifold because $G$ is isomorphic to the stabilizer of the Lorentz group ${\rPO}(m+2,2)$ which is the full Lorentzian group of the Lorentz model $S^{2n+1,1}$. It contains a class of Lorentzian flat space forms. We shall discuss the properties of compact Lorentzian similarity manifolds using developing maps and holonomy representations. 
Yoshinobu Kamishima
math.GT