A note on static spaces and related problems
  We solve the classifying problem raised by Fischer and Marsden for Bach flat static spaces. We also prove the conjecture about critical point equations proposed by Besse for Bach flat manifolds. Particularly in dimension 3, we derive an integral identity that allows us to obtain conformal flatness from the vanish of the full divergence of the Cotton tensor for static metrics and metrics satisfying the critical point equation. 
Jie Qing and Wei Yuan
math.DG