- I would like to know of a reference for the derivation of the quadratic order terms for the Riemann tensor, scalar curvature and Ricci tensor and for √−g?
Many introductory GR books and lectures: Carroll, Weinberg, Feynman lectures on gravitation, Misner, etc. You should work it out on your own, though. You just need to split the metric in a background plus a fluctuation and treat the fluctuation as a tiny perturbation.
- Further on such an expression how does one impose that the background is say AdS? (even for the linear case as linked above)
The background metric is the AdS metric instead of Minkowski. What in a flat background are the components of Minkowski metric are the components of AdS.