I would like to nominate Sanjoy Das as code owner of Scalar Evolution and Induction Variable Simplification.
Scalar Evolution has never had an official code owner, but does regularly need in depth review. Over the past year and a half, Sanjoy has made fantastic contributions to SCEV and has been responsive reviewing patches. He is clearly the authority at this point.
Induction variable simplification doesn't do much but directly apply the results of SCEV analysis. It should have the same owner. IndVars does also contain a sign-extend elimination algorithm, but that's primarily a legacy pass and I don't expect much work on it.