H-infinity control — reaches the same envelope by a different route than → Reachability analysis

Both are imported from control theory to define a conservative operating envelope, but they compute that envelope with different mathematics. H-infinity control is a worst-case optimal-control framework: given that disturbances are bounded in magnitude, find the policy minimizing the worst-case deviation in system response, a minimax computation over a continuous disturbance set. Reachability analysis instead computes, for a given policy and dynamics model, the set of states that can actually be reached or returned to — a set-membership computation, not an optimization over disturbances. Concrete Problems invokes H-infinity control specifically alongside bounded exploration (concrete-problems, §"Bounded Exploration:", p. 15) and reachability analysis alongside impact regularization and out-of-distribution response (concrete-problems, §"Define an Impact Regularizer:", p. 5), suggesting the paper treats them as substitutable building blocks for the same kind of conservative-envelope guarantee rather than as parts of one combined method.