  We investigate the recoverable robust single machine scheduling problem under
interval uncertainty. In this setting, jobs have first-stage processing times p
and second-stage processing times q and we aim to find a first-stage and
second-stage schedule with a minimum combined sum of completion times, such
that at least Delta jobs share the same position in both schedules.
  We provide positive complexity results for some important special cases of
this problem, as well as derive a 2-approximation algorithm to the full
problem. Computational experiments examine the performance of an exact
mixed-integer programming formulation and the approximation algorithm, and
demonstrate the strength of a proposed polynomial time greedy heuristic.
