Fischer, David SimonDavid SimonFischerGyörgyi, PéterPéterGyörgyi2023-09-012023-09-012023-04-25Annals of Operations Research (2023)https://hdl.handle.net/11420/43117In this paper we consider the coupled task scheduling problem with exact delay times on a single machine with the objective of minimizing the total completion time of the jobs. We provide constant-factor approximation algorithms for several variants of this problem that are known to be N P-hard, while also proving N P-hardness for two variants whose complexity was unknown before. Using these results, together with constant-factor approximations for the makespan objective from the literature, we also introduce the first results on bi-objective approximation in the coupled task setting.en0254-5330202313871408Springerhttps://creativecommons.org/licenses/by/4.0/Approximation algorithmsCoupled task problemSingle machine schedulingTotal completion timesMathematicsTechnologyJournal Article10.15480/882.847810.1007/s10479-023-05322-510.15480/882.8478Journal Article