Polynomial Lower Bounds for the Two-Machine Flowshop Problem with Sequence-Independent Setup Times Anis Gharbi 1,2 , Talel Ladhari 1,3 Princess Fatimah Alnijris’s Research Chair for AMT Department of Industrial Engineering College of Engineering, King Saud University, Riyadh, Saudi Arabia Mohamed Kais Msakni 4 Combinatorial Optimization Research Group – ROI Ecole polytechnique de Tunisie, BP 743, 2078 La Marsa, Tunisia Mehdi Serairi 5 Heudiasyc UMR 6599, Centre de Recherches de Royallieu Universit de Technologie de Compi` egne France Abstract In this paper, we address the problem of two-machine flowshop scheduling problem with sequence independent setup times to minimize the total completion time. We propose five new polynomial lower bounds. Computational results based on ran- domly generated data show that our proposed lower bounds consistently outperform those of the literature. Keywords: Flowshop, setup times, total completion time, lower bounds Electronic Notes in Discrete Mathematics 36 (2010) 1089–1096 1571-0653/$ – see front matter © 2010 Elsevier B.V. All rights reserved. www.elsevier.com/locate/endm doi:10.1016/j.endm.2010.05.138