Rüdiger Stephan

Phone:	+49-30-314-28323
Room:	MA 307
Email:	[last name]@math.tu-berlin.de
Office hours:	by appointment

Teaching

Research Interests

• Cardinality Constrained Combinatorial Optimization Problems
• Path and Cycle Polyhedra
• Extended Formulations
• Binpacking: The Steel Mill Slab Problem

Short Academic CV

Projects

• Cardinality Constrained Combinatorial Optimization
• Cycle and Path Polytopes with and without Length Restrictions
• Projections from Dynamic Programming Based Extended Formulations

Publications

• Polytopes associated with length restricted directed circuits, Master Thesis, Technische Universität Berlin, 2005
• On the cycle polytope of a directed graph and its relaxations (jointly with Egon Balas). In: Operations Research Proceedings 2006, pp.203-208, Springer, 2007.
• -------------------------, Networks 54 (1), 2009, 47-55.
• Facets of the (s,t)-p-path polytope, Discrete Appl. Math. 157 (14), 2009, 3119-3132.
• Polyhedral aspects of cardinality constrained combinatorial optimization problems, Doctoral Dissertation, Technische Universität Berlin, 2009.
• Solving Steel Mill Slab Problems with Branch-and-Price (jointly with Stefan Heinz and Thomas Schlechte), ZIB-Report 09-14, 2009.
• On cardinality constrained cycle and path polytopes (jointly with Volker Kaibel), Math. Program. (Ser. A) 123 (2), 2010, 371-394.
• Cardinality constrained combinatorial optimization: Complexity and polyhedra, Discrete Optim. 7 (3), 2010, 99-113.
• On cardinality constrained polymatroids (jointly with Ingo Spiegelberg), Electronic Notes in Discrete Mathematics 36, 2010, 1017-1024.
• An extension of disjunctive programming and its impact for compact tree formulations, 2010, arXiv:1007.1136v1 [math.OC].
• On the cardinality constrained matroid polytope (jointly with Jean François Maurras), to appear in Networks.
• On the connectivity of k-clique polytopes (jointly with Jean François Maurras and Roumen Nedev), ZIB-Report 10-29, 2010.
• Smaller compact formulation for lot-sizing with constant batches, ZIB-Report 10-30, 2010.

Miscellaneous

• 16. Berliner Tag der Mathematik
• Stefan Heinz, Thomas Schlechte, and Jonas Schweiger, MOPTA2009 Challenge - Let the trucks roll!

Talks and Workshops

10th International Workshop on Combinatorial Optimization
Aussois, France, January 8-13, 2006.

Operations Research 2006
Universität Karlsruhe, September 6-8, 2006
Talk on Facets of the cycle polytope unrelated to the traveling salesman polytope.

Workshop on Mixed Integer Programming 2007
Centre de Recherche Mathematique, Montreal, Canada, July 30 - August 02, 2007
Presentation of poster Cardinality Constrained Path and Cycle Polytopes.

Tag der Mathematik Berlin 2008
Freie Universität Berlin, April 26, 2008
Talk on Der kürzeste Weg zum Ziel.

Cologne Twente Workshop 2008
Gargnano, Lake Garda, Italy, May 13-15, 2008
Talk on The cardinality constrained matroid polytope.

FRICO 2008
Universität Heidelberg, September 25-28, 2008
Talk on Polyhedral Analysis of Cardinality Constrained Combinatorial Optimization Problems.

13th Workshop on Combinatorial Optimization
Aussois, France, January 11-17, 2009.
Talk on Polyhedral Aspects of Cardinality Constrained Combinatorial Optimization.

Cologne Twente Workshop 2009
Ecole Polytechnique and CNAM, Paris, France, June 2-5, 2009
Talk on Classification of 0/1-facets of the hop constrained path polytope defined on an acyclic digraph.

Lange Nacht der Wissenschaften 2009
ZIB, Berlin, June 13, 2009
Talk on Farbenfreude in der Stahlindustrie: Ein Kinderspiel?

20th Meeting of the International Symposium for Mathematical Programming
Chicago, USA, August 23-28, 2009.
Talk on Characterization of 0/1/-1 Facets of the Hop Constrained Path Polytope by Dynamic Programming.

14th Workshop on Combinatorial Optimization
Aussois, France, January 4-8, 2010.
Talk on Characterization of facets of the hop constrained chain polytope using projection.

International Symposium on Combinatorial Optimization
Hammamet, Tunisia, March 24-26, 2010.
Talk on On cardinality constrained polymatroids.

Symposium ``Diskrete Mathematik''
Vienna, Austria, May 14-15, 2010.
Talk on Extended formulations in connection with perfect matchings, T- cuts, and Gomory-Hu trees.

First Cargese Workshop in Combinatorial Optimization
Cargese, Corse, France, September 19-24, 2010.
Talk on An extension of disjunctive programming and its impact to compact tree formulations.