Professor Patric R. J. Östergård's home page

The University of Pécs conferred the degree of "Doctor et Professor Honoris Causa" on me at a ceremony held in Pécs, Hungary, on 7 November 2013.

Research interests

• Mathematical objects
  • Codes (covering codes, error-correcting codes, etc.)
  • Combinatorial designs
  • Other structures that can be viewed as packings or coverings
• Combinatorial algorithms
  • Stochastic optimization methods, local search algorithms (tabu search)
  • Exact algorithms for (NP-)hard problems
  • Graph algorithms for clique and coloring problems
  • Algorithms for isomorphism testing; classification algorithms
• Information theory, in general
• Discrete mathematics, in general

Recent and old news

Recent: Jointly with Michael Braun, Tuvi Etzion, Alexander Vardy, and Alfred Wassermann, we found the first nontrivial q-analog of a Steiner system; this was also reported elsewhere. Jointly with Leonard Soicher, we showed that there is no McLaughlin geometry.

Old: In 2004, Petteri Kaski and I showed that there are 11,084,874,829 Steiner triple systems of order 19; all of those billions of objects can be obtained here. In 2009, Olli Pottonen and I showed that there are 5983 perfect binary one-error-correcting codes of length 15.

Together with Sampo Niskanen, we have developed Cliquer, routines for clique searching. The first public release (1.0) was made in late 2002; the current release (1.21) can be found here.

I am a recipient of the 1996 Kirkman Medal, awarded by the Institute of Combinatorics and its Applications.

I am co-Editor-in-Chief of the Journal of Combinatorial Designs and on the editorial boards of Ars Combinatoria and the Bulletin of the Institute of Combinatorics and its Applications.

My research is financed in part by the Academy of Finland.

Publications

New lower bounds on binary constant weight error-correcting codes, M. Braun, J. Humpich, A. Laaksonen, and P. R. J. Östergård, Journal of Combinatorial Mathematics and Combinatorial Computing, to appear.

Sparse Steiner triple systems of order 21, J. I. Kokkala and and P. R. J. Östergård, Journal of Combinatorial Designs, to appear.

Quaternary complex Hadamard matrices of order 18, P. R. J. Östergård and W. T. Paavola, Journal of Combinatorial Designs, to appear.

Other interests