A Combinatorial Object

Hadamard matrix of order 428

F26A Graph

Description: A Hadamard matrix is a square matrix whose entries are either +1 (white pixels) or -1 (black pixels) and whose rows are mutually orthogonal. A Hadamard matrix of order 428, the smallest unknown order of Hadamard matrices before June 2004, was built by Hadi Kharaghani and Behruz Tayfeh-Rezaie. Since June 2004, the order 668 has been the smallest multiple of 4 for which no Hadamard matrix is yet known. It is conjectured that examples of order 4n exist for all n.

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About the IPM Combinatorics and Computing Group
Combinatorics is a branch of mathematics that studies finite collections of objects that satisfy certain criteria. Over the past few decades, combinatorics has become an increasingly important part of mathematics. It has strong connections to other areas of mathematics like algebra, number theory and operations research as well as other disciplines such as theoretical computer science, cryptography, information theory, social sciences and biological sciences.
IPM Combinatorics and Computing Group was officially established in 2009 at the School of Mathematics of IPM, although it had been active since the foundation of IPM in 1989. During 1989-2009, the group was directed by G. B. Khosrovshahi, a founding member of IPM. The group plays an important role in carrying out research in combinatorics and computing and related fields in Iran. Researchers from universities across the country collaborate with the group in different capacities: senior researchers, resident researchers, nonresident researchers and students. The group also has some faculty members and postdoctoral research fellows. The researchers of the group have published a lot of papers in top quality international journals. Many renown mathematicians from around world have visited IPM and have had collaborations with the group researchers. The group has organised a number of international conferences covering areas such as graph theory, design theory and computational methods. Weekly seminars on combinatorics and computing is also held since 1992.
The main research areas of the group are:

  • Algebraic combinatorics
  • Algebraic graph theory
  • Computational methods for constructing combinatorial objects
  • Computational complexity
  • Cryptography
  • Flows on graphs and designs
  • Graph coloring
  • Quantum computing
  • Quantum information theory


  • Contact Us
    Head of the Group: Omran Ahmadi

    Email Address: oahmadid at ipm dot ir

    Tel: +98 21 2310 ext. 2266

    Fax: +98 21 22290648

    Mailing Address: School of Mathematics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5746, Tehran, Iran

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