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UCD School of Mathematics and Statistics

Scoil na nEolaĆ­ochtaĆ­ Matamaitice UCD

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Professor Tom Laffey wins Hans Schneider Prize (01/02/12)


Posted: 01 February 2012

The Hans Schneider Prize is for research, contributions, and achievements at the highest level of Linear Algebra. The ILAS Executive Board is pleased to announce that the 2012 Hans Schneider Prize in Linear Algebra has been awarded to Thomas J. Laffey, of University College Dublin, Ireland. The award is made in recognition of Laffey's lifetime profound contributions to many areas of Linear Algebra, including integral matrices, simultaneous similarity, linear preservers, and, in particular, his breakthrough results on the inverse eigenvalue problem for nonnegative matrices.

The following are just a couple of examples of Laffey's achievements. He proves (in a joint paper with Reams, 1994) that every square matrix over the integers with trace zero is a commutator of two integral matrices, thus providing an analogue to the classical result over fields. The nonnegative inverse eigenvalue problem (NIEP) asks for a characterisation of those lists of n complex numbers (possibly with repetitions) that comprise the spectra (with multiplicities) of n-by-n entrywise nonnegative matrices. Laffey (in a joint paper with Smigoc, 2006) completely solves the NIEP if the lists are selfconjugate and consist of one positive real number and and n-1 complex numbers with nonpositive real parts. Further, in a recent paper, Laffey brings new insight to the NIEP by giving an ingenious, elementary and constructive proof of the Boyle - Handelman theorem in an important special case.

Laffey is well known in the mathematical community outside of Linear Algebra. He is heavily involved with the Irish team for the International Mathematical Olympiad. Laffey has been a member of the National Committee for Mathematics and represented Ireland at the International Congress of Mathematicians. A member of the Royal Irish Academy since 1981, he served as its Vice President for the period 1990 - 1992. Laffey's encyclopedic knowledge and enthusiasm for mathematics of all kinds have made him an invaluable source of information and advice for his colleagues and students alike.

The Hans Schneider Prize will be presented to Professor Laffey at the next ILAS meeting in Providence USA, 3-7 June, 2013, and Laffey will also be invited to give a lecture at that meeting.
The ILAS Executive would like to express its sincere thanks to the members of the 2012 Hans Schneider Prize Committee: Shmuel Friedland, Leiba Rodman (chair), Peter Semrl, Bryan Shader, and Valeria Simoncini. An outstanding group of people were nominated for the Prize, and the Prize Committee performed its duties with appropriate thoroughness and careful consideration. The Prize Committee's efforts are most appreciated.

 

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