Australia loses a world-class maths wizard and chess champ
February 8, 2011

GREGORY JOHN HJORTH
MATHEMATICIAN, CHESS PLAYER
14-6-1963 — 13-1-2011
By GUY RUNDLE

‘YES, I’m a mathematician, but look, it’s 20 years since I’ve done any counting,” Greg Hjorth, who has died of a heart attack in Carlton, was wont to say.

He was 47.

Holding professorial posts at both Melbourne University and the University of California Los Angeles, he made important and original contributions to set theory and a range of other related fields.

In Australia he was also famous as a chess champion with a unique personal style. In both fields with more than their fair share of the personality-challenged, he was widely known as a gentle, generous and likeable soul.

Well-known as a rising young star when he gained his PhD from the University of California at Berkeley in 1993 – his dissertation was awarded the inaugural Sacks prize for the world’s best mathematical logic thesis that year – he had already done original work at Melbourne University, where he had completed combined honours in mathematics and philosophy in 1988.

Set theory, his preferred focus, has been at the foundation of modern mathematics since its creation in the 19th century, and the objects of this realm – Borel equivalence relations, the Vaught conjecture – are as strange and mysterious as deep-ocean sea life. But Hjorth immediately made what his colleague Alexander Kechris has described as ”a series of stunning and far-reaching contributions in the field”.

These included the development of entirely new theories, the most striking of which is now called Hjorth’s theory of turbulence. Dealing with the fundamental nature of complexity and classifiability of mathematical structures, it has had a major impact on contemporary work in set theory and its applications in other areas of mathematics, notably dynamical systems.

Full article here.

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