Greg Hjorth (14 June 1963 – 13 January 2011) was an Australian Professor of Mathematics,

chess Chess is a board game for two players, called White and Black, each controlling an army of chess pieces in their color, with the objective to checkmate the opponent's king. It is sometimes called international chess or Western chess to dist ...

International Master (1984) and joint (with Ian Rogers) Commonwealth Champion in 1983. He worked in the field of

mathematical logic Mathematical logic is the study of formal logic within mathematics. Major subareas include model theory, proof theory, set theory, and recursion theory. Research in mathematical logic commonly addresses the mathematical properties of formal ...

Chess career

Hjorth came second in the 1980

Australian Chess Championship The Australian Chess Championship is a tournament organised by the Australian Chess Federation and held every two years. The tournament is largely restricted to Australian chess players, although it is common to allow a small number of strong overse ...

, at the age of 16. He won the

Doeberl Cup The Doeberl Cup is an annual chess tournament held in Canberra, Australia. It has been held every year since 1963 (apart from 2020) and is the longest running weekend chess event in Australia. Since its inception the event has grown both larger and ...

in Canberra in 1982, 1985 and 1987, and played for Australia in the

Chess Olympiad The Chess Olympiad is a biennial chess tournament in which teams representing nations of the world compete. FIDE organises the tournament and selects the host nation. Amidst the COVID-19 pandemic, FIDE held an Online Chess Olympiad in 2020 an ...

s of 1982, 1984 and 1986. According to

Chessmetrics Chessmetrics is a system for rating chess players devised by Jeff Sonas. It is intended as an improvement over the Elo rating system. Implementation Chessmetrics is a weighted average of past performance. The score considers a player's win percen ...

, his best single performance was at the 1984

British Chess Championship The British Chess Championships are organised by the English Chess Federation. The main tournament incorporates the British Championship, the English Chess Championships and the British Women's Chess Championship so it is possible, although it has ...

, where he scored 4/7 against 2551-rated opposition, for a

performance rating The PR (Performance Rating, P-rating) system was a figure of merit developed by AMD, Cyrix, IBM Microelectronics and SGS-Thomson in the mid-1990s (Cyrix announced it in February 1996) as a method of comparing their x86 processors to those of r ...

of 2570. Hjorth retired from most chess in the 1980s.

Mathematical career

Hjorth earned his PhD in 1993, under the direction of

W. Hugh Woodin William Hugh Woodin (born April 23, 1955) is an American mathematician and set theorist at Harvard University. He has made many notable contributions to the theory of inner models and determinacy. A type of large cardinals, the Woodin cardinals, ...

, with a dissertation entitled ''On the influence of second uniform indiscernible''. He held faculty positions at the

University of California, Los Angeles The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California S ...

and the

University of Melbourne The University of Melbourne is a public research university located in Melbourne, Australia. Founded in 1853, it is Australia's second oldest university and the oldest in Victoria. Its main campus is located in Parkville, an inner suburb no ...

. Among his most important contributions to

set theory Set theory is the branch of mathematical logic that studies sets, which can be informally described as collections of objects. Although objects of any kind can be collected into a set, set theory, as a branch of mathematics, is mostly conce ...

was the so-called theory of ''turbulence'', used in the theory of

Borel equivalence relation In mathematics, a Borel equivalence relation on a Polish space ''X'' is an equivalence relation on ''X'' that is a Borel subset of ''X'' × ''X'' (in the product topology). Formal definition Given Borel equivalence relations ''E'' and '' ...

s. In 1998 he was an Invited Speaker of the International Congress of Mathematicians in Berlin.

Death

Hjorth died of a

heart attack A myocardial infarction (MI), commonly known as a heart attack, occurs when blood flow decreases or stops to the coronary artery of the heart, causing damage to the heart muscle. The most common symptom is chest pain or discomfort which ma ...

in Melbourne, on 13 January 2011.

Book

*G. Hjorth: ''Classification and Orbit Equivalence Relations'', Mathematical Surveys and Monographs, 75,

American Mathematical Society The American Mathematical Society (AMS) is an association of professional mathematicians dedicated to the interests of mathematical research and scholarship, and serves the national and international community through its publications, meetings, ...

, Providence, Rhode Island, 2000.

References

External links

Greg Hjorth's webpage at UCLA
*
Chessmetrics Player Profile: Greg HjorthIM Greg Hjorth interviewed by FM Grant Szuveges
1963 births 2011 deaths Set theorists Mathematicians from Melbourne Australian chess players Chess International Masters Chess Olympiad competitors University of California, Los Angeles faculty Mathematical logicians Tarski lecturers {{Australia-chess-bio-stub