mathematics

Greg Hjorth

Greg Hjorth is a mathematics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Greg Hjorth rather than just read about it. In short: Greg Hjorth (14 June 1963 – 13 January 2011) was an Australian professor of mathematics and chess player. He worked in the field of mathematical logic.

Key takeaways

Greg Hjorth belongs to mathematics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Greg Hjorth to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Greg Hjorth from memory before moving on to harder problems.

Reference excerpt

Greg Hjorth (14 June 1963 – 13 January 2011) was an Australian professor of mathematics and chess player. He worked in the field of mathematical logic.

Chess career Hjorth came second in the 1980 Australian Chess Championship, at the age of 16. He won the Doeberl Cup in Canberra in 1982, 1985 and 1987, and played for Australia in the Chess Olympiads of 1982, 1984 and 1986. He was Commonwealth Champion in 1983 (joint with Ian Rogers) and International Master in 1984. According to Chessmetrics, his best single performance was at the 1984 British Chess Championship, where he scored 4/7 against 2551-rated opposition, for a performance rating 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, with a dissertation entitled On the influence of second uniform indiscernible. He held faculty positions at the University of California, Los Angeles and the University of Melbourne. The University Of Melbourne awards the Greg Hjorth Memorial Prize (biennial scholarship is awarded to the most outstanding postgraduate thesis in mathematics, with preference given to areas of logic, set theory, measure theory or related topics passed by examiners within the previous two calendar years) named after him. Among his most important contributions to set theory was the so-called theory of turbulence, used in the theory of Borel equivalence relations. In 1998, he was an Invited Speaker of the International Congress of Mathematicians in Berlin.

Death Hjorth died suddenly of a heart attack in Melbourne, on 13 January 2011.

Book G. Hjorth: Classification and Orbit Equivalence Relations, Mathematical Surveys and Monographs, 75, American Mathematical Society, Providence, Rhode Island, 2000.

References

External links Greg Hjorth's webpage at UCLA Greg Hjorth player profile and games at Chessgames.com Chessmetrics Player Profile: Greg Hjorth IM Greg Hjorth interviewed by FM Grant Szuveges

Worked examples

Example 1 — a first encounter with Greg Hjorth

Start with the simplest possible case. Write down what Greg Hjorth claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In mathematics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Greg Hjorth before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Greg Hjorth ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Greg Hjorth

In research: Greg Hjorth appears in mathematics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Greg Hjorth in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Greg Hjorth is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1963 births, 2011 deaths, 20th-century Australian chess players, so understanding it makes those chapters shorter.
In everyday life: Look for Greg Hjorth outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Greg Hjorth in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Greg Hjorth means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Greg Hjorth out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Greg Hjorth in simple terms?

Greg Hjorth (14 June 1963 – 13 January 2011) was an Australian professor of mathematics and chess player. He worked in the field of mathematical logic.

Why does Greg Hjorth matter?

Because it connects several mathematics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Greg Hjorth?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Greg Hjorth.