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Gabriel Andrew Dirac (13 March 1925 – 20 July 1984) was a Hungarian/British mathematician who mainly worked in
graph theory In mathematics, graph theory is the study of ''graphs'', which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of '' vertices'' (also called ''nodes'' or ''points'') which are conn ...
. He served as Erasmus Smith's Professor of Mathematics at
Trinity College Dublin , name_Latin = Collegium Sanctae et Individuae Trinitatis Reginae Elizabethae juxta Dublin , motto = ''Perpetuis futuris temporibus duraturam'' (Latin) , motto_lang = la , motto_English = It will last i ...
1964-1966. In 1952, he gave a sufficient condition for a graph to contain a
Hamiltonian circuit In the mathematical field of graph theory, a Hamiltonian path (or traceable path) is a path in an undirected or directed graph that visits each vertex exactly once. A Hamiltonian cycle (or Hamiltonian circuit) is a cycle that visits each vertex ...
. The previous year, he conjectured that n points in the plane, not all collinear, must span at least \lfloor n/2\rfloor two-point lines, where \lfloor x\rfloor is the largest integer not exceeding x. This conjecture was proven true when n is sufficiently large by
Green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a combin ...
and
Tao ''Tao'' or ''Dao'' is the natural order of the universe, whose character one's intuition must discern to realize the potential for individual wisdom, as conceived in the context of East Asian philosophy, East Asian religions, or any other phil ...
in 2012.


Education

Dirac started his studies at
St John's College, Cambridge St John's College is a Colleges of the University of Cambridge, constituent college of the University of Cambridge founded by the House of Tudor, Tudor matriarch Lady Margaret Beaufort. In constitutional terms, the college is a charitable corpo ...
in 1942, but by 1942 the war saw him serving in the aircraft industry. He received his MA in 1949, and moved to the
University of London The University of London (UoL; abbreviated as Lond or more rarely Londin in post-nominals) is a federal public research university located in London, England, United Kingdom. The university was established by royal charter in 1836 as a degree ...
, getting his Ph.D. "On the Colouring of Graphs: Combinatorial topology of Linear Complexes" there under
Richard Rado Richard Rado FRS (28 April 1906 – 23 December 1989) was a German-born British mathematician whose research concerned combinatorics and graph theory. He was Jewish and left Germany to escape Nazi persecution. He earned two PhDs: in 1933 from th ...
.


Career

Dirac's main academic positions were at the
King's College London King's College London (informally King's or KCL) is a public university, public research university located in London, England. King's was established by royal charter in 1829 under the patronage of George IV of the United Kingdom, King G ...
(1948-1954),
University of Toronto The University of Toronto (UToronto or U of T) is a public research university in Toronto, Ontario, Canada, located on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution ...
(1952-1953),
University of Vienna The University of Vienna (german: Universität Wien) is a public research university located in Vienna, Austria. It was founded by Duke Rudolph IV in 1365 and is the oldest university in the German-speaking world. With its long and rich histo ...
(1954-1958), University of Hamburg (1958-1963),
Trinity College Dublin , name_Latin = Collegium Sanctae et Individuae Trinitatis Reginae Elizabethae juxta Dublin , motto = ''Perpetuis futuris temporibus duraturam'' (Latin) , motto_lang = la , motto_English = It will last i ...
( Erasmus Smith's Professor of Mathematics, 1964-1966), University of Wales at Swansea (1967-1970), and Aarhus University (1970-1984).


Family

He was born Balázs Gábor in
Budapest Budapest (, ; ) is the capital and most populous city of Hungary. It is the ninth-largest city in the European Union by population within city limits and the second-largest city on the Danube river; the city has an estimated population o ...
, to Richárd Balázs, a military officer and businessman, and Margit "Manci" Wigner (sister of
Eugene Wigner Eugene Paul "E. P." Wigner ( hu, Wigner Jenő Pál, ; November 17, 1902 – January 1, 1995) was a Hungarian-American theoretical physicist who also contributed to mathematical physics. He received the Nobel Prize in Physics in 1963 "for his con ...
). When his mother married
Paul Dirac Paul Adrien Maurice Dirac (; 8 August 1902 – 20 October 1984) was an English theoretical physicist who is regarded as one of the most significant physicists of the 20th century. He was the Lucasian Professor of Mathematics at the Univer ...
in 1937, he and his sister resettled in England and were formally adopted, changing their family name to Dirac. He married Rosemari Dirac and they had four children together: Meike, Barbara, Holger and Annette.


See also

*
Dirac's theorem on Hamiltonian cycles In the mathematical field of graph theory, a Hamiltonian path (or traceable path) is a path in an undirected or directed graph that visits each vertex exactly once. A Hamiltonian cycle (or Hamiltonian circuit) is a cycle that visits each vertex ...
* Dirac's theorem on chordal graphs * Dirac's theorem on cycles in -connected graphs


Notes


References

* L. Døvling Andersen, I. Tafteberg Jakobsen, C. Thomassen, B. Toft, and P. Vestergaard (eds.)
''Graph Theory in Memory of G.A. Dirac''
Annals of Discrete Mathematics, volume 41, North-Holland, 1989. . {{DEFAULTSORT:Dirac, Gabriel Andrew 20th-century Hungarian mathematicians Graph theorists Alumni of the University of London 1925 births 1984 deaths Hungarian Jews Paul Dirac Aarhus University faculty Academics of Trinity College Dublin