Gheorghe Ţiţeica (October 4, 1873 in Turnu-Severin – February 5, 1939, Bucharest, publishing as George or Georges Tzitzeica) was a Romanian mathematician with important contributions in geometry. He is recognized as the founder of the Romanian school of differential geometry.
He showed an early interest in science, as well as music and literature. He learned to play the violin when he was young and this remained one of his pleasures throughout his life. He showed his many talents during his years in primary school in Turnu-Severin. By 1885 when he was admitted to the prestigious secondary school "Carol I" National College in Craiova (today named Nicolae Balcescu College) his parents knew that they had a remarkably talented son. In Craiova he continued to achieve top grades, and he also spent time in pursuing his musical interests as a relaxation. The city was a good centre for music and the arts which suited Ţiţeica very well. He graduated from secondary school in Craiova in 1882 and was awarded a scholarship to train to become a teacher at the Training College in Bucharest. He went to Bucharest where, in addition to studying at the Training College, he attended mathematics lectures at the University. Among his lecturers were David Emmanuel, Spiru Haret, O. Gogu, Dimitrie Petrescu and Iacob Lahovary. He graduated with a bachelor's degree in mathematics in June 1895 and in the autumn of that year he began teaching at the theological seminary in Bucharest while continuing his studies for his "capability examination".
He qualified as a secondary school teacher of mathematics in 1896 and later that year was appointed to the "Vasile Alecsandri" secondary school in Galaţi. Teachers at the school, and Ţiţeica's friends, all encouraged him to go to Paris and study further mathematics, and this he did in 1897 when he entered the École Normale Superieure. There he made friends with two other students, Henry Lebesgue and Paul Montel. Among his lecturers were a whole host of leading mathematicians including Darboux, Picard, Poincaré, Appell, Goursat, Hadamard, and Borel. Gheorghe Ţiţeica flourished in Paris having teachers and friends with outstanding mathematical abilities who inspired him to produce excellent research. He published three papers in 1898, namely Sur un theoreme de M Cosserat; Sur les systemes orthogonaux and Sur les systemes cycliques. In the following year he published seven papers including his doctoral dissertation Sur les congruences cycliques et sur les systemes triplement conjugués. His thesis was presented to the Faculty of Science and was examined on 30 June 1899 by a committee headed by Gaston Darboux.
Returning to Romania, Ţiţeica was appointed as an assistant professor at the University of Bucharest where he taught the course on differential and integral calculus. He was promoted to professor of Analytical Geometry at Bucharest University on 4 May 1900. He remained there until his death in 1939. In 1913, at age 40, Ţiţeica was elected as a permanent member of the Romanian Academy, replacing Spiru Haret. Later he was appointed in leading roles: in 1922, vice-president of the scientific section, in 1928, vice-president and in 1929 secretary general. Ţiţeica was also president of the Mathematical Association of Romania, of the Romanian Association of Science and of the Association of the development and the spreading of science. He was a vice-president of the Polytechnics Association of Romania and member of the High Council of Public Teaching. Ţiţeica was elected correspondent of the Association of Sciences of Liège and doctor honoris causa of the University of Warsaw. He was the president of the geometry section at the International Congress of Mathematicians in Toronto (1924), Zürich (1932), and Oslo (1936). In 1926, 1930 and 1937 he gave a series of lectures as titular professor at the Faculty of Sciences in Sorbonne. He also gave many lectures at the University of Brussels (1926) and the University of Rome (1927).
Ţiţeica's research contributions were mainly in geometry, in particular affine differential geometry. The scientific work of Ţiţeica counts about 400 volumes, of which 96 are scientific projects, most addressing problems of differential geometry. Carrying the researches of the American geometer of German origin Ernest Wilczynski, Ţiţeica discovered a new category of surfaces and a new category of curves which now carry his name. He also studied R-networks in n-dimensional space, defined through Laplace equations.
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