Gheorghe Țițeica (; 4 October 1873 – 5 February 1939), publishing as George or Georges Tzitzéica, was a Romanian mathematician who made important contributions in geometry. He is recognized as the founder of the Romanian school of differential geometry.
Education
He was born in Turnu Severin, western Oltenia, the son of Anca (née Ciolănescu) and Radu Țiței, originally from Cilibia, in Buzău County. His name was registered as Țițeica–a combination of his parents' surnames. He showed an early interest in science, as well as music and literature. Țițeica was an accomplished violinist, having studied music since childhood: music was to remain his hobby. While studying at the Carol I High School in Craiova, he contributed to the school's magazine, writing the columns on mathematics and studies of literary critique. After graduation in 1892,
Career
Upon his return to Romania, Țițeica was appointed assistant professor at the University of Bucharest. He was promoted to full professor on 3 May 1903, retaining this position until his death in 1939. He also taught mathematics at the Polytechnic University of Bucharest, starting in 1928. In 1913, at age 40, Țițeica 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. Țițeica was also president of the , 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.
His Ph.D. students include Dan Barbilian and Grigore Moisil. Carrying on the researches of the American geometer of German origin Ernest Wilczynski, Țițeica discovered a new class of surfaces and a new class of curves which now carry his name. His contributions represent the beginning of a new chapter in mathematics, namely, affine differential geometry. He also studied webs in n-dimensional space, defined through Laplace equations. He investigated what is now known as the Tzitzeica equation, which was further generalized by Robin Bullough and Roger Dodd (the Tzitzéica–Bullough–Dodd equation).
He is also known for a result on the geometry of circles and triangles in the plane, referred to as Țițeica's , a problem he proposed (and solved) at the ' contest in Galați in 1908. The problem was posed independently by Roger Arthur Johnson in 1916, and the resulting configuration is also referred to as the Johnson circles.
Private life and legacy
thumb|The Țițeica house
thumb|Commemorative plaque
Țițeica married Florence Thierin (1882–1965) and the couple had three children — Radu (1905–1987), Gabriela (1907–1987), and Șerban (1908–1985) — all of whom pursued careers in academia; the youngest one became a renowned quantum physicist. The family lived in a 19th-century house on Dionisie Lupu Street, close to Lahovari Plaza, in Sector 1 of Bucharest; Țițeica moved there around 1913, when he was elected to the academy.
A high school in Drobeta-Turnu Severin and a gymnasium in Craiova bear his name, and so does a street in Sector 2 of Bucharest. The Romanian Academy offers an annual "Gheorghe Țițeica Prize" for achievements in mathematics. The logo of the 40th International Mathematical Olympiad, held in Bucharest in 1999, was inspired by Țițeica's 5 lei coin problem.
In 1961, Poșta Română issued a 1.55 lei stamp in his honor (Scott #1415); he also figures on a 2 lei stamp from 1945 commemorating the founding of Gazeta Matematică in 1895 (Scott #596).