John Hazzidakis

Ioannis "John" N. Hazzidakis (Ιωάννης Χατζιδάκις, or Hatzidakis or Chatzidakis, 1844 – 1921) was a Greek mathematician, known for the Hazzidakis transform in differential geometry. The Hazzidakis formula for the Hazzidakis transform can be applied in proving Hilbert's theorem on negative curvature, stating that hyperbolic geometry does not have a model in 3-dimensional Euclidean space.

He was born in Crete in 1844. He completed his basic education in Syros and from 1863 he studied mathematics at the National and Kapodistrian University of Athens. He graduated with a Ph.D. in Mathematics in 1868 and went on a scholarship from the University in Paris and Berlin to continue his studies. He was a student of the Paris school of differential geometry and of Karl Weierstrass in Berlin.

He returned to Greece and was appointed a lecturer in 1880 and then a professor ordinarius in 1884, retiring in 1914 as professor emeritus of mathematics at the University of Athens. He also taught theoretical mechanics at the National Technical University of Athens (1888–1914) and mathematics at the Academy of Sciences (1873–1900) and the Naval Academy of Sciences (1886–1891). At the University of Athens, he was Dean of the Faculty of Philosophy for the academic year 1890-1891, Dean of the School of Sciences for the academic year 1904–1905, and Dean of the School of Philosophy for the academic year 1911–1912. He died in 1921.

He was the father of the linguist Georgios Hatzidakis and the mathematician Nikolaos Hatzidakis.

According to William Caspar Graustein, a mathematical statement first made by Louis Raffy was published in 1893 with an erroneous proof; Hazzidakis gave a valid proof of the statement in 1897.

Hazzidakis wrote numerous research and pedagogical works, among the latter are:

The articles of Ιωάννης Χατζιδάκις published in German appeared under the name "J. N. Hazzidakis".

...
Wikipedia