**Ennio De Giorgi** was an Italian mathematician who worked on partial differential equations and the foundations of mathematics.

- Ennio attended the "G Palmieri" high school in his home town and showed exceptional talents.
- After graduating from secondary school in 1946 and obtaining his liceo, he travelled to Rome to enter the University there but, given his interests in gadgets, it was the Faculty of Engineering that he entered with the intention of taking a degree in engineering.
- Despite his decision of the topic to study, De Giorgi had already discoved while at school the joy of finding proofs of mathematical theorems which were different from those written in the textbooks.
- For these reasons Picone became one of the great teachers and had many very diverse students, like Fichera, Caccioppoli, and many others, with greatly differing personalities and interests, even in mathematics.
- De Giorgi completed his undergraduate studies in 1950 when he was awarded his laurea.
- But M Picone, a seasoned observer of the development of science, knew how to spot talent; he soon acknowledged E De Giorgi's exceptional abilities.
- De Giorgi attended lectures by Caccioppoli on geometric measure theory, but already by this time he had his own ideas about how to attack problems of minimal surfaces.
- Influenced by methods which Caccioppoli had developed, De Giorgi went on to develop new techniques in geometric measure theory and he applied his results to the calculus of variations proving his regularity theorem for almost all minimal surfaces.
- In 1955 De Giorgi gave an important example which showed nonuniqueness for solutions of the Cauchy problem for partial differential equations of parabolic type whose coefficents satisfy certain regularity conditions.
- In the following year he proved what has become known as "De Giorgi's Theorem" concerning the Hölder continuity of solutions of elliptic partial differential equations of second order.
- From the theorem of Nash one can deduce more or less immediately my theorem, following a quite different line of proof.
- Thus, from my experiences, the discovery of a theorem can be made by different people, as if it were there waiting for someone to uncover it, and the statement of the theorem is always the same.
- In 1958 De Giorgi was appointed to the Chair of Mathematical Analysis at the University of Messina and he took up the appointment in December of that year.
- He held this post for less than a year, however, for he was approached by Alessandro Faedo who persuaded him to move to the Scuola Normale Superiore at Pisa.
- Always cheerful, always available, he enjoyed long debates with his students during which he would toss out original ideas and propose conjectures, or sketching the lines of a proof.
- The authors of this paper are all students of De Giorgi and they describe his contributions to geometric measure theory, the solution of Hilbert's XIXth problem in any dimension, the solution of the nnn-dimensional Plateau problem, the solution of the nnn-dimensional Bernstein problem, some results on partial differential equations in Gevrey spaces, convergence problems for functionals and operators, free boundary problems, semicontinuity and relaxation problems, minimum problems with free discontinuity set, and motion by mean curvature.
- De Giorgi received many honours for his outstanding mathematical contributions including the Caccioppoli Prize in 1960, the National Prize of Accademia dei Lincei from the President of the Italian Republic in 1973, and the Wolf Prize from the President of the Israel Republic in 1990.
- He was also awarded Honoris Causa degrees in Mathematics from the University of Paris in 1983 at a ceremony at the Sorbonne and in Philosophy from the University of Lecce in 1992.
- He was elected to many academies including: the Accademia dei Lincei, the Pontifical Academy of Sciences, the Academy of Sciences of Turin, the Lombard Institute of Science and Letters, the Académie des Sciences in Paris, and the National Academy of Sciences of the United States.
- We should not end this biography without mentioning other aspects of De Giorgi's live.
- There is another aspect of De Giorgi's life that we should mention.
- there is the beautiful article (of the declaration of human rights) about the school which recommends not only tolerance but also understanding and friendship between the various nations and the various religious groups.
- Pure and sentimental tolerance is insufficient; only when united with understanding and friendship does it truly allow human activity to progress.
- In particular, the sciences cannot move forward without understanding and friendship among all scientists.
- From 1988 De Giorgi began to experience health problems.

Born 8 February 1928, Lecce, Puglia, Italy. Died 25 October 1996, Pisa, Italy.

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Origin Italy, Prize Wolf

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive