National Institute of the Republic of Serbia

Đuro Kurepa was born on August 16, 1907 in Majske Poljane in Srpska Krajina as the fourteenth child in his family. He finished elementary and secondary school in Majske Poljane, Glina and Križevci. He got his diploma in theoretical mathematics and physics at the Faculty of philosophy of the University of Zagreb in 1931. Kurepa spent the years 1932-1935 in Paris at the Faculte des Sciences and the College de France. He obtained his doctoral diploma at the Sorbonne in 1935, under supervision of Maurice Frechet. He was on post-doctoral studies at some of the world's best institutions: the University of Warsaw and the University of Paris (1937). After the Second World War he visited Cambridge (Massachusetts), the mathematical departments of the Universities of Chicago, Berkeley and Los Angeles, and the Institute of Advanced Studies in Princeton.

Kurepa's first employment was at the University of Zagreb in 1931, as an assistant in mathematics. He became an assistant professor at the same institution in 1937, associate professor in 1938, and full professor in 1948. He stayed in Zagreb until 1965 when he moved to Belgrade where he was invited to be full professor at the Faculty of Science of the University of Belgrade. He remained there until his retirement in 1977. Meanwhile, he was a visiting professor at Columbia University in New York (Summer School 1959), and Boulder, Colorado, in 1960. Besides the university teaching, Kurepa also worked successfully in organizing scientific work, too, and was very active in administrative matters. He was the founder and president of the Society of Mathematicians and Physicists of Croatia, and president of the Union of Yugoslav Societies of Mathematicians, Physicists and Astronomers. Also, he was the president of the Yugoslav National Committee for Mathematics, as well as the president of the Balkan Mathematical Society. Furthermore, he was the founder and for many years the main editor of the scientific journal *Mathematica Balkanica*, now published in Sofia. Kurepa was also a member of the editorial board of Belgrade's *Publications de llnstitut Mathematique*, and German journal*Zeitschrift fur math-ematische Logik und Grundlagen der Mathematih*.

Professor Kurepa earned many awards, honors and distinctions. He received the highest prize of former Yugoslavia,* the Award of AVNOJ*(1976). He was a full member of SANU, the Academy of Science of Bosnia and Herzegovina, and a corresponding member of JAZU (Yugoslav Academy of Sciences and Arts) in Zagreb. Also, he was a member of the Tesla Memorial Society of the U.S.A. and Canada (1982), and received *the Bernhard Bolzano Charter*, and *the Gramata Marin Drinov* of the Bulgarian Academy of Science (Sofia 1987).

The scientific ouput of Professor Kurepa was tremendous. He published more than 200 scientific papers, and more than 700 writings: books, articles, reviews. His papers were published in journals all around the world, and some of them in the most recognized mathematical journals. Many of his manuscripts were translated into English, French, Italian, and other languages. He delivered scientific talks at many universities of Europe, America and Asia. He participated at dozens of international scientific symposia, and many of them were organized by himself. Professor Kurepa had contacts with many mathematicians from all around the world and thanks to him many of them visited Belgrade. Professor Kurepa was especially proud of his encounter with Nikola Tesla, the great Serbian scientist and engineer, with whom Kurepa was fascinated.

The influence of Professor Kurepa on the development of mathematics in Yugoslavia was immense. At the University of Zagreb he introduced several matheihatical disciplines, mainly concerning the foundations of mathematics and set theory. His work there is best witnessed by the following words fo Sibe Mardešić, a professor of the University of Zagreb:*With his work and influence at the University of Zagreb, particularly introducing modern aspects into mathematics, he gained great benefits for our community.*1 By publishing his doctoral dissertation in extenso in Belgrade's *Pubblications de I Institut Mathematique *in 1935, Kurepa made a first contact with the Belgrade mathematical community. In the beginning of the fifties these contacts became deeper and more frequent. His arrival to Belgrade in the mid-sixties, and the subsequent influence he had on the mathematical community there, may be described with almost the same words. Professor Kurepa exposed the newest results in diverse mathematical disciplines through many seminars, courses and talks. The topics of his lectures were among others: the construction of Cohen forcing, some questions concerning independence results in cardinal and ordinal arithmetic, ordered sets and general topology. He was lecturing in other areas such as analysis, algebra, number theory, and even in computer science. By attending these lectures, many mathematicians gained ideas for their mathematical papers, while graduate students obtained themes for their master and doctoral theses. These works include virtually all doctoral theses of the older generation of topologists, and many algebraists from all over of former Yugoslavia. Many of these mathematicians continued and developed further Kurepa's work.

Kurepa was attracted and gave valuable contributions to many areas in mathematics. He was especially interested in Set Theory, General Topology, Foundations of Mathematics, Number Theory and Algebra. His work includes themes on partially ordered sets, particularly trees, the Continuum Hypothesis, the Principle of Mathematical Induction, cardinal functions in topology, the general theory of uniform and metric spaces, fixed point theorems, the so-called left factorial function, and some problems in matrix theory. Several important mathematical notions carry the name according to him: Kurepa tree, Kurepa hypothesis, Kurepa line, Kurepa space, etc. Only the great scientist deserve such kind of honore.

His bibliography is found here.

Author: Mijajlović, Žarko