16/07/2026
Gheorghe Calugăreănu (1902 - 1976) was a Romanian mathematician. He is known for his work on complex-valued functions, differential geometry, and algebraic topology. Calugăreănu was born on this day (July 16) in 1902.
Gheorghe Calugăreănu was a natural scientist who went on to serve as rector of the University of Cluj. Gheorghe attended primary school in Bucharest from 1909 to 1913, then the "Ch Lazer" secondary school, also in Bucharest, from 1913 to 1921. After graduating from the famous secondary school, Calugăreănu entered the Faculty of Mathematics and Physics at the University of Cluj. Cluj (known also by its German name, Klausenburg, and its Hungarian name, Kolozsvár) had, with the rest of Transylvania, been incorporated into Romania in 1919, just over a year before Calugăreănu went to study there. The University in Cluj, which had been named the Franz Joseph University since 1881, became a Romanian institution and was officially opened as such by King Ferdinand on 1 February 1920. (The Hungarian university in Cluj moved first to Budapest, then to Szeged.) The university in Cluj was named King Ferdinand I University and it was at this university that Calugăreănu studied from 1921 until 1924.
In 1926 Calugăreănu went to Paris to study at the university there. He was supported financially by a Romanian government scholarship. In Paris he met the leading mathematicians of the day. These included Émile Picard, Jacques Hadamard, Élie Cartan, Paul Montel, Arnaud Denjoy and Gaston Julia. Calugăreănu was awarded a "licence in science" from the University of Paris in 1926, then he was awarded his doctorate in 1928 after submitting his dissertation Sur les fonctions polygènes d'une variable complexe Ⓣ.
After Calugăreănu returned to Romania he worked mainly in Cluj. His first appointment there at the university was in 1930 as an assistant. He was then promoted to a lecturer in 1934 and named professor there in 1942. Over this period there had been changes due to the effects of World War II. In 1940, after the start of World War II, the Hungarian university was moved back from Szeged to Cluj, and the Romanian university in Cluj moved to Sibiu and Timișoara. In 1945, following the end of World War II, the Romanian University returned to Cluj and was named Babeș University (after the Romanian natural scientist Victor Babeș). Parts of the Hungarian university in Cluj moved back to Szeged, while that part which remained in Cluj was named the Bolyai University (after János Bolyai).
Due to the high quality of his teaching and his scientific research, Calugăreănu became one of the most important professors at the University of Cluj. His importance certainly went well beyond the university itself, and he made major contributions to higher education and science throughout Romania. He also held important administrative positions within the university such as Dean of the Faculty of Mathematics from 1953 to 1957. In 1959 the Babeș University and the Bolyai University in Cluj joined to became the Babeș-Bolyai University. Calugăreănu continued to chair the Department of the Theory of Functions at Babeș-Bolyai University.
Calugăreănu worked in a number of different mathematical areas such as the theory of functions of one complex variable, geometry, algebra, and topology. His early work, including the work of his doctoral dissertation, were on the theory of functions of one complex variable and here he particularly extended the work of Dimitrie Pompeiu. His remarkable contributions to the theory of meromorphic functions and univalent functions mean that he is considered as the founder of the school of the geometric theory of univalent functions at Cluj.
In 1963 Calugăreănu published Elements of the theory of functions of a complex variable in Romanian. This elementary textbook covers all the standard topics usually covered in such an elementary text, but also has a chapter on elliptic functions with applications to cubic curves in the plane, and a final section on modular functions which contains the theorem of Picard.
As a lecturer, Calugăreănu gave simple, clear explanations. He spoke quietly and he would start every lecture by spending ten minutes going over the material from the previous lecture. At the end of the lecture he would explain what was coming in the next lecture. This makes it sound as if he would make little progress, but on the contrary, he was able to go steadily though the material. Students really understood the lectures as he gave them and his lectures were models for the highest quality of teaching. His research was elegant and his personality shone through his mathematical papers as it did in his teaching. Some of his results had applications in molecular biology or fluid mechanics. In fact Calugăreănu spoke of about the tension between pure and applied mathematics in his autobiographical paper [2]. He remarks there that, in Communist Romania, the party and the state stress the importance of research which leads to improvements in the conditions of life. However, they also recognize the importance of fundamental research as a foundation for and preliminary to applications. The paper [2] allows us to glimpse other aspects of Calugăreănu's approach to mathematics. He addresses younger mathematicians explaining that because of the rapid expansion in mathematics there is great importance in having a guiding thread or theme in one's research. This, he explains, is especially true if one's work spans several fields. His own work did indeed span several fields, and he recognises that his thread was the idea of invariance which ran through his work in complex variables, differential topology, and modern algebra.
Calugăreănu was elected to the Romanian Academy of Sciences in 1963. His most famous student, Petru T Mocanu the author of [8], was also elected a member of the Romanian Academy of Sciences.
Died
15 November 1976
Cluj, Romania
Source: Mac Tutor
