**Tibor Gallai** was a Hungarian mathematician who worked in combinatorics and graph theory. He was a friend and collaborator of Paul Erdős.

- Tibor was not born with the name "Gallai" but was actually named Tibor Grünwald.
- We shall call him Gallai throughout this biography but in fact he was known as Tibor Grünwald up to the beginning of World War II.
- The last paper he published under the name Tibor Grünwald appeared in 1939.
- There were two mathematicians in Budapest in the 1930s who were both named Grünwald, namely Tibor Grünwald (the Tibor Gallai of this biography) and Géza Grünwald, but they were not related.
- Géza Grünwald, born 18 October 1910 in Budapest, was 20 months older than Tibor.
- The winner of the high school mathematics competition automatically gained university entry and Gallai (as we will call him) was extremely talented and expected to easily win the June 1930 competition held in his final year at high school.
- Gallai sat the 34th Eötvös Competition in the early autumn of 1930.
- Gallai won the 1930 Eötvös Competition and, as a result, began his university career in Budapest in the autumn of 1930 entering the Pázmány Péter University.
- Gallai began helping Dénes König with his graph theory book, Theorie der endlichen und unendlichen Graphen Ⓣ(Theory of Finite and infinite graphs) which was published in 1936.
- In the book Dénes König mentions results proved by Gallai and also makes use of some of Gallai's ideas.
- This result led to Gallai's first published paper, a joint work with Paul Erdős and Endre Weiszfeld, with title On Eulerian lines in infinite graphs (Hungarian) (1936).
- The first proof though is due to Gallai.
- It first appeared in a paper by Richard Rado (with credit to "Dr G Grünwald", which was Gallai's last name then; the initial "G" should have been "T" and must be a typo).
- More likely Rado was confused between Tibor Grünwald and Géza Grünwald, but of course, it should have been "Dr T Grünwald".
- After the award of his diploma from the Pázmány Péter University, Gallai worked in insurance and in industry until 1939.
- Many Hungarian Jews were called up to serve in labour camps and we assume that this happened to Gallai but we have no details of his wartime experiences.
- The name Tibor Gallai appears on a 1945 "List of all allied Nationals and all other foreigners, German Jews and stateless etc who were temporarily or permanently stationed in the community, but are no longer in residence." This was registering foreigners and German persecutees in the American zone in Bavaria, Germany.
- Certainly when the war ended, Gallai returned to Budapest where he began teaching mathematics in the Jewish High School on Abonyi Street in Budapest.
- But perhaps more importantly, it was Gallai who introduced me to the joy of understanding, of discovering, of the attractiveness of mathematics.
- Gallai became a university professor in 1949 when he was appointed to the Budapest Technical University.
- Gallai, with Rózsa Péter, published a series of mathematics textbooks beginning in 1949.
- Gallai remained at the Budapest Technical University until 1958 when he resigned and became a research worker at the Research Institute of Mathematics of the Hungarian Academy of Sciences.
- We have already mentioned the fact that Gallai taught Vera Sós at the Jewish High School on Abonyi Street in Budapest.
- Gallai was an infinitely pure man.
- Even now, years after his death, he is often referred to at conferences: Gallai was the first to prove this point, but he never published it.
- Needless to say, Gallai was never a rich man.
- Gallai wrote him an official letter in which he complained that the János Bolyai Mathematical Society journal had given such a commendable article about his work that he had, therefore, left the Society in protest.
- Gallai moved to the University of Technology in 1948-49, where he became head of the Department of Mathematics.
- For more than ten years, Gallai had been with her from morning to night, doing everything required for such a disease.
- He always went to Gallai and encouraged him to think about mathematics.
- We have already seen that Gallai was reluctant to publish his results.
- "Gallai was so terribly modest," explained George Szekeres.
- He said that he could not decide which foot to put down first." "Gallai was Paul Erdős's best, closest friend," continued George.

Born 15 July 1912, Budapest, Hungary. Died 2 January 1992, Budapest, Hungary.

View full biography at MacTutor

Origin Hungary

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