Jonas Kubilius, a renowned Lithuanian mathematician, made significant contributions to the fields of probability theory and number theory. Throughout his career, he held prestigious positions as a lecturer and professor at institutions such as Vilnius University and the Lithuanian Academy of Sciences. Notably, he served as the rector of Vilnius University for an impressive 32 years. From a young age, Kubilius displayed exceptional intelligence and a passion for learning, particularly in the realms of science and mathematics. Even as a student, he demonstrated remarkable clarity in understanding mathematical concepts and often assisted his peers and teachers in solving complex equations. Despite the challenging political climate in Europe, Kubilius persevered in his studies, successfully completing high school and pursuing higher education at Vilnius University. He furthered his academic journey by obtaining a Doctor of Science degree from the esteemed Steklov Institute of Mathematics in Moscow. Later, he joined the Lithuanian Academy of Sciences, where he dedicated himself to advancing the fields of number theory and probability theory through his scientific research.

## Quick Facts

- Also Known As: Кубилюс, Йонас
- Died At Age: 90
- Mathematicians
- Lithuanian Men
- Died on: October 31, 2011
- Education: Vilnius University, Saint Petersburg State University

## Childhood & Early Life

Jonas Kubilius was born on 27 July 1921 in Fermos village, Eržvilkas county, Jurbarkas district municipality, Lithuania. He was from a family of farmers. He had four younger brothers.

He received his early education from Rudkiškiai grade school and Eržvilkas middle school before enrolling at the Raseiniai high school from where he graduated in 1940. He was a good student and excelled in academics. His favorite subjects were mathematics and literature. He was particularly brilliant in mathematics and even helped his teacher in explaining difficult concepts to his classmates.

He entered the University of Vilnius to study mathematics and graduated summa cum laude in 1946. In between, he had taken a year off to teach mathematics in middle school.

## Career

After receiving his Candidate’s degree, Jonas Kubilius started working at the Institute of Physics and Technology of the Lithuanian Academy of Sciences. He also took up a second part-time teaching position as a lecturer at the university in 1952, simultaneously working at two jobs.

In 1952, he published ‘On some problems of the geometry of prime numbers’ in which he developed the “analytical number-theory in n dimensions” introduced by Hecke and extended the theory with the use of more powerful methods.

By now he had set his eyes on writing a doctoral thesis. He was advised by Linnik to submit his thesis to the USSR Academy of Sciences rather than the Lithuanian Academy. Unable to get into the USSR Academy of Sciences, Jonas Kubilius started working on his doctorate at the Steklov Institute of Mathematics in Moscow and received his Doctor of Science degree (habilitation) in 1957.

During the 1950s, the Vilnius University was going through difficult times. Juozas Bulovas, who became the Rector of the University in 1956, was trying to make the university “Lithuanian” by encouraging the use of the Lithuanian language in place of Russian and to revive the Department of Lithuanian Literature. Bulovas also dismissed some of the poorly performing Soviet staff and re-employed some professors who were returning from their exile in Serbia. But these reforms did not go well with the Soviet authorities and Bulovas was dismissed as the rector.

Jonas Kubilius was offered the position vacated by Bulovas. Initially, he was reluctant to accept it as he was afraid that taking up the role of the rector would interfere with his mathematical research. However, he decided to accept the position as he left that it was his moral duty to take forward the work that Bulovas had so passionately started during his tenure. Thus he became the rector of the university in 1958.

As the rector, he was successful in resisting the pressure to “Russify” the university and promoted the Lithuanian language and culture in the university. He also wrote several textbooks in Lithuanian and encouraged the faculty to write research papers in Lithuanian, English, German, and French along with Russian. He also continued working on his mathematical research. His scientific work was primarily in the areas of number theory and probability theory.

In 1991, he retired from the position of the rector after serving for almost 33 years though he retained his position as a professor in the university.

## Awards & Achievements

He received the Order of the Lithuanian Grand Duke Gediminas, the Lithuanian Presidential Award for his outstanding contribution to the field of mathematics.

## Personal Life & Legacy

Jonas Kubilius was happily married. He deeply loved his wife and the couple shared a happy marriage. They had a son Kestutis who became a mathematician and a daughter Birute who became a professor of medicine.

He lived a long and productive life and breathed his last on 30 October 2011, at the age of 90.

## Trivia

The Turán-Kubilius inequality and the Kubilius model in probabilistic number theory are named after this famous Lithuanian mathematician.