Remembrance of a colleague - Khimuri Rukhaia 75

Professor Khimuri Rukhaia, one of the prominent representatives of the Georgian School of Mathematical Logic - Doctor of Science, passed away on April 28, 2020 after a long illness.

2021 year marks 75 years since Khimuri Rukhaia's birth, and we, his students and colleagues, had duty to honor the vivid memory of this highly successful scientist, excellent teacher and noble person. In addition to all this, Khimuri Rukhaia also remembered by the Georgian Mathematical Society because of his outstanding devotion, decency and kindness, which, on the whole, was a direct reason why the thematic section of the XI International Conference of the Georgian Mathematical Union "Logic, Language, Artificial Intelligence" was dedicated to his vivid memory.

Khimuri Rukhaia was born on October 5, 1946, in Martvili, Georgia, in a family of teachers. His father, Mikheil Rukhaia, was an honored teacher, director of the Akhali Kindghi village secondary school in the Ochamchire district, and chairman of the village council executive committee at various times. His mother, Nino Kutsia, also an honored teacher, worked at the school for almost half a century, and for some time was also the deputy director.

Khimuri Rukhaia graduated from the high school in the village of Akhali Kindghi in the Ochamchire district in 1963 and in the same year enrolled at the Faculty of Mechanics and Mathematics of the Ivane Javakhishvili Tbilisi State University. After successfully graduating from the University in 1968, he worked for the rest of his life at the Ilia Vekua Institute of Applied Mathematics in various scientific positions, including head of the Laboratory of Applied Logic and Programming and head of the Department of Mathematical Logic and Methodology. In 1974-75 he was a guest researcher at the Institute of Mathematics at the University of Warsaw.

Khimuri Rukhaia successfully defended his dissertation on "About the System of Contracting Symbols" at Leningrad State University in 1980 under the supervision of his teacher, founder of the school of classical mathematical logic in Georgia, Professor Shalva Pkhakadze. In 1986, the USSR Higher Certification Commission awarded him the title of Senior Researcher, specializing in Mathematical Logic, Algebra and Number Theory.

Khimuri Rukhaia's research interests were classical and computational logic. He has published about 100 scientific articles and five textbooks in this field and is the author of six patented inventions. His research essentially uses the principle of constructing mathematical-type formal theories developed within the framework of notation theory by his scientific supervisor Shalva Pkhakadze, which is very productive and led to a number of important results.

Khimuri Rukhaia often participated in local and international conferences. He had close professional contacts with Georgian and foreign colleagues. He organized many scientific conferences, symposiums and seasonal schools in Georgia. Among them are the All-Union Conferences in Mathematical Logic and the annual international symposium "Language, Logic and Computation", which has been held regularly since 1995 with the participation of many famous scientists in these fields.

Since 2004, Khimuri Rukhaia, together with his Austrian and French colleagues, has been organizing the Tbilisi International Summer School "Language and Logic" every year, where lectures have been given by invited scholars from leading Western universities. The events organized by him have always been of a high standard and have rised great interest in international and local scientific communities, as well as among students.

In parallel with his scientific and organizational activities, Khimur Rukhaia has been teaching since 1976 at Ivane Javakhishvili Tbilisi State University, and since 1985 at Sokhumi State University, where he has been an associate professor since 2006. Under his supervision, seven doctoral students at Tbilisi and Sokhumi State Universities successfully defended their doctoral degrees. They are: Konstantine Pkhakadze, Lali Tibua, Tsiala Dzidziguri, Mzia Patsatsia, Temur Ormotsadze, Mzia Talakhadze, and Nana Pipia.

Khimuri Rukhaia paved the way for many young people in science, connected them with colleagues in different parts of the world, trained them, helped them, and shared his rich experience with them. His greatest merit is that many of his students did not loose the interest in research even during the difficult years and later became successful scientists.

Khimuri Rukhaia was not only a good scientist and teacher, but also an exemplary family man. He always acted according to the principle that "the new generation should be better than the old one" to his students and children. In this regard, it is necessarily noteworthy that Khimuri Rukhaia together with his wife - Christine Jmukhadze, raised four children, who proudly continue the family tradition:

The eldest daughter, Nino Rukhaia-Mosemghvdlishvili, Doctor of Economics, has been working at the David Aghmashenebeli National Defence Academy since 2014, for which in 2021 she was awarded the III degree medal for "Impeccable Service".

Mikheil Rukhaia (Junior), Doctor of Computer Science, followed in his father's footsteps and is currently the head of the Laboratory of Applied Logic and Programming and chief researcher at the Ilia Vekua Institute of Applied Mathematics.

Giorgi Rukhaia, a researcher at the French Institute for Research in Computer Science and Automation (INRIA), is currently working on his doctoral dissertation in mathematics under the ROMSOC grant from Maria Curie of the European Union.

Vakhtang Rukhaia is a second-year undergraduate student in Sociology at Tbilisi State University, Faculty of Social and Political Sciences.

It has been a year since Khimuri Rukhaia is in the kingdom of heaven. We are sure that he will always remain as a symbol of honesty, kindness, professionalism, being remembered as an excellent colleague, teacher and a warm, reliable friend.

Lali Tibua - Researcher at Ilia Vekua Institute of Applied Mathematics, Ivane Javakhishvili Tbilisi State University

Besik Dundua - Researcher at Ilia Vekua Institute of Applied Mathematics, Ivane Javakhishvili Tbilisi State University

Konstantine Pkhakadze - Director of the Georgian Technical University Center for Cultural Protection and Technological Development of Georgian State Languages, Member of State Language Expert Commission

Temur Kutsia - Associate Professor at Research Institute for Symbolic Computation, Johannes Kepler University Linz, Austria