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Sergey Vsevolodovich Yablonskiy

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Sergey Vsevolodovich Yablonskiy – Soviet mathematician, one of the pioneers and founders of the soviet scientific school of mathematical cybernetics. Yablonskiy was one of the most active followers of A.A. Lyapunov. He participated in all Lyapunov's cybernetic seminars, which created scientific basis for that new science. Yablonskiy himself was a leading expert in discrete mathematics and mathematical cybernetics – he published number of classical works on problems of synthesis, reliability and control systems monitoring.

Sergey Vsevolodovich Yablonskiy

Sergey Vsevolodovich Yablonskiy

In 1950 he graduated from the Moscow State University (MSU), where remained as a scientific collaborator. Since 1953 he also worked at the ‘V.A. Steklov Institute of Applied Mathematics[1]' (one of the most important mathematical institutions in the USSR). In 1963 he received a professorship at the MSU, since 1968 was a corresponding member of the USSR Academy of Sciences. In 1971 Yablonskiy founded the chair “Theory of Automata and Mathematical Logic” at the MSU (later re-named into chair of “Mathematical Cybernetics”) and held it until his last day.

He was awarded the “Lenin Premium” and decorated with several orders for his scientific contribution and also for army service during the war (WWII).

S.V. Yablonskiy was born on the 6 th of December 1924 in Moscow. His father was a student of the MSU. Later he became a professor of mechanics at the Moscow Institute of Oil industry. The young family was by no means rich but the cultural level was high (what was quite common that time). They lived in a typical Moscow community of several families that shared a big flat of six rooms. Sergey did not have much toys but possessed a vivid fantasy and was interested in reading fantastic literature by Herbert Wales and Julius Verne. He loved to play scenes from those books together with other –numerous – children of their flat. Sergey never had interest to geography or history, but quickly mastered chess (however equally quickly abandoned it). Later he organised at home “scientific society” of his school friends, where they regularly discussed new scientific problems, made reports and even published a home made satirical magazine (what once caused a scandal with danger of serious, even political, consequences which he escaped only by lucky chance).

The family lived in the building next to the mathematical department of the MSU (in the centre of the city) – that was the reason for the joke, that his future mathematical career was predetermined. Anyway, his mathematical talents emerged already at the school years – in 1940 he became the winner of the 6 th Moscow Mathematical Olympiad among schools, what was very important event at that time. The brother of S.V. Yablonskiy remembered that Sergey also was lucky to have a brilliant teacher of mathematics at school (N 545). That was Isaak Lvovich Agranovich, who managed to develop interest to mathematics almost in every pupil. However, the meeting and friendship with famous mathematician – Aleksey Andreevich Lyapunov (1911-1973) was one of the most important events in his life.

A.A. Lyapunov lived within a half-kilometer from the Yablonskiys. He had his own family, loved children and paid much attention to their education. Lyapunov, who was very intellectual person, founded mathematical work-group at the school 545, where he soon noticed abilities of Sergey Yablonskiy. Sergey became his pupil-friend and spent much time at the Lyapunov's. Outside mathematics Lyapunov was interested in genetics (what was officially “not welcomed” then). Friendship with Lyapunov made profound influence on the whole future scientific life of Sergey and also helped to form his determinate and solid personality.

Having finished school he entered the faculty of mechanics and mathematics of the MSU but could study just a short time. It was the year 1941, the war broke out. He visited university, participated in building of the Moscow defence constructions and also worked as a post-man. As soon as he was 18 (in 1942) Yablonskiy joined the army (a tank brigade, where he was a radio-master) and served there until the Victory Day. He was lucky to escape any serious harm, however, two orders “Patriotic War”, two orders “Combat Red Banner[2]”, an order “Glory” and medals could be good evidence of his gallantry.

On his return to the university in 1945 he actively took to learning and successfully graduated in 1950. Professor Nina Karlovna Bari[3], famous for her works on Theory of Series and on mathematical logic, was his scientific supervisor during that time.

After demobilisation Jablonskiy continued friendship with Lyapunov, who also was a veteran of war. He was teaching mathematics at the Artillery Academy in Moscow . The post-war atmosphere at the universities was very enthusiastic: young people returning from army had an “enormous hunger for knowledge” and were ready to study “day and night”. Lyapunov – a refined intellectual for whom science was “natural way of life”, was convinced that knowing of mathematics was not only a professional matter, but also the basis of scientific culture in general. Thus in addition to the academic curriculum Lyapunov founded regular scientific seminar at his own home. It was very popular among his students who steadily attended it since the beginning – in 1948- until it was transferred to the MSU – in 1953. Both the extended mathematical course and most actual scientific ideas and news were studied and discussed there.

Lyapunov's seminar became the place where young people first learned about the science “Cybernetics” and approached its problems. Now Lyapunov is recognised by the world's scientific society as a pioneer and one of the founders of the Soviet cybernetics. His students – the seminar members – S.V. Jablonskiy and N.P. Buslenko (from the MSU), A.I. Kitov, I.V. Poletaev (from the Artillery Academy) and some others were his most active collaborators and later became leading cyberneticists themselves.

In 1950 Yablonskiy published his first scientific work, “About Concurrent Sequences of Continuous Functions”. At the same year he entered department of postgraduate education at the faculty of mechanics and mathematics, where Petr Sergeevich Novikov[4] was his scientific supervisor and eventually a decisive influence on his scientific work. Novikov had been also a tutor, supervisor and “elder friend” of A.A. Lyapunov, what naturally helped them to find the ‘common scientific language'.

Yablonskiy concentrated his research on problems of expressibility in mathematical logic. His work demonstrated that those problems, being a product of mathematical logic, would find more adequate description and solution if they were considered from positions of the discrete multi-valued functions theory. Development of the theory and solution of certain concrete problems with its methods (final solution of the problem of comprehensiveness in 3-value logic was among them) composed basis of his dissertation thesis, “Problems of functional comprehensiveness in k-value calculus”, successfully submitted in 1953.

In the same 1953 Yablonskiy received position at the department of applied mathematics of the Steklov Mathematical Institute (in Moscow). Lyapunov also collaborated with that institute and Novikov was appointed as the first head of the Department of Mathematical Logic there, in 1957. Yablonskiy continued his research on discrete multi-valued functions and in 1958 published fundamental review, “Functional Schemes (formations) in k-valued Logic[5]”, in which he efficiently summarised the knowledge on the subject accumulated by that time. The article subsequently played important role in further development of discrete mathematics and forming of mathematical cybernetics, and during years served as a fundamental courseware for students of the theory of discrete functions. Yablonskiy also actively researched problems of synthesis of logical devices. Some important works on electrical circuits testing (S.V. Yablonskiy, I.A. Chegis, et. al.) were performed. Their article “Logical Means of Electric Circuits Operation Control” was published in the same “volume 51” of “Trudy MIAN”. It made notable impact on development of logical combinatory methods both in theory of circuit reliability and in image recognition.

Mathematical researches and close contacts with Lyapunov and other progressive scientists involved Jablonskiy into the famous “struggle for cybernetics”. Its beginning phase was marked with fierce criticism form many officious ideologists of that time. Lyapunov, Yablonskiy, Kitov were in avant-garde of its propagators. In 1954-1964 Lyapunov invited him to cooperate in establishing and conducting a regular cybernetics seminar at the MSU. That was famous “Big Seminar on Programming” – the first official regular scientific activity on cybernetics problems in the USSR. To fully realise its scientific, and also social, meaning one shouldn't forget that in the first half of the 1950-s the subject of cybernetics was condemned by official philosophers as the most “heretical issue” – a “false science” (luckily that was mainly on polemical level; “information” about brutal repressions against its supporters is mainly exaggeration). However, in 1964, when the seminar was closed because Lyapunov moved to Novosibirsk to work at the new -Siberian- branch of the Academy, it was by and large established, highly popular science. In 1958 Lyapunov organised regular publication of collection of works “Problems of Cybernetics”, where Jablonskiy and others took active part on all stages.

As mathematician Yablonskiy realised importance of purely mathematical problems in cybernetics domain and their separation from philosophy and ideology. In 1959 he published a summary of his analysis in the “Problems of Cybernetics”, titled “Basic Notions of Cybernetics”. The article presented mathematically formalised notion of controlling systems, displayed the problems and predicted ways of development of the controlling systems theory. He made essential contribution to popularisation and propagation of the cybernetic ideas. His reports, prepared in collaboration with A.A. Lyapunov, A.I. Kitov and I.A. Poletaev, were presented at the third (1956) and fourth All-Union Mathematical Congresses, at the international congress of IFIP on information processing (1968) and at some other conferences. His publications on theoretical and applied problems of cybernetics also appeared in periodical on maritime engineering, “Maritime Collection”. The latter was possible due to active assistance of admiral and academician Aksel (Axel) Ivanovich Berg – then the USSR vice minister of defence. He was most devoted, most practical –and influential – promoter of the new science. It was Axel Berg who established the first official scientific organisation on cybernetics, and headed it during the next twenty years.

In 1960 he also made publication together with A.A. Lyapunov and A.I. Berg, in 1961 together with Lyapunov published an article at the Institute of the World Economy and International Relations, in 1963 Lyapunov and Yablonskiy made one more publication in the “Problems of Cybernetics”.

In 1958 Yablonsky became the head of the department of mathematical cybernetics, which he created together with Lyapunov at the Institute of Applied Mathematics . There he performed researches on the problems of complexity of algorithms for schemata minimisation. Results of the work explained difficulties in creation of minimised schemas, they were utilised in his dissertation, “About some Mathematical Problems in the Theory of Control Systems”, which he successfully submitted in 1962 and was awarded a doctorate.

In 1966 he, Y.I. Zhuravlev and O.B. Lupanov were awarded “Lenin Premium” for complex of works on theory of control systems. In 1968 he was elected a corresponding member of the Academy of Sciences USSR (department of mathematics), where he actively worked as the second academic secretary. Yablonskiy was also one of the founders (and a member) of the Academy of Cryptology where he was equally active.

He also was always interested in discrete methods for the control systems theory and insisted on development of various items of discrete mathematics as the basis of building and analysis of discrete models in their various applications. Therefore he performed a big work on strengthening coordination between the mathematical cybernetics and discrete mathematics and information exchange between the both to provide most favourable conditions for researches in the both fields. Continuing traditions of the “big programming seminar”, closed in 1964, Yablonskiy established another seminar on mathematical problems of cybernetics, which he regularly conducted at the MSU, on Fridays, during more than thirty years. It is still working under guidance of his former student Oleg Borisovich Lupanov, now academician of the Russian Academy of Sciences. The seminar was naturally focused on mathematical cybernetics and discrete mathematics. It was visited not only by scientists of Moscow but also by guests of other towns and countries - in traditions of the “Big Seminar”. Invitation to make a report at the seminar was itself always a sign of higher estimation of the participant's achievements.

Yablonskiy took active part in organisation of the first All-Union theoretical conferences on cybernetic problems, and was chairman of its Organisational Committee many following years. He himself did a lot to establish and support scientific cybernetic centres and their activity not only in Moscow but equally in other various towns of Russia , such as Nizhniy Novgorod (Gorkiy), Kazan , Saratov , Novosibirsk , Irkutsk , etc. His book “Functions of Algebra of logic and Post Classes”, published jointly with his students G.P. Gavrilov and V.B. Kudryavtsev in 1966, played notable role in popularisation of the discrete functions theory.

Since 1974 (soon after the death of A.A. Lyapunov) Yablonskiy became the editor in chief of the journals (collections of works) “Problems of Cybernetics” (since 1989 they are named “Mathematical Problems of Cybernetics”). He also actively worked on “Mathematical Encyclopaedia“, on its section dealing with problems of discrete mathematics and mathematical cybernetics. Together with O.B. Lupanov he prepared the famous collection of articles “Discrete Mathematics and Mathematical Problems of the Cybernetics”. His numerous scientific works in that field were translated into many languages and made an essential influence on contemporary mathematics.

Beisdes his scientific researches Yablonskiy paid big attention to education. When he was working at the Institute of Applied Mathematics he also lectured at the department of mechanics and mathematics of the MSU, since 1954. He established and held –experimental- courses “Introduction into Discrete Mathematics” and “Fundamentals of Cybernetics”. In 1963 he was awarded a professorship at the MSU. In 1970 he participated in organisation of the MSU new department “Computation Mathematics and Cybernetics” (CMaC). In 1971 he founded –and headed – the MSU chair, “Theory of Automata and Mathematical Logic”, re-named into “Mathematical Cybernetics” soon after. He held it practically till his last days.

At the CMaC Yablonskiy integrated his cybernetic courses into curriculum so that they became obligatory discipline. He developed the content and subsequently it formed solid basis for special university course “Discrete Mathematics”, utilised by all Soviet universities. His course-book “Introduction into Discrete Mathematics” – published in 1979 and re-published in 1986- remains the basic university courseware in Russia and some other countries. He also organised series of All-Union methodical conferences, where problems of lecturing on discrete mathematics were the core issue. Yablonskiy published his works in many scientific journals and himself was a member of the journal “Discrete Mathematics” board.

Yablonskiy taught hundreds of students and supervised 25 dissertation researches for the “Candidate of Sciences” degree. His seminars attracted numerous scientists including professors and members of various academies. Several generations of his students from several countries formed and continued the powerful scientific school created by him. He himself was a member of several councils –including the USSR Highest Attestation Committee on dissertations and awarding scientific degrees.

Yablonskiy also actively participated in establishing of the Stefan Banach[6] International Mathematical Centre. For a long time he was a member of the centre's council and regularly organised there semesters on discrete mathematics.

Yablonskiy possessed very dutiful and solid character and firm principles. As a person he was characterised with attentive and friendly attitude to other people. He had a born talent of understanding new ideas.

His scientific and pedagogical contributions were eventually appreciated by governmental administration; he was decorated with the order “Red Banner of Labour”.

S.V. Yablonskiy lived all his life in Moscow . He died in 1998.


1. More on “Steklov Mathematical Institute” (also called MIAN – Matematicheskiy Institut Academii Nauk ) see in biography of I.Y. Akushskiy:

2. There is also the other “Red Banner” – civil order “Red Banner of Labour”.

3.Nina Karlovna Bari:

4.Petr Sergeevich Novikov -

5. Published in “Trudy matematicheskogo instituta im. V.A. Steklova ” vol.51 Moscow 1958.

6.Stefan Banach – famous Polish mathematician; full biography:


  1. Virtual Computer Museum”: Russian biography of S.V. Yablonskiy by V.B. Alekseev, and biographical notices by his brother E.V. Yablonskiy.
Started by Eduard Proydakov in 1997
© Russian Virtual Computer Museum, 1997-2021