On 14 October, the Joint Institute for Nuclear Research pays tribute to Academician Alexei Norairovich Sissakian (1944 – 2010), the JINR Director in 2005 – 2010, a great scientist in the fields of elementary particle physics, theoretical and mathematical physics.

Alexei Sissakian was born in a family of scientists in Moscow. His father Norair Martirosovich Sissakian was an outstanding biochemist, one of the founders of space biology and medicine.

After his graduation from the Faculty of Physics of Moscow State University (MSU) in 1968, the whole career of Alexei Sissakian turned out to be connected with the Joint Institute for Nuclear Research. Having joined the Laboratory of Theoretical Physics JINR, he worked his way up from a trainee researcher to the head of the sector. From 1979 to 1989, Sissakian was Chief Scientific Secretary of the Institute. From 1989 to 2005, he was JINR Deputy Director. Since 2033, he was Director of the Laboratory of Theoretical Physics. In 2006, he was elected Director of the Joint Institute for Nuclear Research.

Alexei Sissakian’s research interests covered the fields of phenomenology of the mass production of elementary particles in high energy collisions, approximate problem-solving methods of quantum field theory and quark-gluon plasma physics. He is the author of more than 400 scientific papers on theoretical and mathematical physics, phenomenology of elementary particles, and relativistic nuclear physics, five books, and five inventions.

Alexei Sissakian in collaboration with a group of scientists developed a method of continual integration in quantum field theory, namely the straight-line path approximation. They also offered a description of elementary processes with large momentum transfers. These studies made it possible to predict a number of effects in experiments at accelerators during mass particle production.

Together with other theoretical scientists, Sissakian conducted classical and quantum superintegrable systems in the constant curvature space. Under the guidance of Alexei Norairovich, a series of studies on the generation of topologically nontrivial objects in models with oscillatory interaction and in supersymmetric one-dimensional quantum mechanics was written. In recent years, Alexei Sissakian togerther with his colleagues developed the method of contraction of Lie algebras applicable for theoretical physics problems.

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Scientific papers by Alexei Sissakian and his group dedicated to the development of methods of quantum field theory beyond the perturbation theory were published. He studied individual mechanisms of the production of quark-gluon plasma in the collision of heavy ions accelerated to high energies.

It was Alexei Norairovich Sissakian who was the ideologist and the first leader of the NICA Megascience Project at JINR, the heavy ion accelerator complex.

Academician Sissakian took part in the preparation of scientific programmes and data processing of a number of experimental collaborations at the world’s leading scientific centres: DELPHI at the LEP accelerator and ATLAS at CERN, CDF (FNAL), etc.

Alexei Sissakian was a member of several Russian and foreign academies of sciences. In particular, he was a member of the RAS Presidium and first Deputy Chairman of the Russian Pugwash Committee. Being President of the Union of Russian Science Cities, he was a member of the Commission on Particles and Fields of the International Union of Pure and Applied Physics, International and European Committees for Future Accelerators, the Scientific and Technical Council of the Ministry of Atomic Industry of the Russian Federation and Rosatom. Moreover, Alexei Sissakian was the organizer of many international conferences and scientific schools, Co-chairman of the CERN-JINR Cooperation Committee, a member of the editorial boards of several scientific publications, Deputy Editor-in-chief of the journal “Physics Particles and Nuclei”, Editor-in-chief of the journal “Physics of Particles and Nuclei, Letters”. He put a lot of effort in training of young scientists. Since 1989, he was a professor and Head of faculties at such leading universities as MSU, MIPT, MEPhI, MIREA, he also was Vice-President of Dubna State University. Under the guidance of the scientist, more than 10 dissertations were defended. He headed the scientific seminar “Symmetries and Integrable Systems” at BLTP JINR.

“He did a lot to organize and support scientific research at our Institute and its Member States, made a significant contribution to the development of international scientific cooperation,” Vladimir G. Kadyshevsky, another JINR Director, remembered about Sissakian. Moreover, Vladimir Kadyshevsky noticed such personal traits of his friend as generosity, kindness and attention to others, he was always ready to help in difficult situations. “Talking about the period when Alexei Norairovich headed JINR, I can say that the Institute got a second wind during those 5 years,” Academician Kadyshevsky wrote.

It should be noted that Alexei Norairovich was fond of poetry throughout his life. He is the author of five poetry collections full of sincere emotions, original thoughts, and lyricism.

Alexei Norairovich Sissakian was awarded the Lenin Komsomol Prize in Science and Technology, Order “For Merit to the Fatherland” IV class, the Orders of Honour and Friendship of the Russian Federation, and other Russian and foreign awards. A street at the right-bank site of the Dubna Special Economic Zone was named after Alexei Sissakian.