Moscow dynamics seminars of the Nineteen seventies and the early career of Yasha Pesin

. This article has an eclectic nature. Its appearance at the beginning of this volume is justified by the personality of the main character. But this is not a scientific biography. My goal was to draw the picture of the milieu which surrounded Pesin and stimulated or obstructed his development as a mathematician, bringing the story to the moment he did his earliest work of great significance and describing reception of this work abroad and at home. Inevitably this slips into the genre of personal recollections, although I also record certain episodes communicated to me by other people, which I either was never aware of or have forgotten. I believe that the crucial element of this milieu was the seminar which D. V. Anosov and I ran throughout most of the nineteen seventies. To put this into a broader perspective I start with a brief description of the mathematics seminar culture at the time and a more detailed discussion of two dynamics seminars: The Sinai–Alexeyev seminar at the Moscow State University and the one mentioned above, with a considerably more space devoted to the latter which from now on I will usually call simply “the seminar”. After this exposition I turn to early stages of Pesin’s career which were practicably inseparable from those of his life-long friend and early collaborator Misha Brin. Then I return to the seminar as a medium when mathematical development of both Brin and Pesin took place. After that my exposition becomes a bit more technical, at least partially: I try to describe the genesis, outline the contents and indicate the importance of two early bodies of work, one joint by Brin and Pesin and the other by Pesin alone. I do maintain another focus on the background and various circumstances of both favorable but primarily unfavorable nature. The last two subsections are again more narrative but they also contain some elements of analysis and illustrations of the impact of Pesin’s work. The 1960s and 1970s were the golden age for dynamical systems 1 in Moscow. The beginning and first flourishing of Yasha’s mathematical career coincides with the second part of this period. He entered the School of Mechanics and Mathematics 2 of the Moscow State University (mech-mat MGU or simply “mech-mat”, as we will call it from now on, following the abbreviated Russian usage) in the fall of 1965,