Do not trust your memory - it is fading

to all my advisers, colleagues, co-authors, and friends

Leonid A. Notov

My school physics teacher in Moscow in 1974-1979 - my luck started in school, Leonid Abramovich is one of the most wonderful teachers I ever met! It is thanks to his ecouragement that I pursued my studies at the university.

Boris I. Zhilinskií

We met when I was a second year student at the Moscow State University. I was in a group specialized in theory and Boris was teaching our problem classes (seminars) in quantum mechanics. He became my Master thesis (diploma) adviser and my unofficial Ph.D. thesis adviser. We have worked together ever since.

Boris introduced me to modern group-theoretical techniques, such as irreducible tensor formalism, and their application in quantum systems with several coupled degrees of freedom, in particular in fine rotation-vibration structure of spherical top molecules, where these methods play a very important role. Later, as he matured himself, he took me with him on the tour of applications of modern topology and invarint theory in the qualitative analysis of classical mechanical systems and their quantum analogues. From the very beginning Boris directed me towards obtaining concrete results that are important theoretically and are useful in the analysis and understanding real systems.

Nikolaí N. Nekhoroshev

1946 - 2008 I met Nikolaí in Dunkerque at the end of 2001 when he took a 6 month invited professor position at our university. He moved to Boulogne-sur-Mer where we spent the New Year's eve together and worked thereafter very intensely up until May 2002.

Kolya worked only in Russian. Normally he was able to say several English phrases without difficulty, but when he was thinking intensely, he could not even pronounce foreign words and it was sometimes difficult to catch up to him. This explains his colorful Russian definitions of new objects which were so difficult to translate! Very sharp and attentive to details, and at the same time, reaching far ahead and widely to other domains that he understood and felt so profoundly, Kolya could iterate painstakingly over and over the same paragraph, lemma, or definition. Sometimes, the result of the whole day spent together amounted to a half-page, and sometimes it was - frustratingly - rejected the next day. It was difficult work, but we succeeded in solving our problem and suggesting something truly new in our field. At the time, with other things piling up, there was no pride or even full appreciation, but now I am looking back with gratitude to the destiny that let me meet and closely work with a mathematician of such level.

It took us several years to write up our proofs of fractional monodromy, and when the work was finally over, we expected Nikolaí to come again in May 2008, and to move together towards new studies. It seemed that we had many years of fruitful collaboration ahead of us. His sudden severe illness one week before his departure put a brutal end to these plans. His many new ideas that he was so eager to discuss with us had never come to light. When I saw him to say farewell in July 2008, he had already lost his sight and had difficulty speaking...

I became involved in preserving the memory of Nikolaí. We tried what we could in the obituary in 2008. In 2016, largely due to the efforts of Alekseí Borisov, the editor of the journal Regular and Chaotic Dynamics, Kolya's last 100-page long manuscript and a volume dedicated to him with several short accompanying texts were published.

Obituary. Uspekhi Mat. Nauk 64/3(387), 174-178 (2009), in Russian
N.N.Nekhoroshev, Monodromy of the fibre with oscillatory singular point of type 1:(-2).
Rus. J. Nonlin. Dyn. 12(3), 413-541 (2016), in Russian
Afterword to the paper by N.N.Nekhoroshev. Rus. J. Nonlin. Dyn. 12(3) 543-555 (2016), in Russian
Foreword to the issue dedicated to the 70-th birthday anniversary of Nikolaí Nekhoroshev. Reg. Chao. Dyn. 6(21) (2016)
D.A.Sadovskií, Nekhoroshev's approach to Hamiltonian monodromy. Reg. Chao. Dyn. 6(21) (2016)

My colleagues at the Herzberg Institute of Astrophysics (HIA)

John Delos

I joined the Atomic Physics group of John after doing a lot of molecular spectroscopy, and I liked the change. John directed me towards learning modern classical mechanics, especially normal forms, and related bifurcation theory. Under his supervision I ventured into areas which were unknown both to him and to me. We were through a lot of hard work, difficult writing and finding common language, and had an eventual success. We had a lot of good time too.

Louis Michel

1923 - 1999 I have met Louis briefly when he came several times to work with Boris in Dunkerque in 1995-98. These were his last years and yet he was full of energy, active and sharp. They used to discuss long hours with Boris and I got involved in practical realizations of some of their ideas on the geometric classification of the perturbed Kepler systems.

Richard Cushman

In the last few years after our first meeting at a workshop in Warwick in 1997, I have been constantly learning from Richard Cushman and am glad to be one of his co-workers. What I appreciate the most in Richard's work is that he presents and studies modern mathematics based on examples of concrete dynamical systems which he considers in great detail. As such his approach is very accessible to physicists and practitioners.

Colleagues of my generation