The co-author of the “bible” for physicists Lev Pitaevsky passed away

It is very difficult to say what benefit theoretical physicists bring, because the timeframe for obtaining a practical result from their work can be quite remote. For example, 37 (!) years have passed since 1917, when Rutherford observed the first nuclear reaction, and until the creation of the first peaceful development – a nuclear power plant in Obninsk. And this is not much yet – it happens that it takes half a century or even more to wait for the moment when reality catches up with theory.

Lev Petrovich Pitaevsky was one of the iconic theorists of our time, a student of the famous Lev Landau. He made many discoveries in low temperature physics, plasma physics, quantum mechanics, macroscopic electrodynamics, metal theory…

It makes no sense to delve into the essence of his works devoted to “Bose-Einstein condensation” or “the theory of solitons”, anyway, we will understand little of them. However, the many awards he received in different years speaks of the unconditional significance of this scientist.

The importance of Lev Pitaevsky’s contribution to science and pedagogy is difficult to put into words. He developed the theory of quantum crystals, the fundamental issues of the transition of liquid helium-3 to a superfluid state at sufficiently low temperatures.

His enduring contribution also, of course, consists in the fact that he completed the materials of the famous ten-volume book by Lev Landau “Course of Theoretical Physics”. As you know, Pitaevsky’s teacher did not have time to finish the work of his life, leaving us early enough. In fact, Pitaevsky completed the materials for three volumes of this course. And the whole world is still learning from this textbook! It’s like the bible for physicists.

Many have heard of helium-3 due to the fact that it is going to be mined on the moon. This is a unique fuel for safe thermonuclear reactions, but this is far from its only possible application. With regard to matter, Pitaevsky was not interested in ultra-high temperatures, but, on the contrary, in ultra-low ones. And his work made a fundamental contribution to the theory of the physics of helium-3 at ultralow temperatures. The practical application of the superfluidity of liquid helium-3 and many of its many other properties is now impossible to predict, just as it is impossible to do this for any fundamental discovery at its initial stage. But the experience of such discoveries shows that sooner or later they will definitely find their practical application.

This happened with the superfluidity of helium-4 discovered by Pyotr Kapitsa in 1937. Only in 2008 (that is, after more than 70 years) was the Large Hadron Collider built – the most powerful accelerator in the world, into which helium-4 was brought in a superfluid state at a temperature of 1.8 Kelvin. As one physicist explained to me, it is needed in the LHC to cool the magnets that hold the accelerated particles. Ordinary helium is not enough for this – it only cools the surfaces of the magnets, as a result of which the superconducting winding heats up quickly, which can lead to an explosion. And superfluid helium-4 has the ability to penetrate into the smallest cracks in the material (moreover, the smaller they are, the easier it penetrates there). It is this substance that allows you to cool the winding throughout its volume.

The truth is to explain why superfluid helium-4 penetrates better into the thinnest gap, and not into the one that is wider, – my friend scientist still refused: “It’s impossible to do it on the fingers!”. It is even more difficult to understand where the superfluid helium-3 discovered by Pitaevsky can be useful to us. Perhaps only our descendants will have to do this.

The question of the practical benefits of such research is often the reason for the insufficient funding of fundamental science in our country. What can not be said about the leading scientific countries of the world. There is usually no question of what kind of way out into practice fundamental research can give, – most often they simply generously invest in fundamental science. Why do they do it? It’s simple: we have long understood that such an approach almost always pays off handsomely. This can be seen from the rapidly developing technologies abroad.

“Do you want us to tell you what will come of our research? We don’t know it ourselves!” the theorists say. Lev Pitaevsky dealt with problems, in particular, in quantum mechanics, which, like the general theory of relativity, has no visual representations. These phenomena can only be described by equations. Pitaevsky’s teacher Landau once said: “We can even calculate what is impossible to imagine.” But many still demand from scientists to explain quantum phenomena on their fingers …

Lev Petrovich, as a truly talented person, showed remarkable abilities in other sciences as well. In particular, he was a non-trivial mathematician, which is clearly seen in a number of his works of a mathematical nature.

I got through to Pitaevsky’s friend Semyon Solomonovich Gershtein, and he remembered the time when they were both graduate students at Landau’s Institute for Physical Problems and lived in the same dorm room. “Once we had a very funny story with one integral,” says Gershtein. – First, I’ll say that Leva and I had different paces of life: I went to bed early, he stayed up late with calculations.

So, during the day I could not “take” the integral necessary for one of my work. I looked into Gradshtein-Ryzhik’s handbook, which we had in the room – but there was nothing like that in it. After a little thought, I nevertheless decided it myself and entered it in the margins with a pen. And at night, when Pitaevsky started his work, he was surprised to find this integral written by me in the reference book and was happy, because it was exactly what he needed, and for a completely different problem! “I puzzled over him all day, and at night I open the reference book, and he appeared!” Leva shared with me. But in general, he was distinguished by the fact that he grasped the essence of the subject with lightning speed. Sometimes I was even a little envious of his ability.”

Another amazing quality of Lev Petrovich, according to people who knew him, was the ability to switch from one scientific subject to another. For example, from ultra-low temperatures to ultra-high ones, working on plasma physics issues. In particular, he owns the work on the interaction of artificial Earth satellites with rarefied ionospheric plasma.

Why did Pitaevsky leave Russia? Yes, because the “magic” perestroika deprived him of the opportunity to work normally in his homeland. And yet, friends consider him primarily a Soviet and Russian scientist: “Italians may call him an “Italian” scientist, but this is not so. In essence, he was a Soviet, Russian scientist to the core. After all, all his discoveries were made in the USSR and Russia. Here he brought up as a teacher a large number of students, many of whom are now well-known world scientists.

Lev Pitaevsky always kept in touch with his native Institute of Physical Problems and with the Academy of Sciences. Until the last day of his life, he was a member of the editorial board of the leading Russian journal Uspekhi fizicheskikh nauk, where his numerous works were published.

Among other things, Lev Petrovich Pitaevsky was a wonderful person and an interesting conversationalist. Here is how Nikolai Tkachenko, an employee of the Institute for High Energy Physics, said about him: “As a truly outstanding person, he was devoid of any snobbery or arrogance. He was available to everyone. You could turn to him with absolutely any question – he always patiently explained.

His lectures were a model of pedagogical skill. He knew not only the shortest way, but certainly a beautiful way to deduce any complex result of science. For students who loved and respected him, he devoted as much time as they needed to understand the material. Now it is very, very difficult to find such teachers.”