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Lev Davidovich Landau

( Soviet physicist, Nobel Prize in Physics, 1962)

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Biography Lev Davidovich Landau
January 22, 1908, Mr.. - April 1, 1968
Soviet physicist Lev Davidovich Landau was born in the family of David and Lyubov Landau in Baku. His father was a prominent petroleum engineer who worked at the local oil industry, and his mother - a doctor. It dealt with physiological studies. The elder sister L. became a chemical engineer. While studying A. in high school and finished it brilliantly when he was thirteen years old, the parents felt that he was too young for university, and sent him to a year in Baku and Economic College. In 1922, Mr.. L. entered Baku University, where he studied physics and chemistry, two years later he transferred to the Physics Department of Leningrad University. By the time he was 19 years old, L. managed to publish four papers /. In one of them first used the density matrix - now widely used mathematical expression to describe the quantum energy states. After graduation in 1927. L. enrolled in the Leningrad Physical-Technical Institute, where he worked on the theory of magnetic electron and quantum electrodynamics.
From 1929 to 1931. L. was a scientific mission in Germany, Switzerland, Britain, the Netherlands and Denmark. There he met with the founders of a new time quantum mechanics, including Werner Heisenberg, Wolfgang Pauli and Niels Bohr. For life L. maintained friendly feelings towards Niels Bohr, have had a particularly strong influence. While abroad, L. conducted important studies of the magnetic properties of free electrons and, together with Ronald F. Peierls - relativistic quantum mechanics. These works are nominated him one of the leading theoretical physicists. He learned how to treat complex theoretical systems, and a handy skill to him later, when he began studies on low temperature physics.
In 1931, Mr.. L. returned to Leningrad, but soon moved to Kharkiv, the then capital of Ukraine. Tam L. becomes the head of the theoretical division Ukrainian Physico-Technical Institute. At the same time he holds the chair of theoretical physics at the Kharkov Engineering and Mechanics Institute in Kharkov University. Academy of Sciences awarded him in 1934. degree of Doctor of Physical and Mathematical Sciences without defending a thesis, and the following year he received the title of professor. In Kharkov L. published work on such diverse topics, . as the origin of stellar energy, . dispersion of sound, . energy transfer in collisions, . scattering, . magnetic properties of materials, . superconductivity, . phase transitions of substances from one form to another and the movement of flows of electrically charged particles,
. This makes him a reputation for exceptionally versatile theorist. Portfolio L. of electrically interacting particles proved to be useful later, when there is plasma physics - hot, electrically charged gases. Borrowing concepts from thermodynamics, he made a lot of innovative ideas for low-temperature systems. Portfolio L. share one characteristic - a virtuoso application of mathematical tools for solving complex problems. L. made a great contribution to the quantum theory and the study of nature and interactions of elementary particles.
. The unusually wide range of his research, . covering almost all areas of theoretical physics, . attracted to Kharkov of the talented students and young scientists, . including Evgeny Mikhailovich Lifshitz, . has become not only a close associate L., . but also his personal friend,
. Having grown up around L. Kharkov School turned into a leading center of Soviet theoretical physics. Convinced of the need for thorough preparation in all areas of theoretical physics, A. developed a rigid training program, which he called the 'theoretical minimum'. Requirements for applicants for the right to participate in a seminar led by him were so high that for thirty years, despite the never-ending stream comers, examinations 'teorminimumu' deposited only forty people. Those who overcame the exams, L. generously gave their time, gave them the freedom to choose the subject of investigation. With his students and family members, who lovingly called him Dau, he maintained friendly relations. To help his students A. in 1935. created a comprehensive course of theoretical physics, published them, and EM. Lifshitz in a series of textbooks, the contents of which the authors reviewed and updated during the next twenty years. These books have been translated into many languages around the world rightly considered classics. For creation of this course the authors in 1962. were awarded the Lenin Prize.
In 1937, Mr.. L. at the invitation of Peter Kapitza led the department of Theoretical Physics in the newly established Institute for Physical Problems in Moscow. But next year L. was arrested on false charges of spying for Germany. Only the intervention of Kapitsa, apply directly to the Kremlin, led to the liberation of Leningrad
When L. moved from Kharkiv to Moscow, the Kapitza experiments with liquid helium were in full swing. Gaseous helium to liquid state when cooled to temperatures below 4.2 K (in Kelvin absolute temperature measured from absolute zero, or temperature - 273,18 б° C). In this state of helium called helium-1. When cooled to a temperature below 2.17 K helium becomes a liquid, called helium-2, and possessing unusual properties. Helium-2 flows through tiny holes with such ease, as if he is absent viscosity. He rises through the vessel wall, as though it is not the force of gravity, and has a thermal conductivity, hundreds of times greater than the thermal conductivity of copper. Kapitsa called superfluid helium-2 liquid. But when checking the standard methods, such as measuring the resistance to torsional oscillations of the disk with a given frequency, it was found that helium-2 has no zero viscosity. Scientists have suggested that, . that the unusual behavior of helium-2 due to the effects, . related to the field of quantum theory, . instead of classical physics, . manifested only at low temperatures and are usually observed in solids, . since most of the substances under these conditions, freeze,
. Helium is an exception - if it is not subjected to very high pressure, remains liquid down to absolute zero. In 1938. Laszlo Tisza suggested that liquid helium is actually a mixture of two forms: a helium-1 (normal liquid) and helium-2 (superfluid). When the temperature drops almost to absolute zero, helium becomes a dominant component-2. This hypothesis may explain why, under different conditions observed different viscosity.
L. explained superfluidity, using a fundamentally new mathematical tools. While other researchers have used quantum mechanics to the behavior of individual atoms, it is considered the quantum states of the liquid is almost as if she were a solid. L. hypothesized the existence of two components of motion, . or excitement: phonons, . describing relatively normal rectilinear propagation of sound waves at small values of momentum and energy, . and rotons, . describing the rotational motion, . ie,
. more complex manifestation of excitations at higher values of momentum and energy. The observed phenomena are due to the contributions of phonons and rotons, and their interaction. Liquid helium, maintained LA, can be regarded as 'normal' component, immersed in superfluid 'background'. In the experiment on the expiration of liquid helium through a narrow slit of the superfluid component flows, while the phonons and rotons are faced with the walls that keep them. In the experiment with the torsional oscillations drive the superfluid component is negligibly weak effect, whereas the phonons and rotons are faced with the disk and slow down its movement. The ratio of the concentrations of normal and superfluid components depends on temperature. Rotons dominate at temperatures above 1K, phonons - below 0.6 K.
A Theory. and its subsequent improvements have allowed not only to explain the observed phenomena, but also to predict other unusual phenomena, such as the dissemination of two different waves, called the first and second sound, and have different properties. The first sound - these are ordinary sound waves, the second - the temperature wave. A Theory. helped to significantly advance the understanding of the nature of superconductivity ..
During the Second World War L. investigated the combustion and explosions, especially the shock waves at large distances from the source. After the war, and until 1962. He worked on the solution of various tasks, including studying the rare isotope of helium with an atomic mass of 3 (instead of the usual mass 4), and predicted for him the existence of a new type of wave propagation, which has been called his 'zero sound'. Note that the velocity of second sound in a mixture of two isotopes at a temperature of absolute zero to zero. L. participated in the creation of the atomic bomb in the Soviet Union.
Shortly before he was fifty-four years, L. got in a car accident and was badly damaged. Doctors from Canada, France, Czechoslovakia and the Soviet Union fought for his life. Within six weeks he remained unconscious for nearly three months did not recognize even their closest. A health condition. could not go to Stockholm to receive Nobel Prize in 1962, where he was awarded 'for the fundamental theory of condensed matter, especially liquid helium ". The award was presented to him in Moscow, Ambassador of Sweden to the Soviet Union. L. lived for six years but was never able to return to work. He died in Moscow from complications arising from injuries received by him.
In 1937, Mr.. L. married Concordia Drobantsevoy, engineer, food industry from Kharkov. They had a son, who worked later experimental physicists in the same Institute for Physical Problems, which has done so much his father. L. not tolerate pomposity, and his sharp, often witty critique sometimes gave the impression of him as a cold and even unpleasant. But P. Kapitsa, who knew L., spoke of him as 'a very kind and sympathetic, always ready to help unfairly hurt people'. After the death of L. EM. Lifshitz once remarked that A. 'always tried to simplify complex issues and show how you can more clearly the fundamental simplicity of the basic phenomena described by the laws of nature. He was particularly proud when he succeeded, as he said, 'trivializovat' challenge '
In addition to the Nobel and Lenin prizes L. been awarded three State Prizes of the USSR. He was awarded the title Hero of Socialist Labor. In 1946, Mr.. He was elected to the Academy of Sciences. His was elected a member of the Academy of Sciences of Denmark, the Netherlands and the United States, the American Academy of Arts and Sciences. French Physical Society, Physical Society of London and the Royal Society of London

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