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A Joint session of the P N Lebedev Physical Institute Research Council of the Academy of Sciences and the Scientific session of the Physical Sciences Division of the Russian Academy of Sciences and the United Physical Society of the Russian Federation was convened on 6 April 2009 to mark the 75th anniversary of the P N Lebedev Physical Institute of the Academy of Sciences (FIAN). The following papers were read to the session:

(1) Mesyats G A (P N Lebedev Physical Institute RAS) "75 years of the P N Lebedev Physical Institute RAS which traces back its origin to the Physics Room of Peter the Great's Kunstkamera created 225 years ago"; (2) Bolotovskii B M (Division of Theoretical Physics, P N Lebedev Physical Institute RAS) "Vavilov–Cherenkov radiation"; (3) Kopaev Yu V (Division of Solid State Physics, P N Lebedev Physical Institute RAS) "Toroidal states in crystals"; (4) Kardashev N S (Astro-Cosmic Center of the P N Lebedev Physical Institute RAS) "Science program of the Radioastron mission"; (5) Zatsepin G T (Nuclear Research Institute RAS), Roganova T M (M V Lomonosov Moscow State University, D V Skobeltsyn Nuclear Physics Research Institute) "Cosmic ray studies"; (6) Masalov A V (Optics Division, P N Lebedev Physical Institute RAS) "Spectroscopy: from atoms to cosmic objects"; (7) Gubin M A, Velichansky V L (Division of Quantum Radiophysics, P N Lebedev Physical Institute RAS) "Small-size optical frequency standards"; (8) Dagkesamanskii R D (Radioastronomical Observatory in Pushchino of the Astro-Cosmic Center of the P N Lebedev Physical Institute RAS) "Prospects for radioastronomical research in Pushchino".

Articles written on the basis of these talks are printed in this special issue of Uspekhi Fizicheskikh Nauk (Usp. Fiz. Nauk 179 (11) 1145 – 1256 (2009) [English version: Phys. Usp. 52 (11) (2009] journal. • P N Lebedev Physical Institute RAS: past, present, and future, G A Mesyats Physics-Uspekhi, 2009, Volume 52, Number 11, Pages 1084–1097 • Vavilov–Cherenkov radiation: its discovery and application, B M Bolotovskii Physics-Uspekhi, 2009, Volume 52, Number 11, Pages 1099–1110 • Toroidal ordering in crystals, Yu V Kopaev Physics-Uspekhi, 2009, Volume 52, Number 11, Pages 1111–1125 • Radioastron: a radio telescope many times the size of Earth. Research program, N S Kardashev Physics-Uspekhi, 2009, Volume 52, Number 11, Pages 1127–1137 • Cosmic ray investigations, G T Zatsepin, T M Roganova Physics-Uspekhi, 2009, Volume 52, Number 11, Pages 1139–1146 • Spectroscopy: from atoms to cosmic objects, A V Masalov Physics-Uspekhi, 2009, Volume 52, Number 11, Pages 1147–1152 • Laser frequency standards at the P N Lebedev Physical Institute, V L Velichansky, M A Gubin Physics-Uspekhi, 2009, Volume 52, Number 11, Pages 1153–1158 • The Pushchino Radio Astronomy Observatory of the P N Lebedev Physical Institute Astro Space Center: yesterday, today, and tomorrow, R D Dagkesamanskii Physics-Uspekhi, 2009, Volume 52, Number 11, Pages 1159–1167

This paper reviews the history of the P N Lebedev Physical Institute of the Russian Academy of Sciences (FIAN in Russ. abbr.). Major achievements of FIAN scientists are discussed, current activities are described, and future prospects are outlined.

The history of the discovery of the Vavilov–Cherenkov effect is outlined. Several important applications of the effect are discussed.

Phase transitions to ordered states, which correspond to the toroidal family of multipoles known in electrodynamics, are discussed. The ordering of toroidal moments may either occur simultaneously with their formation (as in superconductivity) or may follow it (at lower temperatures). In addition to electrodynamic toroidal moments corresponding to either poloidal charge currents or a spin configuration, a toroidal state corresponding to poloidal spin currents is possible.

A number of ground-based radio telescopes and one in a terrestrial orbit with the apogee at about the Earth–Moon distance have been combined to make an interferometer that provides the angular resolution up to a few microarcseconds for exploring astronomical objects such as pulsars, star formation regions, and black holes. Black hole horizon physics, cosmic ray acceleration regions, and the hypothetical wormhole entrances are becoming accessible to study for the first time.

The history of cosmic ray research at the Lebedev Institute beginning with the first work and continuing up to now is reviewed. The milestones and main avenues of research are outlined. Pioneering studies on the nuclear cascade process in extensive air showers, investigations of the Vavilov–Cherenkov radiation, and some work on the origin of cosmic rays are discussed. Recent data on ultrahigh-energy particle detection at the Pierre Auger Observatory and the High Resolution Fly's Eye (HiRes) experiments are presented.

A review is given of spectroscopic research pursued in the Division of Optics at the P N Lebedev Physical Institute (FIAN), which has yielded significant results in recent years. A case in point is primarily the development of instrumentation installed on board artificial Earth satellites and intended for the ultraviolet and X-ray spectroscopy of the solar corona. Furthermore, progress is reviewed in the area of precision atomic spectroscopy, where an arsenal of state-of-the-art techniques enables observing optical resonances ranging in width from several hertz to several hundred hertz.

A brief review is made of the investigations conducted at the Laboratory of Frequency Standards at the P N Lebedev Physical Institute (FIAN) Division of Quantum Radiophysics along an important line of inquiry into the development of quantum frequency standards—the elaboration of a subminiature clock based on the coherent population trapping effect in alkali metal atoms with semiconductor laser pumping (frequency stability of 10⁻¹¹–10⁻¹² for an averaging time of ∼ 10⁴ s) and compact master oscillators/optical clocks with a frequency stability of 10⁻¹⁴–10⁻¹⁵ (for an averaging time of 1 s) based on He–Ne/CH₄ and fiber femtosecond lasers.

The development of Russian (formerly Soviet) radio astronomy is indissolubly linked with the P N Lebedev Physical Institute (LPI), Russian Academy of Sciences. From the late 1940s, the institute conducted most of its radio astronomy research in the Crimea, at stations or on field trips; in the late 1950s, the center of gravity of research moved to the southern Moscow region, where one of the largest radio astronomy observatories in the country and in the world was developed within less than twenty years. The observatory unique instrumentation system is briefly reviewed in a historical perspective. Key research areas and some major achievements are outlined, and the prospects of the observatory as (currently) part of the LPI Astro Space Center are examined.

This article describes the history of the creation and further development of Landau's famous works on phase transitions, diamagnetism of electron gas (Landau levels), and quantum transitions at a level crossing (the Landau–Zener phenomenon), and its role in modern physics.

Newly discovered evidence and archival material are presented which give a new insight into the life and career of one of the greatest physicists of the twentieth century — Leonid Isaakovich Mandelstam.