Table of contents

Different ways to calculate the spectral properties of fluctuating electromagnetic fields produced by solids are reviewed, all of which essentially reduce to solving the Maxwell equations for a specified geometry and boundary conditions and then using the fluctuation--dissipation theorem. It is shown that in the practical case of plane-layered solids, all correlation characteristics of thermal fields can be expressed in terms of the Fresnel coefficients. The experimental results on thermally stimulated electromagnetic fields from solids are in qualitative and quantitative agreement with model calculations and theoretical expectations. The dispersion interaction between solid bodies in different thermodynamic states, the fluctuating fields as a means of body-to-body energy transfer, and the shift, broadening, and deexcitation of energy levels in a particle near a solid surface are discussed using the theory of thermally stimulated electromagnetic fields.

High-power free electron lasers (FELs), recently developed sources for producing intense femtosecond pulses of vacuum ultraviolet (VUV) radiation, offer new ways of studying the interaction of radiation with matter. In this paper, a first series of experiments on the laser excitation of atomic cluster beams is reviewed, which showed that intense VUV pulses interact with clusters very differently than their optical or near infrared (IR) counterparts do. The first experimental results on cluster beam spectroscopy performed with intense VUV-FEL pulses are examined. FEL operation principles and performance parameters are briefly discussed. How intense ultrashort IR and VUV pulses excite clusters is analyzed, the interaction parameters between radiation and clusters are covered, and the formation and heating mechanisms of cluster plasma are explored. What is similar and fundamentally different between the ways IR and VUV radiations excite clusters is pointed out. Some other applications of VUV and soft X-ray FEL radiation are reviewed as well.

The method of mirror images is used to calculate transition radiation (TR) at the plane interface between a vacuum and an ideally conducting medium. The total field is considered (that is, the TR field plus the fields of the uniformly moving charge and its mirror image) and its evolution in space and time is traced, considering fields as functions of space coordinates and time rather than represented by spectral components. Conditions are analyzed under which the separation and measurement of a TR field are possible.

Recent years have added very much to our knowledge of the structure of the Universe and elementary interactions which, combined with the critical rethinking of long-known results and ideas, gives considerable topical relevance to the questions listed in this paper. Compiling this list, the author had no notion of any targeting and the typical 'WHAT FOR' and 'WHY' questions were considered as mere abbreviations for "Does a (possibly yet unknown) law of Nature exist with which the property or phenomenon under study can be explained?" The list of problems reflects the scientific interests of the author and so does not claim to be comprehensive.

A scientific session of the Physical Sciences Division of the Russian Academy of Sciences (RAS) was held in the Conference Hall of the P N Lebedev Physical Institute, RAS on November 26, 2008. The session was dedicated to the 100th anniversary of the birth of Sergei Mikhailovich Rytov. The following reports were presented at the session:

(1) Gulyaev Yu V (V A Kotel'nikov Institute of Radioengineering and Electronics, RAS, Moscow) "Sergei Mikhailovich Rytov (Opening address)"; (2) Barabanenkov Yu N (V A Kotel'nikov Institute of Radioengineering and Electronics, RAS, Moscow) "Asymptotic limit of the radiative transfer theory in problems of multiple wave scattering in randomly inhomogeneous media"; (3) Kaplan A E, Volkov S N (Johns Hopkins University, Baltimore, USA) "Local fields in nanolattices of strongly interacting atoms: nanostrata, giant resonances, 'magic numbers', and optical bistability"; (4) Klyatskin V I (A M Obukhov Institute of Atmospheric Physics, RAS, Moscow) "Modern methods for the statistical description of dynamical stochastic systems"; (5) Dolin L S (Institute of Applied Physics, RAS, Nizhny Novgorod) "Development of the radiative transfer theory as applied to instrumental imaging in turbid media".

An abridge version of the reports is given below. • Sergei Mikhailovich Rytov (Opening address), Yu V Gulyaev Physics-Uspekhi, 2009, Volume 52, Number 5, • Asymptotic limit of the radiative transfer theory in problems of multiple wave scattering in randomly inhomogeneous media, Yu N Barabanenkov Physics-Uspekhi, 2009, Volume 52, Number 5, • Local fields in the nanolattices of strongly interacting atoms: nanostrata, giant resonances, 'magic numbers', and optical bistability, A E Kaplan, S N Volkov Physics-Uspekhi, 2009, Volume 52, Number 5, • Modern methods for the statistical description of dynamical stochastic systems, V I Klyatskin Physics-Uspekhi, 2009, Volume 52, Number 5, • Development of the radiative transfer theory as applied to instrumental imaging in turbid media, L S Dolin Physics-Uspekhi, 2009, Volume 52, Number 5,