Table of contents

A study is made of the trajectories of free motion of test particles and photons in the Kerr metric, which describes the gravitational field of a rotating massive body. The trajectories are classified on the basis of the integrals of the motion, which have a clear physical meaning. The cases of a strong gravitational field in the neighborhood of a rotating black hole as well as the weak-field approximation describing the motion of particles in the gravitational field of a rotating star or galaxy are considered. The review includes bound states (orbits) in the field of a rotating mass, scattering and gravitational capture of particles and photons by a rotating black hole, trajectories of falling into a black hole, and the bending of light rays and the gravitational time delay of signals in the gravitational field of a rotating body.

The concept of the quantum gas is introduced and illustrated by numerous examples. The fundamentals of the theory of collective phenomena in quantum Maxwellian gases are surveyed in a simple and readily assimilated form, and possible experimental studies are outlined. Particular attention is devoted to weakly-damped spin waves. The spectrum of these waves is calculated and the magnetic susceptibility generalized. The results obtained are compared with experimental data on spin waves in gaseous H,³He,and ³He–⁴He quantum solutions. It is shown that, at low temperatures, spin-polarized Boltzmann gases exhibit longrange spin correlations which fall off as r^-1 at large distances. The equations of spin dynamics are solved for arbitrary temperatures and degrees of polarization, both in the weakly damped and diffusion regimes. The thermodynamics of spin-polarized gases and some of the features of transport phenomena are examined. Paramagnetic resonance and other collective effects in binary quantum gases are discussed. Magnetic and structural thermodynamic phase transitions in binary Maxwellian gases are predicted. Collective phenomena in semimagnetic semiconductors and analogous effects in the spectroscopy of Rydberg atoms and levitating electrons are discussed.

The status of optogalvanic (OG) spectroscopy, involving a change in the impedance of a gas or plasma, with tunable lasers is examined. The main advantage of this approach over the usual absorption spectroscopy is its high sensitivity. The OG effect in plasmas, glow discharges, hf discharges, hollow cathodes, obstructed discharges, neutral gases, etc., is studied. Optogalvanic studies of the spectra of both the ground and excited states of atoms and vibrational-rotational and electronic transitions in molecules, nonlinear spectroscopic phenomena, and interference of degenerate states and the use of the optogalvanic effect for stabilization of laser frequencies are described. A great deal of attention is given to the physical mechanisms involved in the formation of the OG signal. The possibilities for employing the optogalvanic effect in quantitative spectroscopy are evaluated.