Table of contents

A review is given of the dynamic structure of scalar resonances that exhibit a series of features that are unusual for two-quark systems. Recent experimental data on these resonances are analyzed by a very general method that is the most suitable for verifying different assumptions about the dynamic structure of the resonances. It is shown that the four-quark model is the most suitable for describing the known properties of scalar mesons. Attempts to identify any of the known scalar mesons with gluonium are unsuccessful. The phase ambiguity of elastic s-wave ππ-scattering and the mixing of the S* and δ⁰ resonances, which are model-independent for scalar resonances, are examined. A number of new experiments that may yield valuable information on the structure of scalar mesons is suggested. In particular, analysis of ππ →K and ππ → ππ data predicts the appearance of well-defined effects due to the S* (980) and ε(1400) resonances in the π⁺π⁻ηη reaction.

This article reviews the current status of studies by means of lasers of superdense nonideal plasmas. The main attention is paid to laser methods of generating plane steady-state shock waves with extremely high pressures. The role is discussed of various factors that complicate the design of laser experiments: generation of high-energy non-Maxwell electrons, plasma and hydrodynamic instabilities, restrictions on heat flux, etc. The advantages are pointed out of using high-frequency lasers and layered targets to obtain a plasma with extremal parameters.

The properties of narrow superconducting channels carrying a direct current are reviewed. Among the topics covered are the stability of the normal state of the current-carrying channel and the mechanism for a transition from this normal state to the superconducting state. In a homogeneous channel, the transition occurs through the formation of a critical nucleus and is a first-order phase transition. In a channel with inhomogeneities, the transition is quite different. In this case the normal state can exist only down to a certain value of the current, below which the normal state is absolutely unstable. The review is devoted primarily to the theory of the resistive state of narrow channels, which exists at currents above the critical Ginzburg-Landau current. The description is based on the concept of phase-slippage centers. Phenomenological models are discussed, as is a model of a fluctuational excitation of phase-slippage centers. The results obtained from the microscopic dynamic theory of superconductivity are discussed at length. Among these results are the voltage-current characteristic of the resistive state, the abrupt change in the voltage on this characteristic, and the structure of the phase-slippage centers.

The Third International Conference on the Study of Matter by the Method of Muon Spin Rotation and Related Problems was held on 18–20 April 1983 in Shimoda, Japan.