The questions of the gaseous state physics of metals in the vicinity of the critical point are considered. A theory or mixed valence-electron states in the percolation clusters of overlapping atoms is represented being used for an interpretation of the experiment. A plasma nature of condensation near the critical point of gaseous metals is stated. Electric and electrodynamic properties of matter near a spread metal-nonmetal transition are analysed. so are plasma oscillations and optical spectra. A partial ionization at reduced densities and a multifold ionization at very high temperatures are briefly discussed.
The anomalous properties of zero-gap semiconductors doped with transition elements (iron, chromium) forming deep resonant donor states, i.e. states degenerated with the conduction band continuum, are described. The analysis of numerous investigations showing the peculiarities of the discussed materials being due to the correlated distribution of charged donors in a crystal as the result of inter-donor Coulomb interaction is presented. Among them the most striking anomaly is the enhancement of the electron mobility with a doping impurity concentration. The study of resonant states in semiconductors being a new trend of solid state physics is simultaneously of a practical interest, for it makes possible, for instance, to obtain materials with the highest electron mobilities. 2 tables. 23 figs. 32 refs.
The gauge theory of a high temperature superconductivity superconductivity in strongly correlated two-dimensional spin systems is reviewed. The basic data on statistics of elementary excitations in 2 + 1 D systems are given. The energy spectrum structure and the wave function are treated both in the long-wave and lattice limits. The phase states are classified using the methods of the topological quantum field theory. The thermodynamic and electrodynamic properties of anyon systems and experimental consequences of the Chern-Simons high-temperature superconductivity theory are discussed.
The review is devoted to the investigations of a mixed state of artificial microstructures based on type II superconductors. Three types of these microstructures are analysed: vortex microbridges, planar superlattices and multilayered systems. There is an analysis of the current situation and future trends in this field. 2 tabls. 33 figs. 124 refs.
This review article is devoted to results of theoretical and experimental investigations of properties of nanometer metal particles. First, the modern theory of equilibrium structures and shapes of small particles is presented. The next Section deals with the thermodynamics of small particles. It reflects the present state of the theory of surface forces for small particles, including crystalline ones. Validity conditions are pointed out for the standard approach, and an alternative approach is described which is adequate for particles surrounded by their saturated vapor. In it the Laplace pressure is not a real physical force, but a formal quantity that describes the size dependence of the chemical potential. Specific features are described of melting and interphase fluctuations in small particles. In describing the electron properties of the particles emphasis is laid on the smoothed level density and the size dependence of the Fermi energy. Some effects caused by this dependence are presented, in particular the mutual charging of particles of different sizes which manifests itself in an anomalously strong attraction between particles and so on. Magnetic properties of small particles are also described including macroscopic quantum tunneling of magnetization.
The paper reviews experimental results on the Shubnikov-de Haas effect in low-dimensional organic metals and superconductors.
The informal aspects, arising in the interpretation of physical experiments, of the theory of probability and mathematical statistics are discussed. The conditions that verifying experiments must satisfy are presented and the role of heuristic (extralogical) assertions is analyzed using the example of mathematical expectation. The principal hypotheses implicit in experiments are enumerated: the principle of reproducibility (the past will be repeated in the future); the principle of reasonable sufficiency; and, the statistical principle (better to predict something rather than nothing). Considerable attention is devoted to Fisher and multisample confidence intervals. It is noted that Fisher confidence intervals are inconsistent. The arguments for introducing contrivances into practical calculations of probabilities are enumerated: incompleteness of any system of hypotheses; subjective estimates of probabilities; adjoining of statistical ensembles; nonstationariness and instability; rare phenomena; and, the use of classical probabilities and the law of large numbers. It is concluded that the relative frequency of appearance (empirical probability) is a normal physical quantity in the sense that it admits physical measurement. Its abnormality is manifested in the fact that it is burdened, more than other physical quantities, with conventions and hypotheses which must be specially checked (verified).
