Table of contents

Recent studies of meson spectra have enabled the resonance structure of the IJ^PC = 00⁺⁺, 10⁺⁺, 02⁺⁺, 12⁺⁺, and IJ^P = 1/2 0⁺ waves to be found for masses ranging up to 1900 MeV, thus fully reconstructing the 1³ P₀q and 2³P₀q meson multiplets. There is firm experimental evidence for the existence of five scalar–isoscalar states in this mass range, four of which are q states and members of the 1³ P₀q and 2³ P₀q nonets, whereas the fifth falls out of the quark picture and displays all the properties of the lightest possible scalar glueball. A dispersion analysis of the 00⁺⁺ wave elucidates how the mixture of the pure glueball state (or gluonium) with neighboring scalar q states forms: three scalar mesons, namely two relatively narrow f₀(1300) and f₀(1500) resonances and a very broad f₀(1530_-250⁺⁹⁰) resonance, share the gluonium, the broad resonance being the gluonium's descendant and accounting for about 40 to 50% of it.

The calculation of the density of states for the Schrödinger equation with a Gaussian random potential is equivalent to the problem of a second-order transition with a 'wrong' sign for the coefficient of the quartic term in the Ginzburg–Landau Hamiltonian. The special role of the dimension d = 4 for such a Hamiltonian can be seen from different viewpoints but is fundamentally determined by the renormalizability of the theory. The construction of an ε expansion in direct analogy with the phase-transition theory gives rise to the problem of a 'spurious' pole. To solve this problem, a proper treatment of the factorial divergency of the perturbation series is necessary. Simplifications arising in high dimensions can be used for the development of a (4–ε)-dimensional theory, but this requires successive consideration of four types of theories: a nonrenormalizable theories for d > 4, nonrenormalizable and renormalizable theories in the logarithmic situation (d = 4), and a super-renormalizable theories for d < 4. An approximation is found for each type of theory giving asymptotically exact results. In the (4–ε)-dimensional theory, the terms of leading order in 1/ε are only retained for N~1 (N is the order of the perturbation theory) while all degrees of 1/ε are essential for large N in view of the fast growth of their coefficients. The latter are calculated in the leading order in N from the Callan–Symanzik equation with the results of Lipatov method used as boundary conditions. The qualitative effect is the same in all four cases and consists in a shifting of the phase transition point in the complex plane. This results in the elimination of the 'spurious' pole and in regularity of the density of states for all energies. A discussion is given of the calculation of high orders of perturbation theory and a perspective of the ε expansion for the problem of conductivity near the Anderson transition.

Experimental and theoretical data on tunneling and barrier-suppression ionization of atoms and atomic ions in a low-frequency laser radiation field are considered. The yields of single- and multi-charged ions, the energy and angular distributions of photoelectrons, and effects of the laser pulse length and laser polarization are analyzed.

The scientific and social activities of S I Vavilov are discussed based on documents that have become available in the last decade.

A kinetic equation for probe particles colliding with buffer gas molecules is proposed, which is modified to include the concept of wave function collapse during particle collisions. Some consequences of such modification are discussed along with the possibilities for their observation.

It is shown that at low concentrations of charged particles conditions can be realized in a magnetized unstable-to-drift plasma for which concentration perturbations are comparable to the concentration itself. The electron temperature is then determined by potential fluctuations, and the drift oscillation wavelength is of the order of the Debye length.