Table of contents

The recent progress concerning the Witten index in N=1 supersymmetric Yang–Mills theory is reviewed. Since 1982 there has been a controversy in counting vacua. The original calculation of the Witten index conflicted with expectations based on the chiral symmetry breaking picture. The controversy was resolved by Witten in 1998 who discovered additional disconnected components in the space of classical vacua in Yang–Mills theory compactified on a three-dimensional torus. We review the resolution of the controversy, describe those additional vacua and the corresponding gauge fields. We also discuss how the Witten index feels the physics of confinement and chiral symmetry breaking.

Ultrafast-optics applications of nonlinear-optical processes in gas-filled hollow fibers are briefly reviewed. The main physical processes behind the use of hollow fibers for efficient generation of unprecedentedly short light pulses, enhanced short-wavelength generation, and improvement of the sensitivity of nonlinear-optical gas-phase analysis are considered. These processes include self- and cross-phase modulation, coherent four-wave mixing, high-order harmonic generation, and stimulated Raman scattering. The methods to generate extremely short pulses, including few-cycle field waveforms, and to control such pulses are discussed.

Variations in meteorological parameters are largely due to periodic processes and can be forecast for several years. Many such processes are related to astronomical factors such as the gravitational influences of the Moon and the Sun, and the modulation of solar irradiance by lunar and planetary motion. The Moon, Jupiter, and Venus have the strongest effect. These influences produce lines in the spectra of meteorological variations, which are combinations of the harmonics of the frequencies of revolution of the planets, the Earth, and the Moon around the Sun with the harmonics of the lunar revolution around the Earth. Due to frequency differences between the orbital and radial motions, fine spectral features of three types appear: line splitting, line-profile complications due to radial oscillations, and additional lines due to the combination of radial-oscillation frequencies with perturbation harmonics.

The paper reviews the current progress in describing quantum intramolecular dynamics using merely symmetry principles as a basis. This closed qualitative approach is of particular interest because it is the only method currently available for a broad class of topical problems in the internal dynamics of molecules. Moreover, a molecule makes a physical system whose collective internal motions are geometrically structured, so that its description by perturbation methods requires a symmetry analysis of this structure. The nature of the geometrical symmetry groups crucial for the closed formulation of the qualitative approach is discussed. In particular, the point group of a molecule is of this type.