Table of contents

QCD vacuum properties and the structure of color fields in hadrons are reviewed using the complete set of gauge-invariant gluon field correlators. QCD confinement is produced by correlators with a certain Lorentz structure, which violate the Abelian Bianchi identities and are therefore absent in QED. These correlators are used to define an effective colorless field satisfying the Maxwell equations with a nonzero effective magnetic current. In the language of correlators and the effective field, it is shown that non-Abelian interaction of gluon gauge fields leads to quark confinement due to effective circular magnetic currents that squeeze gluon fields into a string in accordance with the 'dual Meissner effect'. Distributions of effective gluon fields in mesons, baryons, and glueballs with static sources are plotted.

Results of a recent supercomputer analysis of lattice QCD with dynamical fermions are presented. Gluon fields inside mesons and baryons with static (infinitely heavy) quarks are described. The breaking, due to the creation of a quark–antiquark pair from a vacuum, of the string that couples quarks into hadrons is discussed. The finite temperature QCD phase transition is considered. The results obtained show that the QCD vacuum behaves as a dual superconductor and that color confinement is due to the formation of a dual analog of the Abrikosov string.

Lattice measurements provide a unique possibility to directly study the anatomy of vacuum fluctuations, that is, their action and entropy. In this review, we discuss properties of vacuum fluctuations that are naturally called magnetic monopoles, or scalar particles. Magnetic monopoles are defined on the lattice as closed trajectories. One of the basic observations is that the length of these trajectories is measured in physical units (fermi) and does not depend on the lattice spacing a. Their thickness, on the other hand, determined in terms of the distribution of the non-Abelian action, is of order of the resolution a. Moreover, these infinitely thin — within presently available resolution — trajectories are unified into infinitely thin surfaces.

Analysis of experimental data from the Crystal Barrel Collaboration on the in-flight pp̄ annihilation into mesons revealed a large group of mesons in the 1900 – 2400-MeV range, allowing the systematization of quark–antiquark states in the (n, M²)- and (J, M²)-planes (n being the radial quantum number, and J the spin of a meson of mass M). From the data, meson trajectories in these planes are approximately linear and have a universal slope. A detailed discussion of the scalar meson sector is given for which, based on a recent K-matrix analysis, the nonet classification of quark–antiquark states places two scalar nonets — the basic nonet and that of the first radial excitation — in the range below 2000 MeV. Two isospin 0 scalar states — the broad resonance f₀(1200–1600) and the light σ-meson — do not fit into the quark–antiquark classification, i.e., are exotic. The ratios between the coupling constants for hadronic decays to the ππ, K, ηη and ηη' states point to the gluonium nature of the broad state f₀(1200–1600).

Microstructure fibers have opened a new phase in nonlinear optics. Due to their unique properties, fibers of this type radically enhance all the basic nonlinear-optical phenomena, offering new strategies for frequency conversion, spectral transformation, and control of ultrashort laser pulses. These fibers allow supercontinuum radiation to be efficiently generated using nano- and subnanojoule femtosecond pulses. Here, we analyze the physical mechanisms behind the enhancement of nonlinear-optical interactions of ultrashort pulses in microstructure and hollow photonic-crystal fibers and discuss applications of microstructure fibers for highly efficient supercontinuum generation and frequency conversion of femtosecond laser pulses.

A common laboratory facility for creating glowing flying plasmoids akin to a natural ball lightning, allowing a number of experiments to be performed to investigate the main properties of ball lightning, is described.