Modern Physics Letters A

The magnetic properties of charged vector boson gas are studied in the very weak, and very strong (near critical value) external magnetic field limits. When the density of the vector boson gas is low, or when the external field is strong, no true Bose–Einstein condensation occurs, though significant amount of bosons will accumulate in the ground state. The gas is ferromagnetic in nature at low temperature. However, Bose–Einstein condensation of vector bosons (scalar bosons as well) is likely to occur in the presence of a uniform weak magnetic field when the gas density is sufficiently high. A transitional density depending on the magnetic field seems to exist below which the vector boson gas changes its property with respect to the Bose–Einstein condensation in a uniform magnetic field.

We discuss the essence of the zero-point in fixed-point gauge of nonperturbative QCD and describe how to set the zero-point appropriately in deriving the nonperturbative quark–gluon three-point vertex functions including gluon condensates.

Gauge-invariant systems of a general form with higher order time derivatives of gauge parameters are investigated within the framework of the BFV formalism. Higher order terms of the BRST charge and BRST-invariant Hamiltonian are obtained. It is shown that the identification rules for Lagrangian and Hamiltonian BRST ghost variables depend on the choice of the extension of constraints from the primary constraint surface.

The geometry of torsion defects in Weitzenböck space–time is investigated. Conformal de Sitter space–time outside the defect is obtained. Geodesic motion of test particles outside the torsion wall is given. Torsion defect wall is shown to have repulsive gravitational fields. Static torsion defect is obtained by gluing together two half Minkowski spaces across a torsion wall junction.

We investigate the possibility to look for new physics by the measurement of the four-jet cross-section at LHC and Tevatron. In particular, we consider the model with scalar colour octet and the supersymmetric model with R-parity violation. In both models, pair produced new particles decay into two jets thus leading to four-jet events. Therefore, the measurement of the four-jet events allows one to look for new physics. The main background comes from the standard QCD four-jet events. We find that it would be possible to discover scalar colour octet particles with a mass ≤ 900 GeV at the LHC and up to about 175 GeV at the Tevatron.

Within a Liouville approach to noncritical string theory, we argue for a nontrivial commutation relation between space and time observables, leading to a nonzero space–time uncertainty relation δx δt>0, which vanishes in the limit of weak string coupling.

A number of nontrivial vacua of the Yang–Mills gauge theory which are extended in space are derived. For the vacuum solution with a constant "magnetic" field of one color species, the elementary excitations of the other species are circularly polarized, with a spectrum much like the Landau levels of nonrelativistic electrons in a constant magnetic field.

Perturbation theory, which represents a Wilson loop in the SU(2) gluodynamics as an integral over all the orientations in color space, in the nonperturbative QCD vacuum and the non-Abelian Stokes theorem is applied to a derivation of the correction to the string effective action in the lowest order in the coupling constant g. This correction is due to the interaction of perturbative gluons with the string worldsheet and affects only the coupling constant of the rigidity term, while its contribution to the string tension of the Nambu–Goto term vanishes. The obtained correction to the rigidity coupling constant multiplicatively depends on the color "spin" of the representation of the Wilson loop under consideration and a certain path integral, which includes the background Wilson loop average.