International Journal of Modern Physics A

An account of the inclusive production of K mesons in electron-positron annihilation is given. The most recent measurements on the cross section are exhibited and compared with the predictions of the Lund model. The model gives a satisfactory agreement with the experimental data. The results from different experiments on cross section, the mean multiplicity per multihadronic event and various other characteristics are found to be consistent.

Two-body B→PP decays are studied by using SU(4) transformation properties of the effective weak nonleptonic Hamiltonian. Decay amplitudes and branching relations are obtained in the SU(4) framework.

We investigate the contributions of matter fields to the Hartle-Hawking wave function of the Universe in the one-loop approximation. The values ζ(0), which describe the scaling behavior of the wave function calculated on the background representing the part of four-dimensional DeSitter sphere, are calculated for scalar, electromagnetic, graviton, spin-1/2 and spin-3/2 fields. The ζ-function technique is used and developed for these calculations. The obtained results can be applied to a detailed investigation of the structure of the Hartle-Hawking wave function.

The properties of the bound system charge-dyon (so-called “dyonium”) in the external electromagnetic field are considered. It is shown that the spectrum of dipole radiation of the dyonium contains direct information on spatial parity violation in electrodynamics with magnetic charge. It is found that the P noninvariance of this system leads to essential differences between the Stark and Zeeman effects for a hydrogen atom and those for dyogen. The photoionization process of the hydrogen-like atom in the field of the magnetic charge is calculated. It is shown that the corresponding angular distribution of the photoelectron has an essential asymmetry due to the P parity breaking.

Scale-invariant (flat) fluctuation spectra are the most generic outcomes of inflation. However, current observations of large scale structure require more fluctuation power on large scales than flat spectra give. One such observation concerns the existence of large cosmological bubbles on the scales ~ (20–50) Mpc in the galaxy distribution. We attempt an explanation of these structures based on an inflationary model containing two scalar fields. One of these fields undergoes a first order phase transition, owing to the evolution of the other. We study the distribution of bubbles formed during the phase trnasition and show that for a wide range of choice of the free parameters in our model, a few bubbles can survive and grow to become the bubble structures observed at present.

We study quantum Maxwell and Yang-Mills theory on orientable two-dimensional surfaces with an arbitrary number of handles and boundaries. Using path integral methods we derive general and explicit expressions for the partition function and expectation values of contractible and noncontractible Wilson loops on closed surfaces of any genus, as well as for the kernels on manifolds with handles and boundaries. In the Abelian case we also compute correlation functions of intersecting and self-intersecting loops on closed surfaces, and discuss the role of large gauge transformations and topologically nontrivial bundles.

We consider para-Bose and para-Fermi oscillators within the framework of thermofield dynamics. For these systems, we construct the transformation relating the thermal vacuum state to the zero temperature vacuum. This construction makes use of a nonlinear realization of the single mode para-Bose (para-Fermi) algebra in terms of a single boson.

We discuss constraints on electric charge nonconservation and minicharged particles implied by terrestrial, astrophysical and cosmological considerations. We also suggest possible methods for detection of these particles in underground detectors.

A search has been performed for weakly interacting neutral light scalar and pseudoscalar particles in a proton-iron beam dump experiment via the Bethe-Heitler process. No positive signal was observed. Limits are derived on the masses of these particles in the framework of the Standard Model and its minimal supersymmetric extension (MSSM) comparing the experimental results with expectations for Bethe-Heitler e⁺e⁻ and μ⁺μ⁻ pair production. The Higgs particle of the SU_2L×U₁ Standard Theory is excluded for masses in the range m_H<0.9 MeV at 95% CL. Limits on light Higgs particles of the MSSM and Peccei-Quinn like axions are derived.

A semiclassical understanding of the anomalies of the axial singlet and nonsinglet currents in massless QCD (coupled to an external adiabatically turned on electromagnetic field) is developed. In particular, it is clarified how these anomalies manifest themselves in the context of spontaneous symmetry breaking. For the nonsinglet current the anomaly manifests itself as a final coherent state of massless pions; for the singlet current it is argued that there is a cancellation between the gluonic and electromagnetic contributions to the anomaly, which is verified explicitly using the 1/N expansion.

We consider the low-energy predictions for sin²θ_W and τ_proton of SUSY GUT’s along the lines of Ref. 1. Special attention is paid to the dependence on the mass spectrum of superpartners and possible heavy inhabitants of the Great desert. The minimal and finite SUSY SU(5) models with light and heavy t squark and additional higgsino are considered. It is shown that modern precise LEP data are naturally reproduced within the finite SUSY SU(5) GUT with both light and heavy t squark and light higgsino with a reasonable SU(5) splitting.

Using the finite-size effects, the scaling dimensions and correlation functions of the main operators in continuous and lattice models of 1d spinless Bose-gas with pairwise interaction of rather general form are obtained. The long-wave properties of these systems can be described by the Gaussian model with central charge c=1. The disorder operators of the extended Gaussian model are found to correspond to some nonlocal operators in the XXZ Heisenberg antiferromagnet. This same approach is applicable to fermionic systems. Scaling dimensions of operators and correlation functions in the systems of interacting Fermi-particles are obtained. We present a universal treatment for 1d systems of different kinds which is independent of the exact integrability and which gives universal expressions for critical exponents through the thermodynamic characteristics of the system.

An earlier suggestion that the chiral phase transition in QCD for two flavors of massless quarks might be a second-order transition has gained credibility as a result of recent numerical simulations. One can test this hypothesis, and draw very specific quantitative consequences from it, using universality and renormalization group ideas. This hypothetical second order phase transition is in the universality class of a four component isotropic Heisenberg antiferromagnet—a model which has been investigated intensely by condensed matter physicists. Existing calculations can be adapted to yield predictions for critical exponents governing the QCD transition. The perturbation due to small equal quark masses maps onto an external staggered magnetic field; that due to unequal quark masses is effective only in second order and generates a quadratic anisotropy. Several other potential applications of the renormalization group to related questions are suggested, including a model of the tricritical point which arises with finite strange quark mass, and a model for the dynamic critical behavior.