[en] Detailed study of the structure in the rapidity plane allows to determine the amount of single and double diffraction within a cluster model. From semi-inclusive data on correlations the average number of particles due to decay of one cluster can be estimated

[en] We review the current understanding of the behaviour of inclusive cross sections at small x and large Q² in terms of Altarelli-Parisi evolution, the BFKL equation, and Regge theory, asking in particular to what extent they are mutually consistent. (author)

[en] An expectation value of the energy-momentum tensor for a massive scalar field propagating in a Robertson-Walker universe is calculated by taking account of both effects caused by the particle creation and the vacuum polarization. A special case of the Chitre-Hartle universe which enables us to perform an explicit calculation is also treated. (author)

[en] Dynamical features of tagged particles are studied in a one dimensional system for k  =  0 and 1, where the particles A have a bias to hop one step in the direction of their nearest neighboring particle. represents purely diffusive motion and represents purely deterministic motion of the particles. We show that for any , there is a time scale t ^* which demarcates the dynamics of the particles. Below t ^*, the dynamics are governed by the annihilation of the particles, and the particle motions are highly correlated, while for , the particles move as independent biased walkers. t ^* diverges as , where and . is a critical point of the dynamics. At , the probability , that a walker changes direction of its path at time t, decays as and the distribution of the time interval between consecutive changes in the direction of a typical walker decays with a power law as . (paper)

[en] Power dissipation by transit-time damping is investigated analytically and numerically using a perturbation expansion and a test-particle code, respectively. Excellent agreement between the two methods is found for both one-dimensional and multidimensional systems. It is shown that the local power dissipation can take on positive or negative values depending on position, implying that particles not only carry off energy from localized fields, but redistribute it within them. The results are applied to estimate the arrest scales of the collapsing wave packets found in strongly turbulent plasmas. Arrest scales in the ranges (14--23)λ_D and (16--26)λ_D are found for two- and three-dimensional wave collapse, respectively. These estimates are consistent with results from particle-in-cell simulations, which yielded arrest scales of ∼14λ_D in 2D and ∼20λ_D in 3D, and with experimental results that implied arrest at scales of (17--30)λ_D in 3D. The previously problematical outcome that 3-D collapse is arrested at a longer scale than in 2D, despite its stronger nature, results because the larger fraction of high-velocity particles in the 3-D plasma velocity distribution leads to stronger transit-time damping than in the corresponding 2-D system. It is argued that transit-time dissipation will arrest the collapse of particularly intense wave packets at even longer scales due to the increase in the local Debye length caused by localized heating near the center of these wave packets and due to the formation of high-velocity tails by transit-time acceleration

[en] In a recent paper (Infeld and Senatorski 2003 J. Phys.: Condens. Matter 15 5865) we confirmed Feynman's hypothesis on how circular vortices can be created from an oppositely polarized linear pair in a Bose-Einstein condensate. This was done by perturbing the original pair numerically, so that a circular vortex (or array of identical circular vortices) was created as a result of reconnection. These circular vortices were then checked against known theoretical relations binding velocities and radii. Agreement to a high degree of accuracy was found. Here in part II, we give examples of the creation of several different vortices from one linear pair. All are checked as above. We also confirm the limit of separation of the line vortices below which mutual attraction, followed by annihilation, prevents the Feynman metamorphosis. Other possible modes of behaviour are illustrated

[en] We use a potential model incorporating a carefully estimated value of the strong-interaction coupling strength to calculate the energy-level spacings in t-quarkonium. We find that, for a top-quark mass of about 40 GeV the energy difference of the first two levels in t quarkonium is about 700 MeV, or more than 100 MeV larger than the analogous energy differences in charmonium and b quarkonium

[en] An aggregation-migration-annihilation model is proposed for a two-species-group system. In the system, aggregation reactions occur between any two aggregates of the same species and migration reactions between two different species in the same group and joint annihilation reactions between two species from different groups. The kinetics of the system is then investigated in the framework of the mean-field theory. It is found that the scaling solutions of the aggregate size distributions depend crucially on the ratios of the equivalent aggregation rates of species groups to the annihilation rates. Each species always scales according to a conventional or modified scaling form; moreover, the governing scaling exponents are nonuniversal and dependent on the reaction details for most cases.

[en] The character of the functional dependence of the cross-sections for inclusive and exclusive reactions on the energy of colliding particles has been established on the basis of the principles of casuality, spectrality and unitarity

No abstract available