A characterization of adding machine maps

Let f :X→X be a continuous map of a compact metric space to itself. We prove that f is topologically conjugate to an adding machine map if and only if X is an infinite minimal set for f and each point of X is regularly recurrent. Moreover, if X is an infinite minimal set for f and one point of X is regularly recurrent, then f is semiconjugate to an adding machine map.     

On factorization, quark counting and vector dominance

Using an eikonal structure for the scattering amplitude, Block and Kaidalov [1] have derived factorization theorems for nucleon-nucleon, and scattering at high energies, using only some very general assumptions. We present here an analysis giving experimental confirmation for factorization of cross sections, nuclear slope parameters B and -values (ratio of real to imaginary portion of forward scattering amplitudes), showing that: – the three factorization theorems [1] hold, – the additive quark model holds to , – and vector dominance holds to better than . Received: 6 November 2001 / Revised version: 29 November 2001 / Published online: 8 February 2002     

Influence of disorder on microcavity polariton linewidths

Polariton linewidths have been measured in a series of microcavities with different excitonic and cavity inhomogeneous broadening in the weak-disorder regime. We show experimentally that the behaviour of the polariton linewidths as a function of the detuning depends on the asymmetric line shape of an inhomogeneously broadened exciton line and particularly the disorder effect can be modulated and cancelled around resonance. When the disorder contribution is minimal, the behaviour of the cavity polariton linewidths tends to one of the homogeneous broadening system.     

A new model for auroral breakup during substorms

A model for substorm breakup is developed, based on (1) the relaxation of stretched (closed) dipolar field lines, and (2) the formation of an incipient current wedge within a single arc structure. It is argued that the establishment of a coupled current structure within a single arc leads to a quasistable system, i.e. the prebreakup regime. Perturbation of the prebreakup structure leads to an instability criterion. It is found, consistent with observations, that the narrower auroral arcs at lower L shells undergo the most explosive poleward expansion. According to this model, the precise location at which breakup occurs depends on the O⁺ density in the plasma sheet, the level of magnetic activity (K_p), and the intensity of the substorm westward electrojet in the ionosphere. An enhancement of any of these features will cause breakup to occur at lower L shells. Comparison of the proposed model with the Heppner-Maynard polar-cap potential model indicates that breakup is restricted to the west of the Harang discontinuity, consistent with observations from the Viking satellite     

Electron spin resonance study of free radicals in the radiation grafting of butadiene to poly(vinyl chloride)

The kinetics of the disappearance of propagating butadiene radicals produced in the grafting of butadiene to poly(vinyl chloride) was followed by electron spin resonance measurements. The radical species observed in the temperature range 213–298°K is the conjugated allylic radical: The reaction conditions were adjusted to provide a highly viscous medium in which the propagation reaction took place. Under these conditions the radicals were stabilized and a precise ESR spectrum was obtained. Arrhenius plots of the second-order decay rate constants yield an activation energy of 5 kcal/mole. This suggests that the bimolecular termination reaction is controlled by the segmental motion of the grafted side chains.     

Extended Born-Green equation: A new approach for determining pair potentials in disordered systems

The Born-Green equation was tested using molecular dynamics data for liquid rubidium at 319 K. The unsatisfactory results of this equation for the pair potential are caused by the insufficient precision of the Kirkwood approximation for describing the triplet correlation function g₃(r,s,t). A more realistic ansatz for g₃(r,s,t) was employed in the formulation of an extended Born-Green equation. This new approach gives much better results for the potential than the simple Born-Green equation.     

Upper limit for DD production in pp interactions at C.M. energy of 55 GeV

From a search for e^±μ^± production at the CERN ISR an upper limit of 0.92 μb (95% confidence limit) has been inferred for σ·B_e·B_μ for the reaction $\text{p}\text{+}\text{p}\text{→}\text{D}\text{+}\text{D}\text{+}\text{X}\text{at}\text{√s}\text{of}\text{55}\text{GeV}$.