Lyapunov spectrum of a random Lorentz gas in a magnetic field

The Lyapunov exponents and the Kolmogorov Sinai entropy for 2- and 3-dimensional, dilute, random Lorentz gases in a magnetic field are calculated. The results are obtained by combining simple kinetic theory with geometric methods from dynamical systems theory. The Lyapunov exponents are explicitly calculated up to second order in the magnetic field.     

Force and torque on a sphere with electric dipole moment moving in a dielectric fluid in the presence of a uniform magnetic field

The torque exerted by a magnetic field on a sphere with permanent electric dipole moment moving steadily in a dielectric fluid is calculated to lowest order in the dipole moment. Hence the force exerted on a steadily rotating sphere with electric dipole moment is found by Onsager symmetry. The modification from the vacuum values of torque and force depends only on the slip parameter and the static dielectric constant of the fluid. It is suggested that for a macroscopic ferro electric sphere the calculated effects could be measured experimentally without great difficulty.     

Statistics in a Trilinear Interacting Stokes-Antistokes Boson System

The statistics of a system of four boson modes is treated with simultaneous Stokes-Antistokes interaction taking place. The time evolution is calculated in full quantum manner but in short time approximation. Mean photon numbers and correlations of second order are calculated. Antibunching can be found in the laser mode and in the system of Stokes and Antistokes mode.     

利用介质阻挡探针法测量大气压氦等离子体射流电子密度

分别利用电子的漂移速度和等离子体的传播速度计算了大气压下氦等离子体射流的电子密度。     

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The electron densities in the atmospheric pressure helium plasma were calculated by means of electron drift velocity and the jet velocity respectively. The electron velocity and jet velocity can be calculated by means of helium plasma jet current measured by a dielectric probe and plasma discharge current signal measured by voltage probes. The results show that the estimated electron densities of the helium plasma jet calculated from electron drift velocity and the jet velocity are in the order of 10 ¹¹ cm ^-3 and they increase with applied voltage. There is a little fluctuation in the value of the electron density along the jet axis of the plasma. This result is the same as the measured electron density in atmospheric pressure helium non-thermal plasma jet by using a Rogowski coil and a Langmuir probe. This is in one order lower than the electron density measured by microwave antenna.     

The Entropy of a Binary Hidden Markov Process

The entropy of a binary symmetric Hidden Markov Process is calculated as an expansion in the noise parameter ε. We map the problem onto a one-dimensional Ising model in a large field of random signs and calculate the expansion coefficients up to second order in ε. Using a conjecture we extend the calculation to 11th order and discuss the convergence of the resulting series     

Perturbation theory of a bound piezoelectric polaron

The shift of the ground state energy of a piezoelectric polaron bound in a Coulomb potential is calculated, numerically, to second order in the electron-phonon interaction for arbitrary strengths of the Coulomb potential. The results obtained are discussed so that some comments on the previous communications of other authors are drawn.     

Critical behavior of a non-uniform system

The correlation function of the local order parameter fluctuations in a non-uniform system with an interface is calculated by means of the mean field approximation. Some special limits are of particular interest and there the explicit forms of the correlation are given in three dimensions as well as in four dimensions.     

Adsorption of selenium wires in silicalite-1 zeolite: a first order transition in a microporous system

A tight binding grand canonical Monte Carlo simulation of the adsorption of selenium in silicalite-1 zeolite is presented. The calculated adsorption-desorption isotherms exhibit characteristic features of a first order transition, unexpected for adsorption in a microporous system with pore size of the order of 0.5 to 0.6 nm. We analyze this behavior as a result of the favored twofold coordinated chain structure of selenium that grows inside the complex three-dimensional microchannel network of silicalite. This analysis is confirmed by simpler calculations of a lattice gas-type model.     

Adsorption isotherm of a Lennard-Jones nitrogen in a carbon slitlike pore

A density functional perturbation approximation based both on second-order perturbation theory and on the pore average density has been proposed to study the adsorption hysteresis of nitrogen in a carbon slit pore. The main advantage of the present approximation is that it is computationally much simpler than the original density functional approximation based on the second-order perturbation theory of liquids, and can be applied to several model fluids confined in a strong external field in order to study their structural and thermodynamic properties. The calculated adsorption hysteresis for the confined Lennard-Jones nitrogen is in very good agreement with computer simulation, even if its accuracy slightly deteriorates for the desorption branch. The calculated equilibrium particle density distributions also compare well with computer simulations, and are better than those of a density functional theory based on the so-called mean-field approximation.     

Quantum corrections to the energy density of a homogeneous Bose gas

Quantum corrections to the properties of a homogeneous interacting Bose gas at zero temperature can be calculated as a low-density expansion in powers of , where is the number density and a is the S-wave scattering length. We calculate the ground state energy density to second order in . The coefficient of the correction has a logarithmic term that was calculated in 1959. We present the first calculation of the constant under the logarithm. The constant depends not only on a, but also on an extra parameter that describes the low energy scattering of the bosons. In the case of alkali atoms, we argue that the second order quantum correction is dominated by the logarithmic term, where the argument of the logarithm is ,and is the length scale set by the van der Waals potential. Received 2 February 1999     

Perturbative fragmentation of a vector color particle into bound states involving a heavy antiquark

Vector-particle fragmentation into possible S-wave bound states involving a heavy antiquark is considered for high-energy processes at high transverse momenta, and the relevant fragmentation function is calculated in the leading order of perturbative QCD for various patterns of the anomalous magnetic moment. One-loop equations describing the q ² evolution of the fragmentation-function moments that is caused by hard-gluon emission from the vector particle are derived. The integrated probabilities of fragmentation are obtained. The distribution of the bound state in the transverse momentum defined with respect to the fragmentation axis is calculated in the scaling limit.     

Latent heat of a homogeneously broadened two-mode laser

A homogeneously broadened two-mode laser exhibits metabistability and a first-order phase transition, with a discontinuous order parameter. The entropy is therefore discontinuous, and one can define a quantity that is analogous to the latent heat for a thermodynamic system. This is calculated for the laser, and shown to depend only weakly on the asymmetry of the laser.     

Theoretical analysis of ARUPS of a Si(100) surface at room temperature

ARUPS spectra of a Si(100) surface with disorder perpendicular to the dimer row are studied by the tight-binding method for the ensemble of surface buckled dimers. We assume order along the row. Results of ARUPS experiment on the surface at room temperature agree qualitatively with calculated results for disordered structure in which the distance to the next buckled dimer along the row and the height of the buckled dimer change alternately along the row. Peaks of two branches observed in a recent experiment at room temperature appear distinctly in calculated results as long as the short range order among the rows is not weak. The intensity of the two branches is very small compared to the other for conventional structure of the surface.     

Contribution to the muon anomaly from a set of eighth order diagrams

The value of the 18 diagrams of eoghth order, containing second order vacuum polarization and scattering of light-by-light insertions is calculated, giving a value of (111.1 ± 8.1) × (α/π)⁴. It agrees with the estimate given formerly by Lautrup.     

Freezing of a modulated liquid: The superionic-to-normal transition of strontium chloride

The anionic component in SrCl₂ near melting is treated as a modulated liquid in the periodic potential of the sublattice of cations. With decreasing temperature from the melting point, we find a diffuse disorder—order transition. The calculated behaviours of the order parameter and of thermodynamic properties approximate those observed for SrCl₂ across its superionic transition.     

Electron-optical characteristics of a combined electrostatic lens

The load characteristics of an electrostatic lens consisting of three coaxial cylinders are calculated. The lens is capable of focusing to one point both paraxial annular beams and annular beams away from the axis. In addition, it increases the intensity of a charged particle beam by roughly an order of magnitude compared with a commonly used single axisymmetric lens.     

Laws of formation of polar smectic phases under a frustrated interaction

The Landau theory of phase transitions with a two-component order parameter is used to systematically calculate the structures and phase diagrams of polar liquid crystals. Commensurate and incommensurate structures with a layer-type period form as a result of a frustration interaction. Phase diagrams are calculated when various short- and long-range interlayer interactions are sequentially introduced. As a result, the nature of formation of various structures is revealed. The calculated phase diagrams explain the formation of various phases, their temperature sequence (including so-called “unusual” sequence of phases), and the nature of forces responsible for the formation of a certain structure and the shape of a phase diagram.     

Structure Model of a One-Dimensional Disordered System with Short-Range Order

An ensemble of disordered linear chains is described by a probability density distribution without making use of the laws of thermodynamical equilibrium statistics. Short-range order is present in the system, because the position of an arbitrary particle depends on the location of the nearest neighbours. The nearest neighbour distance statistics is assumed to be of the Gaussian type. All correlation functions are calculated for finite and infinite systems. The superposition approximation is found to hold rigorously. The pair correlation is of fundamental importance for the system. The radial pair distribution function is investigated thoroughly. The configurational entropy of the system is calculated and discussed.     

Interpolating Hamiltonians for a stochastic-web map with quasicrystalline symmetry

A systematic Hamiltonian approximation scheme is developed for a stochastic-web map with fivefold quasicrystalline symmetry. Interpolating Hamiltonians are calculated up to tenth order in the control parameter a. The higher order Hamiltonians are used to provide bounds for closed invariant curves of the map, and to investigate the structural evolution of map's phase portrait for a相似文献