Dynamics of Coupled Quantum-Classical Oscillators

The dynamics of systems consisting of coupled quantum-classical oscillators is numerically investigated. It is shown that, under certain conditions, the quantum oscillator exhibits chaos. When the mass of the classical oscillator increases, the chaos will be suppressed; if the energy of the system and/or the coupling strength between the two oscillators increases, chaotic behaviour of the system appears. This result will be helpful to understand the probability of the emergence of quantum chaos and may be applied to explain the spectra of complex atoms qualitatively.     

Dynamics of multipionp¯ p annihilation

We construct a dynamical model to study the pion correlations in the 5 annihilation ofp¯ p at rest. For the resonant channels, the simplest Lorentz-invariant couplings have been used. It is found that, in addition to the Bose-Einstein correlations caused by the finite size of the source, the dynamical correlations from the channels with intermediate resonances are important for explaining the experimental two-pion correlation function. The reliability of two standard methods for pion interferometry is tested in our model.On leave from Institute of Nuclear Research, Academia Sinica, P.O. Box 800204, Shanghai 201800, China     

Dynamics of Maxwell’s pendulum

The stability of motion of Maxwell’s pendulum is investigated in a uniform gravity field. By means of several canonic transforms of the equations of pendulum motion and the method of the surfaces of Poincaré sections, the problem is reduced to investigation of the immobile-point stability retaining the area of mapping of the plane into itself. In the space of dimensionless parameters, the stability and instability regions are singled out.     

Excitation Dynamics in High-precision Two-photon Spectroscopy

High-precision two-photon spectroscopy of hydrogen and hydrogenlike systems allows for stringent tests of bound state QED and provides a laboratory tool to probe a possible drift of fundamental constants. On the current level of accuracy in determining the hydrogen 1S-2S absolute frequency , it is crucial to take into account the time-dependent nature of the excitation process, in order to correctly describe the experimental observations. In particular, the ionization of the excited state by absorption of a single additional laser photon restricts the interaction time in the spectroscopy experiment and prevents the system from evolving into a populated steady state.     

Impact of Viscosity on DNA Dynamics

We study the influence of viscosity on DNA dynamics. By employing the nonlinear Peyrard-Bishop-Dauxois （PBD） model, it is shown that the DNA dynamics can be explained by a solution of a complex nonlinear Schrǒdinger equation （CNLSE）. This is the nonlinear Schrǒdinger equation （NLSE） with a nonlinear parameter being a complex number. We compare real and imaginary parts of this nonlinear parameter and show that the latter one should not be negligible, which means that the CNLSE should be solved numerically,     

Minimal Braid in Applied Symbolic Dynamics

Based on the minimal braid assumption, three-dimensionai periodic flows of a dynamical system are reconstructed in the case of unimodai map, and their topologicai structures are compared with those of the periodic orbits of the R6ssler system in phase space through the numerical experiment. The numerical results justify the validity of the minimai braid assumption which provides a suspension from one-dimensional symbolic dynamics in the Poincare section to the knots of three-dimensionai periodic flows.     

Dynamics of Ξ-hyperon production on nucleon

A phenomenological model of Ξ-hyperon production from nucleons by antikaons is developed. The model successfully reproduces available experimental data on integral and differential cross sections of the reaction in the different charge channels at the center-of-mass energies from the threshold up to 3.2 GeV. It is shown that the baryonic (u-channel) exchange is the dominant reaction mechanism.     

Influence of Morse Potential on DNA Dynamics

Based on the Peyrard-Bishop-Dauxois （i.e. the extended Peyrard-Bishop） model of DNA dynamics, the transversal hydrogen interaction is modelled by Morse potential and the impact of the Morse parameters on the DNA dynamics is investigated. In particular, we show how modulation of the signal, moving through the DNA chain, depends on those parameters. It is also shown that the DNA dynamics represents the interplay between dispersion and nonlinearity. Finally, we discuss the values of coupling constants κ and K.     

Gold Nanobelt Reorientation by Molecular Dynamics Simulation

The embedded atom method is used to study the structure stability of gold nanobelt. The Au nanobelts have a rectangular cross-section with （100） orientation along the x^-,γ- and z-axes. Free surfaces are used along the x- and y-directions, and periodic boundary condition is used along z-direction. The simulation is performed at different temperatures and cross-section sizes. Our results show that the structure stability of the Au nanobelts depends on the nanobelt size, initial orientation, boundary conditions and temperature. A critical temperature exists for Au nanobelts to transform from initial （100） nanobelt to final （110） nanobelt. The mechanism of the reorientation is the slip and spread of dislocation through the nanobelt under compressive stress caused by tensile surface-stress components.     

Dynamics of k-essence in loop quantum cosmology

In this paper,we study the dynamics of k-essence in loop quantum cosmology(LQC).The study indicates that the loop quantum gravity(LQG)effect plays a key role only in the early epoch of the universe and is diluted in the later stages.The fixed points in LQC are basically consistent with those in standard Friedmann-Robertson-Walker(FRW)cosmology.For most of the attractor solutions,the stability conditions in L Q C are in agreement with those for the standard FRW universe.For some special fixed points,however,tighter constraints are imposed thanks to the LQG effect.     

Copper Nanobelt Reorientation by Molecular Dynamics Simulation

Atomic simulations using embedded atom method （EAM） are performed for Cu （100） nanobelts to study the structural and mechanical behaviour. Cu （100） nanobelts are along[001] taken as the z-axis and have a rectangular cross section in the x - y plane, with [100] and [010] taken as x and y axes. The periodic boundary is used along the z-axis to simulate an infinitely long nanobelt, and other surfaces are free. The simulations are carried out under the mechanical loading with an elongation strain rate of 8.0×10^8 s^-1 along the z-axis. The results show that the nanobelt undergoes a transition from the initial structure with a （100） axis and {100} lateral surfaces to a new structure with the （112） as the z-axis and the lateral surfaces are {111} and {110} respectively, instead of the original {100} surfaces. The mechanism of the structural transition is ascribed to the dislocation propagation through the nanobelt under the external stresses.     

Extension of Isospin Dependent Quantum Molecular Dynamics

Isospin dependent molecular dynamics (IQMD) has been used with success for studying isospin effects in heavy ion collisions at intermediate energies[1,2]. However, this model meets difficulty to study heavy ion collisions at low energies near Coulomb barrier since unsuitable dealing with the deformation, such as surface term induced by deformation during approaching projectile and target, which is not important at high energies, and it results in the calculated cross sections with IQMD which are much smaller than the experimental data at low energies. In this report, we propose a new method in which the surface term in the mean field is included in a proper way, the switch function method.     

Two-Dimensional Self-Propelled Fish Motion in Medium： An Integrated Method for Deforming Body Dynamics and Unsteady Fluid Dynamics

We present （1） the dynamical equations of deforming body and （2） an integrated method for deforming body dynamics and unsteady fluid dynamics, to investigate a modelled freely self-propelled fish. The theoretical model and practical method is applicable for studies on the general mechanics of animal locomotion such as flying in air and swimming in water, particularly of free self-propulsion. The present results behave more credibly than the previous numerical studies and are close to the experimental results, and the aligned vortices pattern is discovered in cruising swimming.     

Constrained Correlation Dynamics of QED in Canonical Form(Ⅱ)Equal Time Limit and Two-Body Correlation Dynamics

The equations of motion for multi-time correlation Green's functions are transformed into those for equal-time correlation Green's functions,which include the equations of motion for electron's and photon's density matrices as well as vertex functions.In two-body correlation truncation approximation,we present the explicit expressions for the equations of motion,Gauss law and Ward identities explicitly.     

Local Events and Dynamics on Weighted Complex Networks

We examine the weighted networks grown and evolved by local events, such as the addition of new vertices and links and we show that depending on frequency of the events, a generalized power-law distribution of strength can emerge. Continuum theory is used to predict the scaling function as well as the exponents, which is in good agreement with the numerical simulation results. Depending on event frequency, power-law distributions of degree and weight can also be expected. Probability saturation phenomena for small strength and degree in many real world networks can be reproduced. Particularly, the non-trivial clustering coefficient, assortativity coefficient and degree-strength correlation in our model are all consistent with empirical evidences.     

Quantum Dynamics of One—Dimensional Nanocrystalline Solids

A novel ballistic-nonballistic dynamic transition in one-dimensional nanocrystalline solids is found upon varying the strength of the composition modulation and the grain-boundary effect.This can contribute to the understanding of the strange electronic transport porperties of nanostructured systems.     

Entanglement Dynamics in Typical Local- and Normal-Mode Molecules

The entanglement dynamics of two stretching vibrations in theoretically typical local- and normal-mode molecules and realistic molecules H2 O and SO2 in an algebraic model is studied in terms of the reduced-density linear entropy with initial entangled states taken to be two-mode squeezed vacuum states. It is shown that the behaviour of the entropy in theoretically typical molecules appears to be more regular than that in realistic ones, and that the entropy becomes irregular as the amplitude of two-mode squeezed vacuum states increases. For initial states with a small amplitude, it is demonstrated that the periodicity and the “classical” beat phenomenon of the entropy occur with the beat in theoretically typical molecules being more regular than that in realistic molecules H2O and SO2.     

Sandpile Dynamics Driven by Degree on Scale-Free Networks

We introduce a sandpile model driven by degree on scale-free networks, where the perturbation is triggered at nodes with the same degree. We numerically investigate the avalanche behaviour of sandpile driven by different degrees on scale-free networks. It is observed that the avalanche area has the same behaviour with avalanche size. When the sandpile is driven at nodes with the minimal degree, the avalanches of our model behave similarly to those of the original Bak-Tang-Wiesenfeld （BTW） model on scale-free networks. As the degree of driven nodes increases from the minimal value to the maximal value, the avalanche distribution gradually changes from a clean power law, then a mixture of Poissonian and power laws, finally to a Poisson-like distribution. The average avalanche area is found to increase with the degree of driven nodes so that perturbation triggered on higher-degree nodes will result in broader spreading of avalanche propagation.     

Dynamics of semi-infinite quantum spin chains atT=∞

Time-dependent spin autocorrelation functions and their spectral densities for the semi-infinite one-dimensionals=1/2 XY and XXZ models atT= are determined in part by rigorous calculations in the fermion representation and in part by the recursion method in the spin representation. Boundary effects yield valuable new insight into the different dynamical processes which govern the transport of spin fluctuations in the two models. The results obtained for theXXX model bear the unmistakable signature of spin diffusion in the form of a squareroot infrared divergence in the spectral density.From April 1 to September 30, 1992 also at Institut für Physik Universität Augsburg, W-8900 Augsburg, Federal Republic of Germany     

Dynamics of η→3π0 decay

The η→3π⁰ decay was studied with the SND detector at the VEPP-2Me ⁺ e ^? collider. The parameter that describes deviation of the Dalitz plot of events from a uniform distribution was found to be α=?0.010±0.021±0.010.