EZ模型中的有限尺寸效应

研究EZ模型中的有限尺寸效应.当经纪人数目N足够大及发生交易的概率a1/N,发现有限尺 寸效应是重要的.此时,系统几乎变成包含所有经纪人的单一集团.而对较小集团,尺寸分布 仍然服从幂函数律,但是指数因涨落效应而改变.但当a1/N时,可以论证涨落效应不重要 ,因而平均场理论是严格成立的.关键词：EZ模型有限尺寸效应涨落平均场理论     

一混沌模型的系综模拟研究

本文用随机模拟方法研究了一化学混沌模型的介观动力学。对该混沌模型的系综模拟发现 ,在这种不稳定运动中存在强烈的内部涨落 ,然而由于混沌运动整体上的稳定性 ,使得系统中的代表点被限制在混沌吸引子上 ,并且每个代表点形成的随机轨道很好地保持了确定性混沌吸引子的基本特性     

量子气体中的输运行为

输运测量是了解物质性质的一个重要手段.本文简单介绍最近在量子气体中实现的输运实验及其主要结论,包括在类似于介观物理器件中的Landauer输运和强相互作用费米气体中的自旋输运行为.我们着重讨论自旋动力学的特殊性以及其由于全同粒子相互作用所导致的特殊自旋扩散流的形式.     

体温计模型的临界行为

提出一个可用离散朗之万方程描述的体温计模型.该体温计的特点是其温度示数只能随外界温度的升高而上升,当外界温度降低时,其示数却不能下降.根据体温计示数这种只升不降的特点,定义了“停顿”事件.用随机行走的理论解析地推导了停顿时间分布函数数值模拟和解析结果都显示这种分布函数呈幂律形式D(s)∝s^-ξ,揭示出在这一过程中所表现出的临界性.关键词：     

红外辐射场理论模拟中的普适性模型研究

在现有海面目标红外辐射场理论建模工作的基础上建立了具有普适性意义的海面目标红外辐射场理论建模通用框架,重点对建立目标的几何构型、适用于各种微元的物理模型、及通用的三维数据场可视化这三个问题进行了叙述。所得结果不仅对海面各种目标红外辐射场的计算机模拟研究具有普遍的意义,且对空中、陆地及其他场景中目标的红外辐射场理论建模研究也有一定的借鉴作用。     

La0.7-xDyxSr0.3MnO3中的相分离和输运行为

通过测量样品的M-T曲线、 M-H曲线、 ESR曲线、ρ-T曲线和MR-T曲线, 研究了Dy掺杂(0.0≤x≤0.30)对La0.7Sr0.3MnO3磁电性质的影响. 实验结果表明 在TC处所有样品都经历了顺磁到铁磁的转变; 当T＜TC时, 掺杂样品进入自旋团簇玻璃态, 低温时显示出反铁磁性; x=0.20时, 样品在TC以上温区发生相分离; Dy掺杂引起的磁结构变化将导致CMR效应.     

推广的磁通活脱钉模型（EMTAD）中的中值能量问题

本文详细论证了推广的磁通热激活脱钉模型与一维周期势中布朗运动稳态解的一致性地利用中值定理引入截止能量ＥＣ可能带来的误差作了估计。     

有限维希尔伯空间谐振子的振幅消相干及其推广

为了研究二态体系和谐振子体系在振幅消相干方面的联系,我们研究有限维希尔伯空间谐振子的振幅消相干性质,然后推广到能谱等间隔体系,发现这些体系虽然在某些方面差别很大,但是由于体系的能谱等间隔这个特点,使得它们的振幅消相干性质完全类似.     

等同双原子Jaynes-Cummings模型的量子特性及系统光谱

在全量子理论的背景下提出两个二能级原子分别与一单模腔场相互作用的系统模型,利用量子主方程和数值模拟计算等方法,研究该体系中腔场平均光子数、Mandel'sQ因子及二阶量子相关度在非稳态时的变化规律。此外,对体系中原子及腔场中光谱结构进行了分析。结果表明:减小腔场耗散系数,增大原子间耦合系数,体系量子特性愈加明显。体系光谱呈现出Mollow三重峰结构,且原子辐射谱强度远大于腔场辐射谱强度。当原子跃迁频率与腔场跃迁频率为近共振时,Mollow峰值为三峰中最大值。此外,增大原子与腔场间耦合系数,可增大原子光谱的中峰强度;而增大腔场光谱的中峰强度,则需减小原子与腔场间耦合系数。

     

28.7MeV/u的 14，16，18 O+7，9Be反应中的同位素分布研究

用同位旋相关的Boltzmann-Langevin方程研究了在入射能量为28.7MeV/u下,不同弹核^14O,^16O和^18O轰击不同靶核^7Be和^9Be的反应,计算了生成碎片的产生截面,发现用丰中子（缺中子）炮弹或丰中子（缺中子）靶进行反应,所得到的产物均有丰中子（缺中子）的碎片出现。同位素分布宽度和峰位与入射体系密切相关,产生碎片的电荷数越接近入射弹核的电荷数,则同位素分布的宽度越大,峰位偏离β稳定线值越远,其同位旋效应越明显。。     

On the equivalence of some exact master equations

In this note we show the equivalence of two procedures for obtaining exact, convolutionless master equations.     

Homogeneous Generalized Master Equations

It is shown that the method proposed in V. F. Los [J. Phys. A: Math. Gen. 34: 638–6403 (2001)], which allows for turning the inhomogeneous time-convolution generalized master equation (TC-GME) into homogeneous (while retaining initial correlations) time-convolution generalized master equation (TC-HGME) for the relevant part of a distribution function, is fully applicable to the quantum case and to the time-convolutionless GME (TCL-GME). It is demonstrated by rederiving the TC-HGME and showing that it works in both the classical and quantum physics cases. The time-convolutionless HGME (TCL-HGME) retaining initial correlations, which is formally the same for both the classical and quantum physics, has also been derived. Both the TC-HGME and TCL-HGME are exact equations applicable on any timescale and allow for consecutive treating the initial correlations and collisions on the equal footing. A new equation for a momentum distribution function retaining initial correlations has been obtained in the linear in the density of quantum particles approximation. Connection of this equation to the quantum Boltzmann equation is discussed.     

稠密共振介质中近偶极-偶极相互作用的局域场效应

为研究存在由近偶极-偶极相互作用诱导的局域场效应时超短强激光脉冲与稠密共振介质相互作用的特性,采用光与物质相互作用的半经典理论,建立了稠密二能级体系中考虑原子间近偶极-偶极相互作用的修正光学Bloch方程,并用四阶Runge-Kutta法数值求解了该方程。研究结果表明:局域场效应对稠密二能级体系中Bloch矢量的瞬态相干过程和稳态性质都具有强烈的调制作用。并由此提出了调控稳态粒子数布居的两种方案。     

Decay of correlations. IV. Necessary and sufficient conditions for a rapid decay of correlations

We considerN-particle systems whose probability distributions obey the master equation. For these systems, we derive the necessary and sufficient conditions under which the reducedn-particle (n) probabilities also obey master equations and under which the Ursell functions decay to their equilibrium values faster than the probability distributions. These conditions impose restrictions on the form of the transition rate matrix and thus on the form of its eigenfunctions. We first consider systems in which the eigenfunctions of theN-particle transition rate matrix are completely factorized and demonstrate that for such systems, the reduced probabilities obey master equations and the Ursell functions decay rapidly if certain additional conditions are imposed. As an example of such a system, we discuss a random walk ofN pairwise interacting walkers. We then demonstrate that for systems whoseN-particle transition matrix can be written as a sum of one-particle, two-particle, etc. contributions, and for which the reduced probabilities obey master equations, the reduced master equations become, in the thermodynamic limit, those for independent particles, which have been discussed by us previously. As an example of suchN-particle systems, we discuss the relaxation of a gas of interacting harmonic oscillators.Supported in part (grants to D.B. and K.E.S.) by the Advanced Research Projects Agency of the Department of Defense as monitored by the U.S. Office of Naval Research under Contract N00014-69-A-0200-6018, and in part (grant to I.O.) by the National Science Foundation.     

Relaxation problem with a quadratic noise: Analysis

The properties of a linear differential equation with an additive quadratic noise are analyzed. The graphs of the probability distribution of the process are presented for various values of the noise strength and the damping constant. The time evolution of the distribution is also shown. An infinitesimal generator of the evolution operator of the process is constructed. A diffusion-type approximation is considered and a comparison of the exact solution with the approximate solution is carried out.This paper is dedicated to the memory of Prof. A. Pawlikowski.     

A comment on chemical Langevin equations

It is noted that the diffusion Langevin stochastic sources in chemical reaction-diffusion theories should really arise from a stochastic source term added to the deterministic form of Fick's law. This gives rise to results for correlation functions which agree with those from stochastic master equations provided parameters are appropriately chosen.Some authors use the term Langevin force. Sinceg _i(x,t) is dimensionally not a force, we shall eschew this dangerous terminology.     

Production mechanism of superheavy nuclei in massive fusion reactions

Within the concept of the dinuclear system (DNS), a dynamical model is proposed for describing the formation of superheavy nuclei in complete fusion reactions by incorporating the coupling of the relative motion to the nucleon transfer process. The capture of two heavy colliding nuclei, the formation of the compound nucleus and the de-excitation process are calculated by using an empirical coupled channel model, solving a set of microscopically derived master equations numerically and applying statistical theory, respectively. Fusion-fission reactions and evaporation residue excitation functions of synthesizing superheavy nuclei (SHN) are investigated systematically and compared them with available experimental data. The possible factors that affecting the production cross sections of SHN are discussed in this workshop.     

供课堂用的大学物理演示软件

介绍了大学物理原理演示软件的内容、研制路线、功能及运行条件．