共查询到20条相似文献,搜索用时 203 毫秒
1.
将自由状态下呈弹道扩散的非各态历经系统置于周期场中,进而将非各态历经布朗运动分为两类.第一类是阻尼核的Laplace变换的低频为零的系统,当温度远大于势垒高度时,系统平均能量的动能部分依赖粒子的初始速度分布;随温度降低,系统的各态历经性得到恢复.然后将第一类系统的稳定速度变量作为一个内部噪声,再去驱动一个自由布朗粒子,则阻尼核的Laplace变换在零频时为无穷大.结果发现,粒子扩散系数随温度的增加而趋于零,显示一种经典局域化特征,系统的渐进分布依赖于初始坐标分布.这是第二类非各态历经性运动,不能通过外加势而恢复.
关键词:
非各态历经
非Markov布朗运动
扩散系数
噪声谱 相似文献
2.
研究了在对称双势阱玻色-爱因斯坦凝聚体系粒子间相互作用项上外加周期调制而引起的系统动力学相变,特别地研究了该系统通向混沌的相变过程.发现在一定驱动参数下,当外加调制频率与系统固有频率达到共振时,相平面会出现不稳定性现象,即混沌.在混沌区域,粒子在各量子态随机分布,平均布居数差在零附近波动.特别地,研究表明,混沌现象的出现可以用量子纠缠熵来表征,混沌现象出现时,两种平均纠缠熵都趋于它们的最大值.
关键词:
玻色-爱因斯坦凝聚
双势阱
混沌
纠缠熵 相似文献
3.
考虑一个由两种类粒子组成的系统,同种类粒子相遇时发生不可逆的聚集反应;不同种类的粒子相遇时,则发生不可逆的完全湮没反应.利用Mont-Carlo模拟各种参数条件下的粒子聚集-完全湮没竞争过程,分析了聚集速率、湮没速率以及初始浓度分布对系统动力学行为的影响.模拟结果表明:1)粒子大小分布总是满足一定的标度律;2)当两种粒子的聚集速率都等于湮没速率的2倍时,粒子大小分布的标度指数与粒子初始浓度分布有关;3)其余情况下,标度指数则取决于反应速率的相对大小.此外,当两种粒子的聚集速率都大于或等于湮没速率的两倍,系统的所有粒子将完全湮没;当且仅当至少一种粒子的聚集速率小于湮没速率的两倍,聚集速率较小的那一种粒子才可能最终保存下来.模拟结果与已报道的理论分析结果符合得较好. 相似文献
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利用Born-Oppenheimer近似研究了零温时耗散两态系统的动力学特性.在不同环境谱分布下,给出了两态之间的跃迁几率随时间的变化.数值结果表明:当环境的谱分布为Ohmic形式时,跃迁几率是一个衰减的函数;而当谱分布为随机取值时,跃迁几率具有“量子跳跃”的特性.与之相对比,我们还给出了当把环境等价成无穷多个谱振子的集合时,跃迁几率随时间的变化. 相似文献
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本文讨论零质量玻色场φ(x)在动量空间的零频部分,它不是动量趋于零时的极限,所以并不代表粒子的产生和湮灭算符。由于正则量子化得到一连续量子数,因此所有物理态都不能归一。真空变成一个无穷宽能带中的任意一个态。当φ(x)是厄米场时,真空并不存在简并,因此没有真空自发破缺;当φ(x)是复数场时,每一真空都是无穷地分立简并,因此也没有连续对称的自发破缺。利用这些态容易验证 Goldstone 定理证明中所插入的零动量零能量中间态并非代表不同数目的 Goldstone 粒子的相干迭加,也不一定与原来的真空态正交。文章亦讨论了φ(x)→φ(x)+η的生成元,它作用在φ(x)上的真空平均值及作用在真空态上的结果。 相似文献
10.
在扩散限制凝聚模型的基础上引入粒子的自旋自由度(包括自旋向上和向下),并假设粒子间存在幂次Ising磁相互作用,采用Monte Carlo方法研究了在不同相互作用力程情况下磁性粒子的分形生长规律.模拟结果表明,当粒子间以反铁磁方式耦合时,凝聚体中的粒子自旋交替凝聚.当粒子间以铁磁方式耦合时,凝聚体中粒子的自旋分布与相互作用力程有关:对于短程作用系统,凝聚体中存在大小不同的自旋畴块,即为铁磁生长;而对于长程相互作用系统,凝聚体中的自旋出现反常分布,即中心区域是近似反铁磁生长的结构,其外围后续生长的粒子却保持
关键词:
幂次相互作用
扩散限制凝聚模型
自旋 相似文献
11.
Hydrodynamic Limit of Condensing Two-Species Zero Range Processes with Sub-critical Initial Profiles
Nicolas Dirr Marios G. Stamatakis Johannes Zimmer 《Journal of statistical physics》2017,168(4):794-825
Two-species condensing zero range processes (ZRPs) are interacting particle systems with two species of particles and zero range interaction exhibiting phase separation outside a domain of sub-critical densities. We prove the hydrodynamic limit of nearest neighbour mean zero two-species condensing ZRP with bounded local jump rate for sub-critical initial profiles, i.e., for initial profiles whose image is contained in the region of sub-critical densities. The proof is based on H.T. Yau’s relative entropy method, which relies on the existence of sufficiently regular solutions to the hydrodynamic equation. In the particular case of the species-blind ZRP, we prove that the solutions of the hydrodynamic equation exist globally in time and thus the hydrodynamic limit is valid for all times. 相似文献
12.
B. Waclaw Z. Burda W. Janke 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(4):565-570
We study statistical properties of a zero-range process (ZRP) on random networks.We derive an analytic expression for the
distribution of particles (also called node occupation distribution)in the steady state of the ZRP in the ensemble of uncorrelated
random graphs. We analyze the dependence of this distribution on the node-degree distribution.In particular, we show that
when the degree distribution is tuned properly, one can obtainscale-free fluctuations in the distribution of particles.Such
fluctuations lead to a power law in the distribution of particles, just like in the ZRP with the hopping rate u(m) = 1+b/mon
homogeneous graphs. 相似文献
13.
Considering the heterogeneity of individuals’ influence in the real world, we introduce a preferential selection mechanism to evolutionary games (the Prisoner’s Dilemma Game and the Snowdrift Game) on scale-free networks and focus on the cooperative behavior of the system. In every step, each agent chooses an individual from all its neighbors with a probability proportional to kα indicating the influence of the neighbor, where k is the degree. Simulation results show that the cooperation level has a non-trivial dependence on α. To understand the effect of preferential selection mechanism on the evolution of the system, we investigate the time series of the cooperator frequency in detail. It is found that the cooperator frequency is greatly influenced by the initial strategy of hub nodes when α>0. This observation is confirmed by investigating the system behavior when some hub nodes’ strategies are fixed. 相似文献
14.
We study the phenomena of preferential linking in a large-scale evolving online social network and find that the linear preference holds for preferential creation,preferential acceptance,and preferential attachment.Based on the linear preference,we propose an analyzable model,which illustrates the mechanism of network growth and reproduces the process of network evolution.Our simulations demonstrate that the degree distribution of the network produced by the model is in good agreement with that of the real network.This work provides a possible bridge between the micro-mechanisms of network growth and the macrostructures of online social networks. 相似文献
15.
We study the aspects of diffusion for the case of zero range process interaction on scale-free networks, through statistical quantities such as the mean first passage time, coverage, mean square displacement etc., and pay attention to how the interaction, especially the resulted condensation, influences the diffusion. By mean-field theory we show that the statistical quantities of diffusion can be significantly reduced by the condensation and can be figured out by the waiting time of a particle staying at a node. Numerical simulations have confirmed the theoretical predictions. 相似文献
16.
Castro EV Grushin AG Valenzuela B Vozmediano MA Cortijo A de Juan F 《Physical review letters》2011,107(10):106402
We propose a simple method for obtaining time reversal symmetry (T) broken phases in simple lattice models based on enlarging the unit cell. As an example we study the honeycomb lattice with nearest neighbor hopping and a local nearest neighbor Coulomb interaction V. We show that when the unit cell is enlarged to host six atoms that permits Kekulé distortions, self-consistent currents spontaneously form creating nontrivial magnetic configurations with total zero flux at high electron densities. A very rich phase diagram is obtained within a variational mean field approach that includes metallic phases with broken time reversal symmetry (T). The predominant (T) breaking configuration is an anomalous Hall phase, a realization of a topological Fermi liquid. 相似文献
17.
We study a zero range process on scale-free networks in order to investigate how network structure influences particle dynamics. The zero range process is defined with the rate p(n) = n(delta) at which particles hop out of nodes with n particles. We show analytically that a complete condensation occurs when delta < or = delta(c) triple bond 1/(gamma-1) where gamma is the degree distribution exponent of the underlying networks. In the complete condensation, those nodes whose degree is higher than a threshold are occupied by macroscopic numbers of particles, while the other nodes are occupied by negligible numbers of particles. We also show numerically that the relaxation time follows a power-law scaling tau approximately L(z) with the network size L and a dynamic exponent z in the condensed phase. 相似文献
18.
We explore the nature of the transition to the Fulde-Ferrell-Larkin-
Ovchinnikov superfluid phases
in the low temperature range in two dimensions, for the simplest
isotropic BCS model. This is done by applying the Larkin-Ovchinnikov
approach to this second order transition. We show that there is a
succession of transitions toward ever more complex order parameters
when the temperature goes to zero. This gives rise to a cascade with, in
principle, an infinite number of transitions. Except for one case, the
order parameter at the transition is a real superposition of cosines with
equal weights. The directions of these wavevectors are equally spaced
angularly, with a spacing which goes to zero when the temperature goes
to zero. This singular behaviour in this T = 0 limit is deeply linked to
the two-dimensional nature of the problem. 相似文献
19.
Folklore suggests that the split Lie-like operators of a complex partial differential equation are symmetries of the split
system of real partial differential equations. However, this is not the case generally. We illustrate this by using the complex
heat equation, wave equation with dissipation, the nonlinear Burgers equation and nonlinear KdV equations. We split the Lie
symmetries of a complex partial differential equation in the real domain and obtain real Lie-like operators. Further, the
complex partial differential equation is split into two coupled or uncoupled real partial differential equations which constitute
a system of two equations for two real functions of two real variables. The Lie symmetries of this system are constructed
by the classical Lie approach. We compare these Lie symmetries with the split Lie-like operators of the given complex partial
differential equation for the examples considered. We conclude that the split Lie-like operators of complex partial differential
equations are not in general symmetries of the split system of real partial differential equations. We prove a proposition
that gives the criteria when the Lie-like operators are symmetries of the split system. 相似文献