共查询到20条相似文献,搜索用时 15 毫秒
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T. Dobrowolski 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(2):269-271
The production of topological defects during a quench in a φ4 model is investigated. The influence of a spatially correlated noise on defect production in two and three dimensions is
demonstrated.
Received 28 August 2001 / Received in final form 11 February 2002 Published online 2 October 2002
RID="a"
ID="a"Paper supported in part by ESF “COSLAB” Programme
RID="b"
ID="b"e-mail: sfdobrow@kinga.cyf-kr.edu.pl 相似文献
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The measurement of very small light forces has wide applications in many fields of physics. A common measurement method for small force detection is the determination of changes in the dynamic behavior of mechanical oscillators, either in amplitude or in frequency. The detection of slowly varying forces mostly requires long period oscillators, such as a torsion pendulum. We demonstrate the application of a macroscopic, low-noise, torsion balance oscillator for the detection of radiation pressure forces at the femto-Newton level. The system is "precooled" (removing excess seimic noise) to be only thermal noise limited. The demonstrated force sensitivity reaches the thermal limit. 相似文献
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以电耦合的Terman-Wang小世界神经元网络系统为研究对象, 研究了空间关联白噪声影响下神经元网络系统的同步动力学. 首先将动力学平均场近似理论扩展到受空间关联白噪声影响下的小世界网络系统中, 将描述网络系统动力学演化的2N维随机微分方程简化为11个确定性的矩微分方程. 其次, 基于动力学平均场近似理论所推导的矩方程, 讨论了空间关联噪声、网络结构参数对神经元网络系统同步动力学的关键影响, 发现较大的噪声空间关联系数、耦合强度及节点平均度均对神经元网络系统同步放电具有积极作用. 进一步地, 利用计算机仿真数值模拟原神经元网络系统的同步动力学, 并与基于动力学平均场近似理论所得到的结果进行比较, 发现二者具有较好的一致性. 相似文献
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We study the quantum discord dynamics of two noninteracting qubits that are, respectively, subject to classical noise. The results show that the dynamics of quantum discord are dependent on both the coupling between the qubits and classical noise, and the average switching rate of the classical noise. In the weak-coupling Markovian region, quantum discord exhibits exponent decay without revival, and can be well protected by increasing the average classical noise switching rate. While in the strong-coupling non-Markovian region, quantum discord reveals slowly decayed oscillations with quick revival by decreasing the average switching rate of the classical noise. Thus, our results provide a new method of protecting quantum discord in a two-qubit system by controlling the coupling between the qubits and classical noise, and the average switching rate of the classical noise. 相似文献
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We consider quantum error correction of quantum noise that is created by a local interaction of qubits with a common bosonic bath. The possible exchange of bath bosons between qubits gives rise to spatial and temporal correlations in the noise. We find that these kinds of noise correlations have a strong negative impact on quantum error correction. 相似文献
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The effects of correlation between additive and multiplicative noises on the symmetry of an asymmetric bistable system are investigated. The steady-state probability distribution function of the system was calculated by using analytical and numerical methods. Results indicate that i) for the case of positive correlation between noises, as the correlation strength between additive and multiplicative noises, λ, increases, the symmetry of the system is restored; ii) for the case of negative correlation between noises, as the absolute value of λ increases, the symmetry of the system is destroyed; and iii) the analytic prediction agrees well with the stochastic simulation result. 相似文献
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研究了由关联乘性色噪声及加性白噪声驱动的非对称双稳系统中势阱的非对称性及噪声对系统两个方向平均首次穿越时间的影响. 首先利用一致有色噪声近似推导了系统的稳态概率密度的表达式,根据最速下降法推导了平均首次穿越时间的表达式. 数值结果表明:势阱的非对称性对两个方向的平均首次穿越时间的影响是不同的;由于噪声的关联性,即使对于关联乘性色噪声及加性白噪声驱动的对称双稳系统,两个方向的平均首次穿越时间也不再相等;在lnT+-r和lnT-关键词:
平均首次穿越时间
非对称双稳系统
乘性色噪声
加性白噪声 相似文献
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Mean first-passage time of an asymmetric bistable system driven by colour-correlated noise 下载免费PDF全文
In this paper, the effect of every parameter (including p, q, r,
\la, \tau) on the mean first-passage time (MFPT) is investigated in
an asymmetric bistable system driven by colour-correlated noise. The
expression of MFPT has been obtained by applying the steepest-descent
approximation. Numerical results show that (1) the intensity of
multiplicative noise p and the intensity of additive noise q play
different roles in the MFPT of the system, (2) suppression appears on
the curve of the MFPT with small \la (e.g. \la<0.5) but there is
a peak on the curve of the MFPT when \la is big (e.g. \la >0.5),
and (3) with different values of r (e.g. r=0.1, 0.5, 1.5), the
effort of \tau on the MFPT is diverse. 相似文献
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H.K. Janssen U.C. Täuber E. Frey 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):491-511
We investigate the Kardar-Parisi-Zhang (KPZ) equation in d spatial dimensions with Gaussian spatially long-range correlated noise -- characterized by its second moment -- by means of dynamic field theory and the renormalization group. Using a stochastic Cole-Hopf transformation we derive
exact exponents and scaling functions for the roughening transition and the smooth phase above the lower critical dimension . Below the lower critical dimension, there is a line marking the stability boundary between the short-range and long-range noise fixed points. For , the general structure of the renormalization-group equations fixes the values of the dynamic and roughness exponents exactly,
whereas above , one has to rely on some perturbational techniques. We discuss the location of this stability boundary in light of the exact results derived in this paper, and from results known in the literature. In particular, we conjecture
that there might be two qualitatively different strong-coupling phases above and below the lower critical dimension, respectively.
Received 5 August 1998 相似文献
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Stochastic resonance (SR) induced by the bounded noise in an asymmetric bistable system is investigated. Based on stochastic simulation, the signal power amplification SPA is derived for the case of the additive modulated signal. The simulation results indicate that: (1) the SR phenomenon is weakened by the asymmetry of the system; (2) increasing the frequency ω restricts the SR of the system; (3) there is an optimum value of amplitude A matching the strongest SR phenomenon. 相似文献
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The effect of noise on the output parameters of a three-mirror system is investigated under the conditions when one of the cavities is filled with an amplifying medium and the other is empty. For weak coupling between the cavities, the amplitude noise at the outlet of the empty cavity decreases sharply, and the emission band becomes narrower than the natural bandwidth. Expressions are given for analyzing a more general problem on the statistical characteristics of laser radiation emitted by the three-mirror system with a weak noise. 相似文献
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W.-C. Xie 《Journal of sound and vibration》2003,263(3):593-616
The moment Lyapunov exponents of a two-dimensional system under bounded noise parametric excitation are studied in this paper. The method of regular perturbation is applied to obtain weak noise expansions of the moment Lyapunov exponent, Lyapunov exponent, and stability index in terms of the small fluctuation parameter. 相似文献
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In this paper, the stationary probability distribution (SPD) function and the mean first passage time (MFPT) are investigated in a tumor growth model driven by non-Gaussian noise which is introduced to mimic random fluctuations in the levels of the immune system. Results demonstrate the different transitions induced by the strength of non-Gaussian noise under different immune coefficients and the dual roles of non-Gaussian noise in promoting host protection against cancer and in facilitating tumor escape from immune destruction. Additionally, it can be discovered that increases in noise strength, the degree of departure from Gaussian noise, and the immune coefficient can accelerate the extinction of tumor cells. Numerical simulations are performed, and their results present good agreement with the theoretical results. 相似文献
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The effects of the correlation time τ between noises on the noise-enhanced stability (NES) phenomenon in an asymmetric bistable system driven by cross-correlated noise are investigated. The expressions for the average escape time from the left metastable state TL and from the right metastable state TRare derived. The results indicate that: i) The NES effect is suppressed as the correlation time τ increases for two metastable states; ii) The increase in τ speeds up the escape process from the right state for positively correlated noise, whereas its role is reverses for negatively correlated; iii) In the escape process from the left state, the role of τ is opposite to that in escape from the right state. 相似文献
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Quantifying non-classical correlations under thermal effects in a double cavity optomechanical system 下载免费PDF全文
《中国物理 B》2020,(2)
We investigate the generation of quantum correlations between mechanical modes and optical modes in an optomechanical system,using the rotating wave approximation.The system is composed of two Fabry-Perot cavities separated in space;each of the two cavities has a movable end-mirror.Our aim is the evaluation of entanglement between mechanical modes and optical modes,generated by correlations transfer from the squeezed light to the system,using Gaussian intrinsic entanglement as a witness of entanglement in continuous variables Gaussian states,and the quantification of the degree of mixedness of the Gaussian states using the purity.Then,we quantify nonclassical correlations between mechanical modes and optical modes even beyond entanglement by considering Gaussian geometric discord via the Hellinger distance.Indeed,entanglement,mixdness,and quantum discord are analyzed as a function of the parameters characterizing the system(thermal bath temperature,squeezing parameter,and optomechanical cooperativity).We find that,under thermal effect,when entanglement vanishes,purity and quantum discord remain nonzero.Remarkably,the Gaussian Hellinger discord is more robust than entanglement.The effects of the other parameters are discussed in detail. 相似文献
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研究了乘性非高斯噪声和加性高斯白噪声共同激励下非对称双稳系统的平均首次穿越时间和随机共振问题. 利用路径积分法和两态模型理论,推导出平均首次穿越时间和信噪比的表达式. 研究结果表明:势阱非对称性对两个不同方向的平均首次穿越时间的影响是不同的. 信噪比是加性噪声强度和势阱非对称性的非单调函数,系统出现了随机共振现象;信噪比是乘性噪声强度的单调函数,没有共振峰出现. 这说明该系统中乘性噪声强度和加性噪声强度对信噪比的影响是不同的.
关键词:
非高斯噪声
非对称双稳系统
平均首次穿越时间
随机共振 相似文献