共查询到20条相似文献,搜索用时 46 毫秒
1.
提出了一种基于时空混沌系统的Hash函数构造方法.以线性变换后的消息数作为一组初值来驱动单向耦合映像格子的时空混沌系统,产生时空混沌序列,取其空间最后一组混沌序列的适当项,线性映射为Hash值要求的128bit值.研究结果表明,这种基于时空混沌系统的Hash函数具有很好的单向性、弱碰撞性、初值敏感性,较基于低维混沌映射的Hash函数具有更强的保密性能,且实现简单.
关键词:
时空混沌
Hash函数
单向耦合映像格子 相似文献
2.
F. Krzakala O.C. Martin 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):199-208
We address the problem of chaotic temperature dependence in disordered glassy systems at equilibrium by following states of
a random-energy random-entropy model in temperature; of particular interest are the crossings of the free-energies of these
states. We find that this model exhibits strong, weak or no temperature chaos depending on the value of an exponent. This
allows us to write a general criterion for temperature chaos in disordered systems, predicting the presence of temperature
chaos in the Sherrington-Kirkpatrick and Edwards-Anderson spin glass models, albeit when the number of spins is large enough.
The absence of chaos for smaller systems may justify why it is difficult to observe chaos with current simulations. We also
illustrate our findings by studying temperature chaos in the naıve mean field equations for the Edwards-Anderson spin glass.
Received 27 March 2002 Published online 19 July 2002 相似文献
3.
We solve the initial value problem associated to the nonlinear Boltzmann equation in the case in which the initial distribution has sufficiently small spatial gradients.Supported by C.N.R.-GNFM and MPI 相似文献
4.
Juan Antonio Valiente Kroon 《Communications in Mathematical Physics》2010,298(3):673-706
Given a time symmetric initial data set for the vacuum Einstein field equations which is conformally flat, it is shown that
the solutions to the regular finite initial value problem at spatial infinity extend smoothly through the critical sets where
null infinity touches spatial infinity if and only if the initial data coincides with Schwarzschild data. 相似文献
5.
6.
Bing Tang 《中国物理C(英文版)》2021,45(5):055101-055101-10
Based on the Melnikov method, we investigate chaotic behaviors in the extended thermodynamic phase space for a slowly rotating Kerr-AdS black hole under temporal and spatial perturbations. Our results show that the temporal perturbation coming from a thermal quench of the spinodal region in the phase diagram may cause temporal chaos only when the perturbation amplitude is above a critical value, which involves the angular momentum J. Under the spatial perturbation, however, it is found that spatial chaos always occurs, independent of the perturbation amplitude. 相似文献
7.
The bifurcation threshold value of the chaos detection system for a weak signal* 总被引:6,自引:0,他引:6
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Recently, it has become an important problem to confirm the bifurcation threshold value of a chaos detectionsystem for a weak signal in the fields of chaos detection. It is directly related to whether the results of chaos detectionare correct or not. In this paper, the discrimination system for the dynamic behaviour of a chaos detection system fora weak signal is established by using the theory of linear differential equation with periodic coefficients and computingthe Lyapunov exponents of the chaos detection system; and then, the movement state of the chaos detection system isdefined. The simulation experiments show that this method can exactly confirm the bifurcation threshold value of thechaos detection svstem. 相似文献
8.
Quantum chaos is a subject whose major goal is to identify and to investigate different quantum signatures of classical chaos.
Here we study entanglement production in coupled chaotic systems as a possible quantum indicator of classical chaos. We use
coupled kicked tops as a model for our extensive numerical studies. We find that, in general, chaos in the system produces
more entanglement. However, coupling strength between two subsystems is also a very important parameter for entanglement production.
Here we show how chaos can lead to large entanglement which is universal and describable by random matrix theory (RMT). We
also explain entanglement production in coupled strongly chaotic systems by deriving a formula based on RMT. This formula
is valid for arbitrary coupling strengths, as well as for sufficiently long time. Here we investigate also the effect of chaos
on the entanglement production for the mixed initial state. We find that many properties of the mixed-state entanglement production
are qualitatively similar to the pure state entanglement production. We however still lack an analytical understanding of
the mixed-state entanglement production in chaotic systems. 相似文献
9.
Zhen-huan Teng 《Journal of computational physics》2010,229(10):3792-3801
The initial value problem of convex conservation laws, which includes the famous Burgers’ (inviscid) equation, plays an important rule not only in theoretical analysis for conservation laws, but also in numerical computations for various numerical methods. For example, the initial value problem of the Burgers’ equation is one of the most popular benchmarks in testing various numerical methods. But in all the numerical tests the initial data have to be assumed that they are either periodic or having a compact support, so that periodic boundary conditions at the periodic boundaries or two constant boundary conditions at two far apart spatial artificial boundaries can be used in practical computations. In this paper for the initial value problem with any initial data we propose exact boundary conditions at two spatial artificial boundaries, which contain a finite computational domain, by using the Lax’s exact formulas for the convex conservation laws. The well-posedness of the initial-boundary problem is discussed and the finite difference schemes applied to the artificial boundary problems are described. Numerical tests with the proposed artificial boundary conditions are carried out by using the Lax–Friedrichs monotone difference schemes. 相似文献
10.
结合DC-DC变换器非线性特性随反馈增益k变化的关系,以及熵能够反映序列总体统计特征的特点,提出一种基于熵估计DC-DC变换器非线性行为的新方法. 以一阶电压反馈不连续导电模式 DCM Buck和Boost变换器为例,详细分析了不同反馈增益k和初值x0形成的数值序列及熵的分布情况. 研究结果表明:DC-DC变换器的熵由反馈增益k决定,与初值x0无关,最终小于理论极大值log2N (N为统计区间个数);熵能够准确区分DC-DC变换器的倍周期分岔和混沌行为,从而得到一种新的可量化的DC-DC变换器非线性动力学行为指标;完善了该类变换器非线性动力学分析的理论和方法.
关键词:
DC-DC变换器
熵
混沌
k')" href="#">反馈增益k 相似文献
11.
We propose a cryptographic scheme based
on spatiotemporal chaos of
coupled map lattices (CML) ,which is based on one-time pad. The
structure of the cryptosystem determines that the progress in
decryption implies the progress in exploring the dynamical behavior
of spatiotemporal chaos in CML. A part of the initial condition of
CML is used as a secret key, and the recovery of the secret key by
exhaustive search is impossible due to the sensitivity to the
initial condition in spatiotemporal chaos system. Specially the
software implementation of the scheme is easy. 相似文献
12.
We study directed transport in a classical deterministic dissipative system. We consider the generic case of mixed phase space and show that large ratchet currents can be generated thanks to the presence, in the Hamiltonian limit, of transporting stability islands embedded in the chaotic sea. Because of the simultaneous presence of chaos and dissipation the stationary value of the current is independent of initial conditions, except for initial states with very small measure. 相似文献
13.
Paul T. Allen Lars Andersson Alvaro Restuccia 《Communications in Mathematical Physics》2011,301(2):383-410
In this paper we consider the classical initial value problem for the bosonic membrane in light cone gauge. A Hamiltonian
reduction gives a system with one constraint, the area preserving constraint. The Hamiltonian evolution equations corresponding
to this system, however, fail to be hyperbolic. Making use of the area preserving constraint, an equivalent system of evolution
equations is found, which is hyperbolic and has a well-posed initial value problem. We are thus able to solve the initial
value problem for the Hamiltonian evolution equations by means of this equivalent system. We furthermore obtain a blowup criterion
for the membrane evolution equations, and show, making use of the constraint, that one may achieve improved regularity estimates. 相似文献
14.
提出了混沌神经网络的动态阈值控制方法, 将大脑脑电波的主要成分, 正弦信号作为控制变量实现对混沌神经网络内部状态的阈值动态改变, 从而达到了控制混沌神经网络混沌的目的. 利用该方法可以将混沌神经网络的输出稳定在一个与网络初始模式相关的存储模式和其反相模式上, 从而使混沌神经网络在模式识别、信息搜索等信息处理功能得以实现. 该控制方法不需要事先指定阈值, 是一种自适应方法, 符合实际人脑的思维运动.
关键词:
混沌控制
混沌神经网络
动态阈值控制
信息处理 相似文献
15.
We examine the dynamics of a wave packet that initially corresponds to a coherent state in the model of a quantum rotator
excited by a periodic sequence of kicks. This model is the main model of quantum chaos and allows for a transition from regular
behavior to chaotic in the classical limit. By doing a numerical experiment we study the generation of squeezed states in
quasiclassical conditions and in a time interval when quantum-classical correspondence is well-defined. We find that the degree
of squeezing depends on the degree of local instability in the system and increases with the Chirikov classical stochasticity
parameter. We also discuss the dependence of the degree of squeezing on the initial width of the packet, the problem of stability
and observability of squeezed states in the transition to quantum chaos, and the dynamics of disintegration of wave packets
in quantum chaos.
Zh. éksp. Teor. Fiz. 113, 111–127 (January 1998) 相似文献
16.
Sasa SI 《Chaos (Woodbury, N.Y.)》1996,6(2):238-242
We present a simple mathematical model in which a time averaged pattern emerges out of spatio-temporal chaos as a result of the collective action of chaotic fluctuations. Our evolution equation possesses spatial translational symmetry under periodic boundary conditions. Thus the spatial inhomogeneity of the statistical state arises through spontaneous symmetry breaking. The transition from a state of homogeneous spatio-temporal chaos to one exhibiting spatial order is explained by introducing a collective viscosity which relates the averaged pattern with a correlation of the fluctuations. (c) 1996 American Institute of Physics. 相似文献
17.
A quantum system which is allowed to interact with its boundary in a self-consistent way is shown to exhibit chaos. We conjecture that in general genuine wave chaos (decaying autocorrelation functions, exponential sensitivity of wavefunctions to initial wavefunction configurations) can be obtained whenever a wavefield is allowed to modify its confining boundaries in a self-consistent way. We suggest to test this conjecture in the acoustic regime. 相似文献
18.
F. T. Arecchi 《The European physical journal. Special topics》2007,146(1):205-216
A scientific problem described within a given code is mapped by a corresponding computational problem, We call complexity (algorithmic) the bit length of the shortest instruction that solves the problem. Deterministic chaos in general affects a dynamical system
making the corresponding problem experimentally and computationally heavy, since one must reset the initial conditions at
a rate higher than that of information loss (Kolmogorov entropy). One can control chaos by adding to the system new degrees
of freedom (information swapping: information lost by chaos is replaced by that arising from the new degrees of freedom). This implies a change of code, or
a new augmented model.
Within a single code, changing hypotheses means fixing different sets of control parameters, each with a different a-priori
probability, to be then confirmed and transformed into an a-posteriori probability via Bayes theorem. Sequential application
of Bayes rule is nothing else than the Darwinian strategy in evolutionary biology. The sequence is a steepest ascent algorithm,
which stops once maximum probability has been reached. At this point the hypothesis exploration stops.
By changing code (and hence the set of relevant variables) one can start again to formulate new classes of hypotheses. We
call creativity the action of code changing, which is guided by hints not formalized within the previous code, whence not accessible to a
computer. We call semantic complexity the number of different scientific codes, or models, that describe a situation. It is however a fuzzy concept, in so far as this number changes due to interaction of the operator
with the context. These considerations are illustrated with reference to a cognitive task, starting from synchronization of
neuron arrays in a perceptual area and tracing the putative path toward a model building.
Since this is a report on work in progress, we skip technicalities in order to stress the gist of the question, and provide
references to more detailed work. 相似文献
19.
D. Bennett A. R. Bishop S. E. Trullinger 《Zeitschrift für Physik B Condensed Matter》1982,47(3):265-277
Representative example of preliminary numerical results are presented for solutions of the deterministic sine-Gordon equation under the influence of damping and a sinusoidal uniform driving force. Depending on the choice of (inhomogeneous) initial conditions and values of the amplitude and frequency of the driving force, we find a great variety of possible responses, including: (i) permanent spatial structures riding on an overall background motion which can be temporally chaotic or not, (ii) intermittent transitions between at least two metastable spatial structures which are typically a localized breather-like structure and an extended wave train, in the presence of temporal chaos or not and with large- or small-amplitude background motion. For some parameter values, we find very similar power spectra for different initial conditions, while other cases show considerable dependence on initial conditions. Both the spatial and temporal behavior of the response can exhibit extreme sensitivity to small changes in the parameters. 相似文献
20.
Discretization of phase space usually nullifies chaos in dynamical systems. We show that if randomness is associated with discretization dynamical chaos may survive and be indistinguishable from that of the original chaotic system, when an entropic, coarse-grained analysis is performed. Relevance of this phenomenon to the problem of quantum chaos is discussed. 相似文献