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Physica
North-Holland
Physica

North-Holland

0378-4371

Physica/Journal Physica
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    Recognition of the scale-free interval for calculating the correlation dimension using machine learning from chaotic time series

    Zhou, ShuangWang, XingyuanZhang, ChuanZhou, Wenjie...
    11页
    查看更多>>摘要：Identifying the scale-free interval is an important step in calculating the correlation dimension. In this paper, we propose a method using machine learning known as density peak based clustering algorithm to recognize the scale-free interval. First, the GP algorithm is used for computing the correlation integral index. Then, the density peak based clustering algorithm is used for classifying the second-order derivative data sets of the correlation integral curve, the zero-fluctuation data are selected to be retained, and then the gross errors are excluded from the selected data. Finally, the coefficient of determination is used to identify the scale-free interval. Some examples are provided to verify the proposed method effective. The calculated results show that our method is feasible. In addition, this research proposes a new method to identify the scale-free interval for fractional dimension calculation theory. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Entropy scaling laws in self propelled glass formers

    Sachin, C. N.Joy, Ashwin
    7页
    查看更多>>摘要：Predicting transport from equilibrium structure is a challenging problem in liquid state physics. Here we probe a glass forming liquid composed of self-propelled "active"particles and show that increasing the duration of self-propulsion makes the pair excess entropy negatively larger. The associated reduction in the number of accessible configurations per particle leads to a reduction in self-diffusivity. At moderate supercooling, the self-diffusivity is Arrhenius and in a reduced form obeys a Dzugutov like scaling law, directly yielding us a pair excess entropy that is inversely proportional to the effective temperature. In the strongly super-cooled regime, Dzugutov law does not apply and we observe that, the pair excess entropy shows a non-Arrhenius (power law) dependence on the effective temperature with an exponent that depends on the self propulsion time of the active particles. To demonstrate the generality of our scaling laws in moderately high temperatures, we set the particle interactions to be purely repulsive in one case and Lennard-Jones in the other, and find that in both the cases, the reported high temperature scaling laws are robust over variations in the duration of self propulsion. Our results may apply to transport in active colloidal suspensions, passive tracers in bacterial baths, and self-propelled granular media, to mention a few. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Entropy changes in crystalline material under phase transition and symmetry breaking

    Sinha, DhirajBouffanais, Roland
    11页
    查看更多>>摘要：Heat removal from a crystalline material at its critical temperature results in phase transitions which are associated with spontaneous symmetry breaking whereby the final state exhibits infinite degenerate states. Calculations of entropy changes in such systems are not addressed in classical thermodynamics as the system is driven away from equilibrium due to the asymmetric energy landscape of the system. Here, we present a novel mathematical formulation that allows us to calculate entropy changes in such systems while arguing that heat applied to such a system results in an increase in entropy along with the excitation of Goldstone modes. These ideas offer a novel theoretical framework towards understanding the phenomenon of entropy changes in systems driven away from equilibrium. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    A continuum model considering the uncertain velocity of preceding vehicles on gradient highways

    Zhai, CongWu, Weitiao
    16页
    查看更多>>摘要：Gradient roads are not uncommon in mountainous areas and freeways. The driving field of vision will be limited under such a complex road environment, which hinders the drivers from accurately perceiving the speed of the preceding vehicle. Accurate modeling of traffic flow in such an environment is therefore paramount to make accurate predictions and to effectively control the system. To this end, we present a modified continuum model accounting for the uncertain velocity of preceding vehicles on gradient highways. We derive the stability criterion and the KdV-Burgers equation of the proposed model via linear and nonlinear stability analysis. The density wave solution obtained by solving the above KdV-Burgers equation can explain the propagation mechanism of traffic jams near the stability curve. Numerical examples reveal that the slope information and uncertainty term exert great influence on traffic jams and energy consumption. Specifically, the effect of the slope information is positive, whereas the effect of the uncertainty term is negative. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    DNA migration through semi-circular gradient channel

    Mohanta, Dibyajyoti
    8页
    查看更多>>摘要：We study quasi-equilibrium migration of double stranded DNA (dsDNA) through semicircular narrow channel by exact enumeration method. We employ Fokker-Planck formalism to analyze the slow migration process of dsDNA through this symmetric channel which resembles the Herpes Simplex Virus-1 (HSV-1) migration through the vestibular nuclei in brainstem. We explore all possibilities of varying solvent gradient inside the semi circular area to ensure slow migration which is essential in DNA nanopore sequencing techniques. We also shed light on configurational and orientational properties of DNA and sequential preference of the dsDNA while migrating through the channel. We report that GC rich homo-sequence DNA migrates more slowly through the channel than AT rich and AT-GC di-block DNA. In this paper, a simple lattice model is developed to explore various physical parameters dependence on slow migration process of a dsDNA. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Pinning synchronization of complex networks with time-varying outer coupling and nonlinear multiple time-varying delay coupling

    Lin, HaiWang, Jingcheng
    16页
    查看更多>>摘要：This article studies the pinning control problem for complex networks with time-varying outer coupling and nonlinear multiple time-varying delay coupling. The design aim is to provide appropriate pinning feedback controllers such that the nodes converge to the consistent state as well as the equilibrium point, periodic orbit or chaotic orbit of the nonlinear part of the node dynamic. Based on Lyapunov function theory, appropriate positive-definite functions are constructed, and sufficient synchronization criteria for two kinds of complex networks with different time-varying delay coupling are obtained respectively. Meanwhile, the boundary of the time-varying outer coupling and its influence on the synchronization are investigated. The theoretical results are extended to complex networks with general time-varying delay coupling. Simulation results on complex networks consisting of six nonidentical Chua's circuits with time-varying outer coupling and nonlinear multiple time-varying delay coupling are presented to demonstrate the effectiveness of the proposed approaches. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Research on swarm consistent performance of improved Vicsek model with neighbors' degree

    Lu, XinbiaoZhang, ChiHuang, ChenQin, Buzhi...
    8页
    查看更多>>摘要：In the classical Vicsek model, it was found that the emergence of self-ordered motion in systems of particles when the direction of each particles' motion of at the next moment is updated according to its all neighbors' mean direction. However, the rapid increase of the number of particles and the complexity of particles' interaction will lead to this progress's time become too long. Therefore, in order to reduce the time from disorder to order, a novel strategy is proposed to make the directions of all particles' motions reach consensus more quickly. In this rule, we introduce the value of neighbors' degree according to the degree value, and select only part of the neighbor particles with larger degree. When the initial particles of swarm are connected, simulation results show that the emergence of consistent direction earlier in the improved Vicsek model than that in classical Vicsek model. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Cellular Automata for excitable media on a Complex Network: The effect of network disorder in the collective dynamics

    Reyes, LeonardoLaroze, David
    8页
    查看更多>>摘要：Complex adaptive systems can be modelled with Networks and Cellular Automata (CA). In the present work, we study the Greenberg-Hastings (GH) cellular automata running in the Watts-Strogatz (WS) network model. We are interested in finding the conditions under which the system operates near a critical point. We introduce the notion of leverage point in such a simple kind of model: a point in parameter space, at criticality, such that we can change the collective state of the system with a minimal effort. Within our proposed framework, the system's response to changes in disorder is maximal at the leverage point. The GH CA includes a transmission coefficient r that sets the threshold size in the dynamics. We evaluate numerically the critical transmission coefficient rc as a function of the average coordination number of the network K and of the rewiring probability p, where p controls the fluctuations in the coordination number. There is an interval of values in the transmission coefficient r for which the collective state of the system depends on network disorder. This interval narrows as the average coordination number increases and only within it we can tune for criticality by changing disorder alone. Our results are relevant for systems that operate at criticality in order to increase their dynamic range or to operate under optimal information-processing conditions. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Study of invariance of nonextensive statistics under the uniform energy spectrum translation

    Parvan, A. S.
    12页
    查看更多>>摘要：The general formalisms of the q-dual statistics, the Boltzmann-Gibbs statistics, and three versions of the Tsallis statistics known as Tsallis-1, Tsallis-2, and Tsallis-3 statistics have been considered in the canonical ensemble. We have rigorously proved that the probability distribution of the Tsallis-1 statistics is invariant under the uniform energy spectrum translation at a fixed temperature. This invariance demonstrates that the formalism of the Tsallis-1 statistics is consistent with the fundamentals of the equilibrium statistical mechanics. The same results we have obtained for the probability distributions of the Tsallis-3 statistics, Boltzmann-Gibbs statistics, and q-dual statistics. However, we have found that the probability distribution of the Tsallis-2 statistics, the expectation values of which are not consistent with the normalization condition of probabilities, is indeed not invariant under the overall shift in energy as expected. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier

    Quantum simultaneous measurement of non-commuting observables based on K-means clustering

    Cui, WeiYang, Yang
    8页
    查看更多>>摘要：Simultaneous measurement of non-commuting observables deepens the understanding of Heisenberg's uncertainty principle and has significant applications to quantum feedback control theory. Here we use techniques from machine learning to define a measure for the degree of non-commuting behavior of quantum measurements coming from the initial and final states of the measurements. Both the measurement strength effect and the angle effect between two observables have been constructed by using the K-means clustering method to reflect the defined non-commutativity measure. The rationality of the measure is demonstrated and its application in obtaining the measurement limitation that physically realizable is presented. Our work helps to advance the understanding of quantum non-commuting measurement and quantum control theory. (C) 2021 Elsevier B.V. All rights reserved.
      原文链接:
    • NSTL
    • Elsevier