Christodoulidi, H, Tsallis, C. and Bountis, T. (2014) FermiPastaUlam model with longrange interactions: Dynamics and thermostatistics. EPL (Europhysics Letters), 108 (4). p. 40006. ISSN 02955075
Full content URL: http://doi.org/10.1209/02955075/108/40006
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Item Type:  Article 

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Abstract
We study a longrange–interaction generalisation of the onedimensional FermiPastaUlam (FPU) βmodel, by introducing a quartic interaction coupling constant that decays as $1/r^\alpha\ (\alpha \ge 0)$ (with strength characterised by b > 0). In the $\alpha \to\infty$ limit we recover the original FPU model. Through molecular dynamics we show that i) for $\alpha \geq 1$ the maximal Lyapunov exponent remains finite and positive for an increasing number of oscillators N, whereas, for $0 \le \alpha <1$ , it asymptotically decreases as $N^{\kappa(\alpha)}$ ; ii) the distribution of timeaveraged velocities is Maxwellian for α large enough, whereas it is well approached by a qGaussian, with the index $q(\alpha)$ monotonically decreasing from about 1.5 to 1 (Gaussian) when α increases from zero to close to one. For α small enough, a crossover occurs at time tc from qstatistics to BoltzmannGibbs (BG) thermostatistics, which defines a "phase diagram" for the system with a linear boundary of the form $1/N \propto b^\delta /t_c^\gamma$ with $\gamma >0$ and $\delta >0$ , in such a way that the q = 1 (BG) behaviour dominates in the $\lim_{N \to\infty} \lim_{t \to\infty}$ ordering, while in the $\lim_{t \to\infty} \lim_{N \to\infty}$ ordering q > 1 statistics prevails.
Keywords:  Classical statistical mechanics, Nonlinear dynamics and chaos, Entropy 

Subjects:  G Mathematical and Computer Sciences > G150 Mathematical Modelling G Mathematical and Computer Sciences > G121 Mechanics (Mathematical) F Physical Sciences > F340 Mathematical & Theoretical Physics 
Divisions:  College of Science > School of Mathematics and Physics 
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ID Code:  37015 
Deposited On:  16 Sep 2019 10:02 
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