Speckle from phase-ordering systems

被引:57
作者
Brown, G
Rikvold, PA
Sutton, M
Grant, M
机构
[1] McGill Univ, Dept Phys, Montreal, PQ H3A 2T8, Canada
[2] McGill Univ, Ctr Phys Mat, Montreal, PQ H3A 2T8, Canada
[3] Florida State Univ, Ctr Mat Res & Technol, Supercomp Computat Res Inst, Tallahassee, FL 32306 USA
[4] Florida State Univ, Dept Phys, Tallahassee, FL 32306 USA
[5] Kyoto Univ, Fac Integrated Human Studies, Dept Fundamental Sci, Kyoto 606, Japan
来源
PHYSICAL REVIEW E | 1997年 / 56卷 / 06期
基金
美国国家科学基金会;
关键词
D O I
10.1103/PhysRevE.56.6601
中图分类号
O35 [流体力学]; O53 [等离子体物理学];
学科分类号
070204 ; 080103 ; 080704 ;
摘要
The statistical properties of coherent radiation scattered from phase-ordering materials are studied in detail using large-scale computer simulations and analytic arguments. Specifically, we consider a two-dimensional model with a nonconserved, scalar order parameter (model A), quenched through an order-disorder transition into the two-phase regime. For such systems it is well established that the standard scaling hypothesis applies, consequently, the average scattering intensity at wave vector k and time tau is proportional to a scaling function which depends only on a rescaled time, t similar to \k\(2) tau. We find that the simulated intensities are exponentially distributed, and the time-dependent average is well approximated using a scaling function due to Ohta, Jasnow, and Kawasaki. Considering fluctuations around the average behavior, we find that the covariance of the scattering intensity for a single wave vector at two different times is proportional to a scaling function with natural variables delta t = \t(1) - t(2)\ and (t) over bar = (t(1) + t(2))/2. In the asymptotic large-(t) over bar limit this scaling function depends only on z = delta t/(t) over bar(1/2). For small values of z, the scaling function is quadratic, corresponding to highly persistent behavior of the intensity fluctuations. We empirically establish that the intensity covariance (for k not equal 0) equals the square of the spatial Fourier transform of the two-time, two-point correlation function of the order parameter. This connection allows sensitive testing, either experimental or numerical, of existing theories for two-time correlations in systems undergoing order-disorder phase transitions. Comparison between theoretical scaling functions and our numerical results requires no adjustable parameters.
引用
收藏
页码:6601 / 6612
页数:12
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