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arXiv 0904.1379cond-mat.stat-mechcond-mat.supr-con
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超流turbulence在低温极限下的衰变理论

Theory of decay of superfluid turbulence in the low-temperature limit

E. V. Kozik, B. V. Svistunov

摘要:

本文综述了超流湍流的弛豫动力学理论,即在很低温度下,当涡的运动是保守的时,量子化涡线的缠结。虽然衰变的某些重要方面取决于纠缠是否是非结构化的,就像Kibble-Zurek图片中的那样,或者本质上是极化的,就像模仿经典湍流的Richardson-Kolmogorov制度的那样,但它们有共同的基本特征。在这两种情况下,在波数空间中存在一个渐近范围,其中能量通量由开尔文波(Kelvons)的级联支持-沿涡丝传播的旋进扭曲。在足够大的波数,开尔文波级联是由三开尔文弹性散射支持。在T=0时,开尔文波级联的耗散截止是由于声子的发射,其中基本过程将两个动量几乎相反的开尔文子转换为一个体声子。除了标准的守恒律外,局域诱导近似(LIA)的可积性在理论中也起着至关重要的作用,LIA的可积性受参数Λ= \ln(λ/a_0)的控制,λ是特征Kelvon波长,a_0是涡核半径。虽然排除了纯三开尔文叶栅的直接开始,但由于与涡线重连相关的动力学通道的可用性,LIA的可积性不会堵塞叶栅。我们认为,从Richardson-Kolmogorov的开尔文波级联的交叉是由于最终的主导地位的局部感应的一条线的集体感应的极化涡,这会导致古典流体制度的崩溃,并产生一个重联驱动的惯性范围。

英文摘要:

We review the theory of relaxational kinetics of superfluid turbulence--a tangle of quantized vortex lines--in the limit of very low temperatures when the motion of vortices is conservative. While certain important aspects of the decay depend on whether the tangle is non-structured, like the one in the Kibble-Zurek picture, or essentially polarized, like the one that emulates the Richardson-Kolmogorov regime of classical turbulence, there are common fundamental features. In both cases, there exists an asymptotic range in the wavenumber space where the energy flux is supported by the cascade of Kelvin waves (kelvons)--precessing distortions propagating along the vortex filaments. At large enough wavenumbers, the Kelvin-wave cascade is supported by three-kelvon elastic scattering. At T=0 the dissipative cutoff of the Kelvin-wave cascade is due to the emission of phonons, in which an elementary process converts two kelvons with almost opposite momenta into one bulk phonon. Along with the standard set of conservation laws, a crucial role in the theory is played by the fact of integrability of the local induction approximation (LIA) controlled by the parameter Λ= \ln (λ/a_0), with λthe characteristic kelvon wavelength and a_0 the vortex core radius. While excluding a straightforward onset of the pure three-kelvon cascade, the integrability of LIA does not plug the cascade because of the availability of the kinetic channels associated with vortex line reconnections. We argue that the crossover from Richardson-Kolmogorov to the Kelvin-wave cascade is due to eventual dominance of local induction of a single line over the collective induction of polarized eddies, which causes the breakdown of classical-fluid regime and gives rise to a reconnection-driven inertial range.

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