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arXiv 1605.09752cond-mat.quant-gasgr-qc
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原子玻色气体跨音速流中的声子谱和关联

Phonon spectrum and correlations in a transonic flow of an atomic Bose gas

Florent Michel, Jean-François Coupechoux, Renaud Parentani

摘要:

受J.~最近的一个实验的启发,Steinhauer,我们重新考虑了稳态跨音速流中自发辐射声子的谱和关联。后者描述的“瀑布”的配置,形成一个稳定的流的单参数家庭。对于接近其实验值的参数,尽管在声波视界附近的高梯度,频谱是准确的普朗克在相关的频域中,其中的温度从相对论的预测相差小于$10 \%$。然后,我们研究了整个视界的密度相关性和最终状态的不可分离性。我们表明,相对论表达式提供准确的近似时,初始温度不太高。我们还表明,相位的散射系数引入了有限的移位的相关性,这是迄今为止被忽视的位置。这种变化是由于流的不对称性跨越地平线,并持续在分散的制度。最后,我们将展示如何形成的声波地平线修改本地和非本地的密度相关性。

英文摘要:

Motivated by a recent experiment of J.~Steinhauer, we reconsider the spectrum and the correlations of the phonons spontaneously emitted in stationary transonic flows. The latter are described by "waterfall" configurations which form a one-parameter family of stable flows. For parameters close to their experimental values, in spite of high gradients near the sonic horizon, the spectrum is accurately planckian in the relevant frequency domain, where the temperature differs from the relativistic prediction by less than $10 \%$. We then study the density correlations across the horizon and the non-separable character of the final state. We show that the relativistic expressions provide accurate approximations when the initial temperature is not too high. We also show that the phases of the scattering coefficients introduce a finite shift of the location of the correlations which was so far overlooked. This shift is due to the asymmetry of the flow across the horizon, and persists in the dispersion-less regime. Finally we show how the formation of the sonic horizon modifies both local and non-local density correlations.

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