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arXiv 0910.0645hep-thcond-mat.str-el
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极端黑洞的零温输运系数

Transport Coefficients at Zero Temperature from Extremal Black Holes

Mohammad Edalati, Juan I. Jottar, Robert G. Leigh

摘要:

利用AdS/CFT对应研究了{ \it zero}温度和有限电荷密度下强耦合(2 + 1)维场论的输运系数.所考虑的场论与体中的极端Reissner-Nordstrom AdS_4黑洞是对偶的。我们发现,像在\cite{Faulkner:2009wj}中研究的标量和旋量算子的情况下,电荷(矢量)电流和能量动量(张量)算子的标量在低频下表现出标度行为。这种低频行为的存在与极端黑洞背景的近视界几何具有AdS_2因子有关。我们仔细地计算了剪切粘度(在零温度下),并表明剪切粘度与熵密度之比取1/4π的值。由于AdS_2因子的存在,我们认为这个结果对于与极值Reissner-Nordstrom AdS_{d+1}黑洞对偶的所有d维边界场论都是一样的.此外,我们还计算了零温度下的电荷电导率。小频率的电导率的限制行为也归因于近地平线的AdS_2因子,并认为持有的零温度边界场论的尺寸无关。最后,以极端双子AdS_4黑洞为背景,在恒定磁场的作用下,提取了电导率。

英文摘要:

Using the AdS/CFT correspondence we study transport coefficients of a strongly-coupled (2 +1)-dimensional field theory at {\it zero} temperature and finite charge density. The field theory under consideration is dual to the extremal Reissner-Nordstrom AdS_4 black hole in the bulk. We show that, like the cases of scalar and spinor operators studied in \cite{Faulkner:2009wj}, the correlators of charge (vector) current and energy-momentum (tensor) operators exhibit scaling behavior at low frequency. The existence of such low frequency behavior is related to the fact that the near-horizon geometry of the extremal black hole background has an AdS_2 factor. We carefully calculate the shear viscosity (at zero temperature) and show that the ratio of the shear viscosity to the entropy density takes the value of 1/4π. Because of the AdS_2 factor, we argue that this result stays the same for all d-dimensional boundary field theories dual to the extremal Reissner-Nordstrom AdS_{d+1} black holes. Also, we compute the charge conductivity at zero temperature. The limiting behavior of the conductivity for small frequencies is also attributed to the near horizon AdS_2 factor and is argued to hold regardless of the dimension of the zero-temperature boundary field theory. Finally, using the extremal dyonic AdS_4 black hole as the background, we extract the conductivity in the presence of a constant magnetic field.

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