论文标题
在量子病毒扩张中共同相互作用的费米的散装粘度
Bulk viscosity of resonantly interacting fermions in the quantum virial expansion
论文作者
论文摘要
我们考虑在两个和三个维度上具有零范围相互作用的两个组分费用，并计算高温状态中任意散射长度的散装粘度。我们使用有关逃生性的扩展来评估库拜公式的大块粘度，该散发性在高温下充当小参数。在Kubo公式的零频率极限中，出现了捏合奇异性，从而将逃逸的顺序降低了一个。这些奇异性可以在非零频率下将高阶顶点校正变成零频率的领先顺序，因此必须重新定位所有此类贡献。我们通过考虑这些紧缩的奇异性来提出一个精确的微观计算，以实现高温方案中的块状粘度。对于负散射长度，我们在延期中以二阶的二阶得出完整的散装粘度，并表明恢复顶点校正的自搭配方程与线性化的动力学方程相同。对于正散射长度，出现了一种新型的捏合奇异性。我们表明，绑定对的捏合奇异性会导致对散装粘度的一阶贡献，这比负散射长度低一个阶，并且顶点校正还提供了一阶贡献。我们为绑定对提出了一个新的动力学方程，该方程是从自洽的方程式衍生而来的，以恢复顶点校正。
We consider two-component fermions with a zero-range interaction both in two and three dimensions and calculate the bulk viscosity for an arbitrary scattering length in the high-temperature regime. We evaluate the Kubo formula for the bulk viscosity using an expansion with respect to the fugacity, which acts as a small parameter at high temperatures. In the zero-frequency limit of the Kubo formula, pinch singularities emerge that reduce the order of the fugacity by one. These singularities can turn higher-order vertex corrections at nonzero frequencies into the leading order at zero frequency, so that all such contributions have to be resummed. We present an exact microscopic computation for the bulk viscosity in the high-temperature regime by taking into account these pinch singularities. For negative scattering lengths, we derive the complete bulk viscosity at second order in fugacity and show that a self-consistent equation to resum the vertex corrections is identical to a linearized kinetic equation. For positive scattering lengths, a new type of pinch singularity arises for bound pairs. We show that the pinch singularity for bound pairs leads to a first-order contribution to the bulk viscosity, which is one order lower than that for negative scattering lengths, and that the vertex corrections also provide first-order contributions. We propose a new kinetic equation for bound pairs that derives from a self-consistent equation to resum the vertex corrections.
