In common fluids, viscosity is associated with dissipation. However, when time-reversal symmetry is broken a new type of nondissipative “viscosity” emerges. Recent theories and experiments on classical 2D systems with active spinning particles have heightened interest in “odd viscosity,” but a microscopic theory for it in active materials is still absent. Here, we present such first-principles microscopic Hamiltonian theory, valid for both 2D and 3D, showing that odd viscosity is present in any system, even at zero temperature, with globally or locally aligned spinning components. Our work substantially extends the applicability of odd viscosity into 3D fluids, and specifically to internally driven active materials, such as living matter (e.g., actomyosin gels). We find intriguing 3D effects of odd viscosity such as propagation of anisotropic bulk shear waves and breakdown of Bernoulli’s principle.

中文翻译：

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活性物质中的奇粘度：微观起源和 3D 效果

在普通流体中，粘度与耗散有关。然而，当时间反转对称性被打破时，就会出现一种新型的非耗散“粘度”。最近关于具有活性自旋粒子的经典 2D 系统的理论和实验引起了人们对“奇数粘度”的兴趣，但在活性材料中仍然没有关于它的微观理论。在这里，我们提出了这样的第一性原理微观哈密顿理论，对 2D 和 3D 都有效，表明在任何系统中都存在奇怪的粘度，即使在零温度下，具有全局或局部对齐的纺丝组件。我们的工作大大扩展了奇数粘度在 3D 流体中的适用性，特别是对内部驱动的活性材料，如生物物质（例如，肌动球蛋白凝胶）的适用性。