标题： 重新审视棘轮原理：隐藏对称性如何阻止稳定电流 显示英文标题

标题： Revisiting the Ratchet Principle: When Hidden Symmetries Prevent Steady Currents

摘要： “棘轮原理”指出，违反宇称对称性的非平衡系统通常表现出稳态电流，这是热平衡以外的少数普遍结果之一。 我们研究了在具有空间变化波动源的主动和被动系统中观察到的该原理的例外情况。 对于稀疏系统，我们表明隐藏的时间反演对称性会阻止棘轮电流的出现。 在较高密度下，成对的作用力会破坏这种对称性，但动量场的涌现守恒定律可能仍然阻止稳态电流。 我们展示了如何通过分析方法测试该守恒律的存在，并在没有该守恒律的情况下描述棘轮电流的出现。 我们的结果表明，棘轮原理应进行修正，以排除宇称对称性、时间反演对称性和整体动量守恒。 显示英文摘要

摘要： The ``ratchet principle", which states that non-equilibrium systems violating parity symmetry generically exhibit steady-state currents, is one of the few generic results outside thermal equilibrium. We study exceptions to this principle observed in active and passive systems with spatially varying fluctuations sources. For dilute systems, we show that a hidden time-reversal symmetry prevents the emergence of ratchet currents. At higher densities, pairwise forces break this symmetry but an emergent conservation law for the momentum field may nevertheless prevent steady currents. We show how the presence of this conservation law can be tested analytically and characterize the onset of ratchet currents in its absence. Our results show that the ratchet principle should be amended to preclude parity symmetry, time-reversal symmetry, and bulk momentum conservation.