Superdiffusive finite-temperature transport has been recently observed in a variety of integrable systems with non-Abelian global symmetries. Superdiffusion is caused by giant Goldstone-like quasiparticles stabilized by integrability. Here, we argue that these giant quasiparticles remain long-lived and give divergent contributions to the low-frequency conductivity $\sigma (\omega )$, even in systems that are not perfectly integrable. We find, perturbatively, that $\sigma (\omega )\sim {\omega }^{-1/3}$ for translation-invariant static perturbations that conserve energy and $\sigma (\omega )\sim |\log \omega |$ for noisy perturbations. The (presumable) crossover to regular diffusion appears to lie beyond low-order perturbation theory. By contrast, integrability-breaking perturbations that break the non-Abelian symmetry yield conventional diffusion. Numerical evidence supports the distinction between these two classes of perturbations.

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近可积自旋链中超扩散的稳定性

最近在具有非阿贝尔全局对称性的各种可积系统中观察到超扩散有限温度输运。超扩散是由可积性稳定的巨型 Goldstone 类准粒子引起的。在这里，我们认为这些巨大的准粒子寿命很长，并对低频电导率做出了不同的贡献。$\sigma (\omega )$，即使在不完全可集成的系统中。我们发现，扰动，$\sigma (\omega )～{\omega }^{-1/3}$ 用于保持能量和的平移不变静态扰动 $\sigma (\omega )～|\mathrm{日志}\omega |$对于嘈杂的扰动。到规则扩散的（可能的）交叉似乎超出了低阶微扰理论。相比之下，破坏非阿贝尔对称性的可积性破坏扰动会产生常规扩散。数值证据支持区分这两类扰动。