Weakly interacting quasiparticles play a central role in the low-energy description of many phases of quantum matter. At higher energies, however, quasiparticles cease to be well defined in generic many-body systems owing to a proliferation of decay channels. In this review, we discuss the phenomenon of quantum many-body scars, which can give rise to certain species of stable quasiparticles throughout the energy spectrum. This goes along with a set of unusual nonequilibrium phenomena including many-body revivals and nonthermal stationary states. We provide a pedagogical exposition of this physics via a simple yet comprehensive example, that of a spin-1 XY model. We place our discussion in the broader context of symmetry-based constructions of many-body scar states, projector embeddings, and Hilbert space fragmentation. We conclude with a summary of experimental progress and theoretical puzzles.

中文翻译：

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量子多体疤痕：准粒子视角


弱相互作用的准粒子在量子物质的许多相的低能描述中起着核心作用。然而，在更高的能量下，由于衰变通道的扩散，准粒子在通用多体系统中不再被明确定义。在这篇综述中，我们讨论了量子多体疤痕的现象，它可以在整个能谱中产生某些种类的稳定准粒子。这与一系列不寻常的非平衡现象相伴而生，包括多体复兴和非热稳态。我们通过一个简单而全面的示例（即 spin-1 XY 模型）对这种物理学进行了教学阐述。我们将讨论置于基于对称性的多体疤痕状态构建、投影仪嵌入和希尔伯特空间碎片化的更广泛背景下。最后，我们总结了实验进展和理论难题。