[Abridged] Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability, and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability, supplemented with a survey of numerical simulations that aim to capture the non-linear evolution. We emphasize the role of thermodynamics and large scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analytic predictions and numerical results. We highlight open questions related to (1) the development of a turbulent cascade in thin disks, and (2) the role of mode-mode coupling in setting the maximum angular momentum transport rate in thick disks.

中文翻译：

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环绕恒星盘中的引力不稳定性

[已删节] 恒星和行星的形成是由原恒星盘和原行星盘介导的引力坍缩和角动量传输的复杂结果。在这篇综述中，我们关注引力不稳定性在这个过程中的作用。我们首先简要概述可能受引力不稳定性影响的大质量盘的观测证据，然后强调不稳定性在原恒星和原行星盘中表现出来的不同方式：旋臂的产生、小尺度湍流状密度波动和磁盘本身的碎片。我们提出了描述不稳定性线性增长阶段的分析理论，并辅以旨在捕捉非线性演化的数值模拟调查。我们强调热力学和大规模入射在控制不稳定性结果中的作用。尽管文献中存在明显的争议，但我们在分析预测和数值结果之间表现出惊人的一致性。我们强调了与 (1) 薄盘中湍流级联的发展，以及 (2) 模式-模式耦合在设置厚盘中最大角动量传输速率中的作用相关的开放性问题。