In this report we review recent progress achieved in the understanding of heavy quarkonium under extreme conditions from a theory perspective. Its focus lies both on quarkonium properties in thermal equilibrium, as well as recent developments towards a genuine real-time description, valid also out-of-equilibrium. We will give an overview of the theory tools developed and deployed over the last decade, including effective field theories, lattice field theory simulations, modern methods for spectral reconstructions and the the open-quantum systems paradigm. The report will discuss in detail the concept of quarkonium melting, providing the reader with a contemporary perspective. In order to judge where future progress is needed we will also discuss recent results from experiments and phenomenological modeling of quarkonium in relativistic heavy-ion collisions.

中文翻译：

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极端条件下的重夸克

在本报告中，我们从理论的角度回顾了在极端条件下理解重夸克的最新进展。它的重点在于热平衡中的夸克性质，以及最近对真正实时描述的发展，在不平衡的情况下也有效。我们将概述过去十年中开发和部署的理论工具，包括有效场理论、晶格场理论模拟、光谱重建的现代方法和开放量子系统范式。报告将详细讨论夸克元素熔化的概念，为读者提供当代视角。