标题： 封闭宇宙中的量子力学和引力观察者 显示英文标题

标题： Quantum mechanics and observers for gravity in a closed universe

摘要： 近期基于量子极值面公式或引力路径积分的论据已经给出了相当有说服力的证据，表明封闭宇宙中的引力量子理论的希尔伯特空间是一维且实数的。 这如何与我们自身经验的复杂性相一致呢？ 本文提出，在封闭宇宙中的任何观察者 $Ob$ 的体验可以近似地由一个具有希尔伯特空间的量子力学理论描述，该希尔伯特空间的维度大约为 $e^{S_{Ob}}$，其中 $S_{Ob}$ 是 $Ob$ 的自由度数量。 此外，我们论证了这种描述中的误差在 $S_{Ob}$ 中是指数级小的。 我们利用引力路径积分和全息编码解释提供了这一提议的证据，并解释了在适当情况下，类似效应如何出现在黑洞物理中。 显示英文摘要

摘要： Recent arguments based on the quantum extremal surface formula or the gravitational path integral have given fairly compelling evidence that the Hilbert space of quantum gravity in a closed universe is one-dimensional and real. How can this be consistent with the complexity of our own experiences? In this paper we propose that the experiences of any observer $Ob$ in a closed universe can be approximately described by a quantum mechanical theory with a Hilbert space whose dimension is roughly $e^{S_{Ob}}$, where $S_{Ob}$ is the number of degrees of freedom of $Ob$. Moreover we argue that the errors in this description are exponentially small in $S_{Ob}$. We give evidence for this proposal using the gravitational path integral and the coding interpretation of holography, and we explain how similar effects arise in black hole physics in appropriate circumstances.