标题： 连续极限中聚合物有效理论的时间选择 显示英文标题

标题： On the choice of time in the continuum limit of polymeric effective theories

摘要： 在聚合量子理论中，一个自然的问题是所谓的连续极限，对应于“离散参数”$\lambda$趋近于零的极限。 特别是可以问这个极限是否存在，如果存在的话，极限理论是什么。 在这里，我们回顾了环量子宇宙学中一个可解模型的经典问题表述的最新结果。 我们表明，只有通过引入一个特定的$\lambda$-依赖的内部时间函数，极限$\lambda\to 0$才能被很好地定义。 然后我们将这个结果与量子理论中现有的分析进行比较，在量子理论中，动力学被表述为一个内部（$\lambda$-独立）参数，对于该参数，极限不存在。 我们简要评论了在量子理论中定义相应的时间参数所需的步骤，对于该参数，极限已被证明在经典上存在。 显示英文摘要

摘要： In polymeric quantum theories, a natural question pertains to the so called continuum limit, corresponding to the limit where the `discreteness parameter' $\lambda$ approaches zero. In particular one might ask whether the limit exists and, in that case, what the limiting theory is. Here we review recent results on the classical formulation of the problem for a soluble model in loop quantum cosmology. We show that it is only through the introduction of a particular $\lambda$-dependent internal time function that the limit $\lambda\to 0$ can be well defined. We then compare this result with the existing analysis in the quantum theory, where the dynamics was cast in terms of an internal ($\lambda$-independent) parameter for which the limit does not exist. We briefly comment on the steps needed to define the corresponding time parameter in the quantum theory for which the limit was shown to exist classically.