论文标题
WKB恢复量子宇宙学时间的方法：预测和缺点
WKB Approaches to Restore Time in Quantum Cosmology: Predictions and Shortcomings
论文作者
论文摘要
在这篇综述中，我们分析了有关将重力 - 象征系统分离到靠近准经典状态和“小”量子子集的部分的可能性。所考虑的方法都依赖于通过顺序参数的WKB扩展，而自然舞台由Bianchi Universe Minisuperspace组成。我们首先讨论如何将WKB扩展限制为近似的第一阶，可以为量子子系统恢复，按照经典的重力背景书写的schrödinger方程。我们在Bianchi IX模型的“角”配置中提供了一些量子子系统的应用，并在两个各向异性自由度中的小量子中识别量子变量。最令人惊讶的结果是，当场景随着时间的流逝向后外推时，有可能获得非单明一角的bianchi ix宇宙学。我们还提供了有关该结果扩展到通用宇宙学解决方案的一些基本提示。在审查的最后一部分中，我们将相同的方案视为仅识别物质变量制成的量子子集的下一个近似顺序。我们处理量子重力校正的非单身形态的非常基本的问题，讨论了一些拟议的重新制定。我们没有通过标签时间上的经典重力变量之一来构建时间依赖性，而是分析了最近通过固定参考框架来构建时间的建议。可以通过引入所谓的“运动动作”以及著名的Kuchar-Torre配方来达到该方案。在这两种情况下，修订的用于量子重力校正的Schrödinger方程都具有相同的形态，我们提供了模型的宇宙学实现，以阐明其可能的预测。
In this review, we analyse different aspects concerning the possibility to separate a gravity-matter system into a part which lives close to a quasi-classical state and a "small" quantum subset. The considered approaches are all relying on a WKB expansion of the dynamics by an order parameter and the natural arena consists of the Bianchi universe minisuperspace. We first discuss how, limiting the WKB expansion to the first order of approximation, it is possible to recover for the quantum subsystem a Schrödinger equation as written on the classical gravitational background. We give some applications for the quantum subsystem in the "corner" configuration of the Bianchi IX model, identifying the quantum variable in the small one of the two anisotropy degrees of freedom. The most surprising result is the possibility to get a non-singular Bianchi IX cosmology when the scenario is extrapolated backwards in time. We also provide some basic hints on the extension of this result to the generic cosmological solution. In the last part of the review, we consider the same scheme to the next order of approximation identifying the quantum subset as made of matter variables only. We deal with the very fundamental problem of non-unitary morphology of the quantum gravity corrections to quantum field theory discussing some proposed reformulations. Instead of constructing the time dependence via that one of the classical gravitational variables on the label time, we analyse a recent proposal to construct time by fixing a reference frame. This scheme can be reached both introducing the so-called "kinematical action", as well as by the well-known Kuchar-Torre formulation. In both cases, the Schrödinger equation, amended for quantum gravity corrections, has the same morphology and we provide a cosmological implementation of the model, to elucidate its possible predictions.
