The perturbations in the early universe are generated as a result of the interplay between quantum field theory and gravitation. Since these primordial perturbations lead to the anisotropies in the cosmic microwave background and eventually to the inhomogeneities in the Large Scale Structure (LSS), they provide a unique opportunity to probe issues which are fundamental to our understanding of quantum physics and gravitation. One such fundamental issue that remains to be satisfactorily addressed is the transition of the primordial perturbations from their quantum origins to the LSS which can be characterized completely in terms of classical quantities. Classical bouncing universes provide an alternative to the more conventional inflationary paradigm as they can help overcome the horizon problem in a fashion very similar to inflation. While the problem of the quantum-to-classical transition of the primordial perturbations has been investigated extensively in the context of inflation, we find that there has been a rather limited effort toward studying the issue in classical bouncing universes. In this work, we analyze certain aspects of this problem with the example of tensor perturbations produced in classical matter and near-matter bouncing universes. We investigate the issue mainly from two perspectives. First, we approach the problem by examining the extent of squeezing of a quantum state associated with the tensor perturbations with the help of the Wigner function. Second, we analyze the issue from the perspective of the quantum measurement problem. In particular, we study the effects of wave function collapse, using a phenomenological model known as continuous spontaneous localization, on the tensor power spectra. We conclude with a discussion of results.

中文翻译：

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经典弹跳宇宙中量子到经典的转变和连续自发定位的印记

早期宇宙中的扰动是量子场论和引力相互作用的结果。由于这些原始扰动导致宇宙微波背景中的各向异性，并最终导致大尺度结构 (LSS) 中的不均匀性，它们提供了一个独特的机会来探索对我们理解量子物理学和引力至关重要的问题。有待令人满意地解决的一个这样的基本问题是原始扰动从它们的量子起源到可以完全用经典量来表征的 LSS 的转变。经典的弹跳宇宙为更传统的暴胀范式提供了一种替代方案，因为它们可以帮助以非常类似于暴胀的方式克服视界问题。虽然原始扰动的量子到经典转变的问题已经在暴胀的背景下进行了广泛的研究，但我们发现在经典的弹跳宇宙中研究这个问题的努力相当有限。在这项工作中，我们以经典物质和近物质弹跳宇宙中产生的张量扰动为例分析了这个问题的某些方面。我们主要从两个方面来研究这个问题。首先，我们通过在 Wigner 函数的帮助下检查与张量扰动相关的量子态的压缩程度来解决这个问题。其次，我们从量子测量问题的角度来分析这个问题。特别是，我们研究了波函数坍缩的影响，在张量功率谱上使用称为连续自发定位的现象学模型。我们以对结果的讨论结束。