论文标题
通货膨胀会挤压宇宙扰动吗?
Does inflation squeeze cosmological perturbations?
论文作者
论文摘要
关于通货膨胀挤压宇宙学扰动的量子状态和纠缠与波数$ \ vec k $和$ - \ vec k $的量子状态,似乎达成共识。矛盾的是,该结果已被用来证明经典性以及通货膨胀结束时原始扰动的量子性。我们重新审查了这个问题,并指出了对模式的两种模式挤压的定义$ \ vec k $和$ - \ \ vec k $以前的工作中使用的选择仅基于选择,这些选择仅适用于与时间无关的汉密尔顿人和有限的自由度的系统。我们认为,对于传播通用时间依赖性的弗里德曼 - 罗马·罗伯逊 - 罗伯逊步行者背景的量子场,挤压状态的概念受到了歧义的影响,这与粒子定义的歧义息息相关。换句话说,我们认为“宇宙扩展是否会挤压和纠缠vavenumbers $ \ vec k $和$ - \ vec k $?”包含与“宇宙膨胀会产生颗粒?”相同的歧义。当存在其他对称性时,就像通货膨胀模型中使用的(准)de Sitter一样的空间时,就可以解决歧义,我们发现标题中问题的答案证明是负面的。我们进一步认为,这一事实并不能使宇宙学的扰动状态降低量子,至少在忽略了高斯偏离时。
There seems to exist agreement about the fact that inflation squeezes the quantum state of cosmological perturbations and entangles modes with wavenumbers $\vec k$ and $-\vec k$. Paradoxically, this result has been used to justify both the classicality as well as the quantumness of the primordial perturbations at the end of inflation. We reexamine this question and point out that the definition of two-mode squeezing of the modes $\vec k$ and $-\vec k$ used in previous work rests on choices that are only justified for systems with time-independent Hamiltonians and finitely many degrees of freedom. We argue that for quantum fields propagating on generic time-dependent Friedmann-Lemaître-Robertson-Walker backgrounds, the notion of squeezed states is subject to ambiguities, which go hand in hand with the ambiguity in the definition of particles. In other words, we argue that the question "does the cosmic expansion squeeze and entangle modes with wavenumbers $\vec k$ and $-\vec k$?" contains the same ambiguity as the question "does the cosmic expansion create particles?". When additional symmetries are present, like in the (quasi) de Sitter-like spacetimes used in inflationary models, one can resolve the ambiguities, and we find that the answer to the question in the title turns out to be in the negative. We further argue that this fact does not make the state of cosmological perturbations any less quantum, at least when deviations from Gaussianity can be neglected.