Dimensional reduction in the sky
Dimensional reduction in the sky
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天空降维
DOI：
10.1103/physrevd.87.123532
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发表时间：
2013
影响因子：
5
通讯作者：
Amelino-Camelia G
中科院分区：
文献类型：
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作者：
Amelino-Camelia G
我们探讨了在量子引力的几种方法中发现的一种机制的宇宙学意义，时空的光谱维度从红外（IR）的标准值4到紫外（UV）的较小值。具体来说，我们调用的图片中的现象与修改后的色散关系。在最小的假设下，我们发现，导致2个光谱维度的UV行为导致真空标量和张量涨落的精确标度不变的光谱，而不管状态方程。涨落的产生机制类似于已知的改变声速/光速的模型，与暴胀不同的是，光谱在离开视界之前已经是标度不变的，在冻结之后仍然如此。根据普朗克最近的结果，我们还讨论了打破精确标度不变性的情况，例如谱维下降到略高于2的值的可能性，或者下降到2但具有极慢的瞬态。我们进一步表明，张量标量比是固定的UV之间的重力和光速的速度的比率。我们的模型不仅不需要暴胀，而且在最低限度上似乎与暴胀不相容。相反，我们发现运行谱维数可以改善循环/爆炸场景的前景，解决其最简单和最吸引人的实现中存在的主要问题。
We explore the cosmological implications of a mechanism found in several approaches to quantum gravity, whereby the spectral dimension of spacetime runs from the standard value of 4 in the infrared (IR) to a smaller value in the ultraviolet (UV). Specifically, we invoke the picture where the phenomenon is associated with modified dispersion relations. With minimal assumptions, we find that UV behavior leading to 2 spectral dimensions results in an exactly scale-invariant spectrum of vacuum scalar and tensor fluctuations, regardless of the equation of state. The fluctuation production mechanism is analogous to the one known for varying speed of sound/light models and, unlike in inflation, the spectrum is already scale invariant before leaving the horizon, remaining so after freeze-in. In the light of Planck’s recent results we also discuss scenarios that break exact scale invariance, such as the possibility that the spectral dimension runs down to a value slightly higher than 2, or runs down to 2 but with an extremely slow transient. We further show that the tensor to scalar ratio is fixed by the UV ratio between the speed of gravity and the speed of light. Not only does our model not require inflation, but at its most minimal it seems incompatible with it. In contrast, we find that running spectral dimensions can improve the outlook of the cyclic/ekpyrotic scenario, solving the main problems present in its simplest and most appealing realizations.
DOI：
--
发表时间：
2006
期刊：
--
影响因子：
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作者：
Iroon Polytechniou-
通讯作者：
Iroon Polytechniou-