Weakening gravity for dark matter in a type-II minimally modified gravity
Weakening gravity for dark matter in a type-II minimally modified gravity
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DOI：
10.1088/1475-7516/2021/04/018
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发表时间：
2020-11
影响因子：
6.4
通讯作者：
Antonio De Felice;S. Mukohyama
中科院分区：
文献类型：
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作者：
Antonio De Felice;S. Mukohyama
我们提出了一个新的宇宙学框架，在这个框架中，在不引入额外的引力自由度的情况下，晚时间作用在暗物质上的引力强度可以弱于标准物质场上的引力强度。该框架将暗物质整合到最近被提出作为暗能量模仿者的第二类最小修改引力中。使这样一个框架成为可能的想法包括将暗物质拉格朗日量和宇宙学常数耦合到广义相对论（GR）正则变换框架中的度量。在施加一个规范固定约束，这明确地打破了时间的非同态不变性，我们保持引力自由度的数量为2，在GR。然后，我们使逆正则变换，使理论回到原来的框架，在那里可以添加标准的物质场。这个框架包含两个自由的时间函数，它们指定了上述正则变换的生成泛函，然后用于实现哈勃膨胀率H（z）和暗物质有效引力常数Geff（z）的期望时间演化。因此，本文的目的是提供一个新的框架，以解决目前在今天的宇宙学的两个难题，即H0张力和S8张力，同时。当暗物质在这个框架中是冷的时，我们将相应的宇宙学模型称为V正则冷暗物质（VCCDM），因为标准ΛCDM中的宇宙学常数Λ被一个辅助场的函数V（λ）所取代，并且CDM在正则变换框架中与度规最小耦合。
We propose a new cosmological framework in which the strength of the gravitational force acted on dark matter at late time can be weaker than that on the standard matter fields without introducing extra gravitational degrees of freedom. The framework integrates dark matter into a type-II minimally modified gravity that was recently proposed as a dark energy mimicker. The idea that makes such a framework possible consists of coupling a dark matter Lagrangian and a cosmological constant to the metric in a canonically transformed frame of general relativity (GR). On imposing a gauge fixing constraint, which explicitly breaks the temporal diffeomorphism invariance, we keep the number of gravitational degrees of freedom to be two, as in GR. We then make the inverse canonical transformation to bring the theory back to the original frame, where one can add the standard matter fields. This framework contains two free functions of time which specify the generating functional of the above mentioned canonical transformation and which are then used in order to realize desired time evolutions of both the Hubble expansion rate H(z) and the effective gravitational constant for dark matter Geff(z). The aim of this paper is therefore to provide a new framework to address the two puzzles present in today's cosmology, i.e. the H0 tension and the S8 tension, simultaneously. When the dark matter is cold in this framework, we dub the corresponding cosmological model the V Canonical Cold Dark Matter (VCCDM), as the cosmological constant Λ in the standard ΛCDM is replaced by a function V(ϕ) of an auxiliary field ϕ and the CDM is minimally coupled to the metric in a canonically transformed frame.