论文标题
II型最小重力的理论
A theory of type-II minimally modified gravity
论文作者
论文摘要
我们提出了一种修改的重力理论，该理论仅传播两个局部引力的自由度，并且没有爱因斯坦框架。根据JCAP 01（2019）017 [ARXIV：1810.01047 [GR-QC]]的分类，这是II型最小化重力理论。该理论的特征在于重力常数$ g _ {\ rm n} $和非动态辅助场$ ϕ $的函数$ v（ϕ）$，该$ ϕ $ n扮演了深色能量的作用。一旦修复了同质和各向同性宇宙学背景，确定$ v（ϕ）$的形式，该理论不再具有免费参数或免费功能，除了$ g _ {\ rm n} $。对于$ v'（ϕ）= 0 $，理论将$ g_n $作为牛顿的常数和$ v = const。$是宇宙常数。对于$ v'（ϕ）\ ne 0 $，这表明重力的行为与GR的行为不同，但是$ g _ {\ rm n} $的GR是Newton的常数，因为牛顿的常数在距离和时间尺度上的弱重力均与与$ v（ϕ）$相关的比例相关的较短。因此，该理论提供了最简单的宇宙学框架，其中可以通过观察数据来测试与GR的偏差。
We propose a modified gravity theory that propagates only two local gravitational degrees of freedom and that does not have an Einstein frame. According to the classification in JCAP 01 (2019) 017 [arXiv:1810.01047 [gr-qc]], this is a type-II minimally modified gravity theory. The theory is characterized by the gravitational constant $G_{\rm N}$ and a function $V(ϕ)$ of a non-dynamical auxiliary field $ϕ$ that plays the role of dark energy. Once one fixes a homogeneous and isotropic cosmological background, the form of $V(ϕ)$ is determined and the theory no longer possesses a free parameter or a free function, besides $G_{\rm N}$. For $V'(ϕ) = 0$ the theory reduces to general relativity (GR) with $G_N$ being the Newton's constant and $V=const.$ being the cosmological constant. For $V'(ϕ) \ne 0$, it is shown that gravity behaves differently from GR but that GR with $G_{\rm N}$ being the Newton's constant is recovered for weak gravity at distance and time scales sufficiently shorter than the scale associated with $V(ϕ)$. Therefore this theory provides the simplest framework of cosmology in which deviations from GR can be tested by observational data.
