论文标题
标量调节引力中准牛顿宇宙的扰动
Perturbations of quasi-Newtonian universes in scalar-tensor gravity
论文作者
论文摘要
在这项贡献中，我们考虑了$ f（r）$重力和标量张量理论之间的等效性，以研究$ 1 + 3 $协变形式的标量宇宙学扰动的演变，用于与不构造流体流的无剪切宇宙学粉尘模型的类别。 $ f（r）$重力被认为是Brans-Dicke型号的子类，我们概述了$ f（r）$ gravity和标量调整理论之间的等价性。我们使用$ 1 + 3 $协变形式主义来呈现协变线性的演化和约束方程。然后，我们得出了描述标量调节理论中准牛顿宇宙线性化场方程的一致演变的集成条件。最后，我们得出了准Newtonian宇宙的密度和速度扰动的演化方程。我们应用谐波分解，并通过考虑$ r^{n} $模型来探索物质密度对比的行为。我们引入了所谓的准静态近似，以研究小尺度上的近似溶液。通过应用对初始条件的某些假设，已经检查了短波长和长波长模式的物质密度对比度的生长。
In this contribution, we consider the equivalence between $f(R)$ gravity and scalar-tensor theories to study the evolution of scalar cosmological perturbations in the $1 + 3$ covariant formalism for the classes of shear-free cosmological dust models with irrotational fluid flows. The $f(R)$ gravity is considered to be a subclass of Brans-Dicke models, we gave an overview on the equivalence between $f(R)$ gravity and scalar-tensor theories. We use the $1 + 3$ covariant formalism to present the covariant linearised evolution and constraint equations. We then derive the integrability conditions describing a consistent evolution of the linearised field equations of quasi-Newtonian universes in the scalar-tensor theories of gravity. Finally, we derive the evolution equations for the density and velocity perturbations of the quasi-Newtonian universe. We apply the harmonic decomposition and we explore the behaviour of the matter density contrast by considering $R^{n}$ models. We introduce the so-called quasi-static approximation to study the approximated solutions on small scales. The growth of the matter density contrast for both short- and long- wavelength modes has been examined by applying certain assumptions of the initial conditions.
