论文标题
通货膨胀和宇宙学（不可）在单模型重力中
Inflation and the cosmological (not-so) constant in unimodular gravity
论文作者
论文摘要
我们提出了一种在早期宇宙中产生通货膨胀阶段的机制，而无需诉诸任何类型的标量场。取而代之的是，这种加速的扩展是由一个动态的“宇宙常数”驱动的，这是在非模块性重力的框架中驱动的。依赖时间的宇宙常数可能与由于其限制性扩散不变性而自然产生的能量扩散项有关。我们得出任何类型的扩散所需的通用条件，以产生逼真的通货膨胀时期。此外，对于通货膨胀的给定参数化（就哈勃流量功能而言），我们以这样的方式展示了如何构建相应的扩散术语，以使通货膨胀与随后的辐射占据主导的时代之间的平滑过渡，因此重新加热是自然的。原始光谱是通过考虑与标准流体动力学相关的不均匀扰动（建模为单个超相关流体），从而在通货膨胀阶段获得的原始光谱。我们证明所产生的频谱等同于传统通货膨胀模型中获得的频谱，也与扩散项的特定形式无关。此外，我们分析了识别可变宇宙常数（负责通货膨胀膨胀）的可行性，并具有当前观察到的值。
We propose a mechanism for generating an inflationary phase in the early universe without resorting to any type of scalar field(s). Instead, this accelerated expansion is driven by a dynamical "cosmological constant" in the framework of unimodular gravity. The time dependent cosmological constant can be related to an energy diffusion term that arises naturally in unimodular gravity due to its restrictive diffeomorphism invariance. We derive the generic conditions required for any type of diffusion to generate a realistic inflationary epoch. Furthermore, for a given parameterization of inflation (in terms of the Hubble flow functions), we show how to construct the corresponding diffusion term in such a way that a smooth transition occurs between inflation and the subsequent radiation dominated era, hence reheating proceeds naturally. The primordial spectrum is obtained during the inflationary phase by considering inhomogeneous perturbations associated to standard hydrodynamical matter (modeled as a single ultra-relativistic fluid). We demonstrate that the resulting spectrum is equivalent to that obtained in traditional inflationary models, and is also independent of the particular form of the diffusion term. In addition, we analyze the feasibility of identifying the variable cosmological constant, responsible for the inflationary expansion, with the current observed value.
