Fluid Inflation

流体动力学中的反常：基于变分原理的手性背景中的流

Anomalies in fluid dynamics: flows in a chiral background via variational principle

本文通过将变分原理扩展至与外部轴矢量势耦合，研究了电磁场和轴矢量势同时作用下的正压理想流体流，发现矢量和轴流的散度由量子场论中的手性反常控制。

On wormhole formation in $f(\textit{R}, \textit{T})$ gravity: varying Chaplygin gas and barotropic fluid

Formation of specific static wormhole models is discussed, by assuming an $f(\textit{R}, \textit{T}) = R + 2 λT$ extended theory of gravity, $T =- ρ+ P_{r} + 2P_{l}$ being the trace of the energy momentum tensor. In the first part, wormhole solutions are constructed imposing that the radial pressure admits an equation of state corresponding to a varying Chaplygin gas. Two forms for the varying Chaplygin gas are considered, namely $P_{r} = - B b(r)^{u}/ρ^α$ and $P_{r} = -B R(r)^{m}/ ρ^{α}$, respectively. In the second part, the wormhole models are constructed assuming that the radial pressure c…

Inflationary universe in fluid description

We investigate a fluid description of inflationary cosmology. It is shown that the three observables of the inflationary universe: the spectral index of the curvature perturbations, the tensor-to-scalar ratio of the density perturbations, and the running of the spectral index, can be compatible with the Planck analysis. In addition, we reconstruct the equation of state (EoS) for a fluid from the spectral index of the curvature perturbations consistent with the Planck results. We explicitly demonstrate that the universe can gracefully exit from inflation in the reconstructed fluid models. Furth…

Inflation in a viscous fluid model

We explore a fluid description of the inflationary universe. In particular, we investigate a fluid model in which the equation of state (EoS) for a fluid includes bulk viscosity. We find that the three observables of inflationary cosmology: the spectral index of the curvature perturbations, the tensor-to-scalar ratio of the density perturbations, and the running of the spectral index, can be consistent with the recent Planck results. We also reconstruct the explicit EoS for a fluid from the spectral index of the curvature perturbations compatible with the Planck analysis. In the reconstructed …

Singular inflation from generalized equation of state fluids

We study models with a generalized inhomogeneous equation of state fluids, in the context of singular inflation, focusing to so-called Type IV singular evolution. In the simplest case, this cosmological fluid is described by an equation of state with constant $w$, and therefore a direct modification of this constant $w$ fluid, is achieved by using a generalized form of an equation of state. We investigate from which models with generalized phenomenological equation of state, a Type IV singular inflation can be generated and what the phenomenological implications of this singularity would be. W…

Perturbations in some models of tachyonic inflation

In the present work an inflationary tachyon field model of the early universe is considered. Several cosmological effects produced by a particular potential in this tachyonic era are studied, under the approximation of slow-roll inflation. In particular, the evolution of the spectral index $n_s$ with time is obtained. The equations for the cosmological scalar perturbations are analytically solved in order to show that the power spectrum for small $k$ values is $P_ζ\sim 1/k^{\frac{1}{2}+ν_2}$, where $ν_2$ depends on the barotropic index $γ_0$. For large $k$ values we find that the power spectru…

宇宙学扰动的Action方法：物质占优的二阶度规

Action approach to cosmological perturbations: the 2nd order metric in matter dominance

利用理想正压流体与具有拉格朗日量[-（\partial导数）^2]^[（1+w）/2 w]的导数耦合标量场之间的等价性，研究了后暴胀演化过程中的非线性宇宙学扰动.由于这个拉格朗日量只是k-暴胀的一个特例，这种方法类似于从暴胀研究非高斯性的方法。我们使用这种方法直接推导出随动规范中物质占主导地位期间的二阶度规，作为原始暴胀微扰ζ的函数。转到泊松规范，我们恢复以前在文献中导出的度量。

Viscous fluid holographic inflation

A model of inflation produced by a viscous fluid is investigated and its compatibility with the holographic principle at the very early universe (as recently formulated for the holographic universe with a holographic cut-off radius) is demonstrated. Specifically, ensuing from the model, the corresponding scale factor and infrared cut-off are analytically calculated, which are taken to be the particle and future event horizon for inflation, respectively. Using them, the energy conservation law, in the holographic point of view, is obtained. In this way, total equivalence of viscous fluid inflat…

相互作用暗能量：两个标量场的一般宇宙学演化

Interacting dark energy: generic cosmological evolution for two scalar fields

本文研究了两个耦合标量场在正压流体（可以是物质或辐射）存在下具有任意相互作用项V_T（τ，\vp）的宇宙演化。正压流体和标量场之间的力只是引力。我们证明了动力学完全由三个参数L_i i = 1，2，3决定.我们确定所有的临界点，并研究其稳定性。我们找到了六种不同的吸引子解，并计算了相应的宇宙学参数。我们讨论的可能性有一个标量场的暗能量，而另一个可能是一个标量场红移的物质。

来自超光速粒子流体的膨胀？

Inflation from a Tachyon Fluid?

受Sen和Gibbons最近工作的启发，我们研究了由快子物质主导的平坦均匀宇宙的演化。特别是，我们分析了在一个单一的快子场的早期滚动的通货膨胀的必要条件。