标题： 子视界和准静态近似下的标量-矢量-张量理论的有效流体描述 显示英文标题

标题： An effective fluid description of scalar-vector-tensor theories under the sub-horizon and quasi-static approximations

摘要： 我们研究了具有二阶运动方程和张量传播速度等效于光速的纯量-向量-张量（SVT）理论。 在次视界和准静态近似下，我们找到了有效暗能量流体的解析公式，即声速、各向异性应力以及能量密度和压力。 我们利用一般性的解析流体描述，并表明可以设计出与背景上 $\Lambda$ 冷暗物质（CDM）退化但在晚期阶段引力强度为 $G_{\rm eff}<G_{\rm N}$ 且存在非零暗能量扰动的SVT宇宙学模型。 我们将SVT设计模型引入广泛使用的Boltzmann求解器CLASS中，从而使得能够通过天体物理观测来检验SVT模型。 我们的SVT模型的有效流体方法揭示了声速和各向异性应力的非平凡行为，这在当前宇宙参数（如 $H_0$ 和 $\sigma_8$）存在分歧的情况下非常值得进一步研究。 显示英文摘要

摘要： We consider scalar-vector-tensor (SVT) theories with second-order equations of motion and tensor propagation speed equivalent to the speed of light. Under the sub-horizon and the quasi-static approximations we find analytical formulae for an effective dark energy fluid, i.e., sound speed, anisotropic stress as well as energy density and pressure. We took advantage of our general, analytical fluid description and showed that it is possible to design SVT cosmological models which are degenerate with $\Lambda$CDM at the background level while having gravity strength $G_{\rm eff}<G_{\rm N}$ at late-times as well as non-vanishing dark energy perturbations. We implemented SVT designer models in the widely used Boltzmann solver CLASS thus making it possible to test SVT models against astrophysical observations. Our effective fluid approach to SVT models reveals non trivial behaviour in the sound speed and the anisotropic stress well worth an investigation in light of current discrepancies in cosmological parameters such as $H_0$ and $\sigma_8$.