Title: Cosmological perturbations in an effective and genuinely phantom dark energy Universe Show Chinese title

Title: 宇宙学扰动在一种有效且真正类 phantom 暗能量宇宙中

Abstract: We carry out an analysis of the cosmological perturbations in general relativity for three different models which are good candidates to describe the current acceleration of the Universe. These three set-ups are described classically by perfect fluids with a phantom nature and represent deviations from the most widely accepted $\Lambda$CDM model. In addition, each of the models under study induce different future singularities or abrupt events known as (i) Big Rip, (ii) Little Rip and (iii) Little Sibling of the Big Rip. Only the first one is regarded as a true singularity since it occurs at a finite cosmic time. For this reason, we refer to the others as abrupt events. With the aim to find possible footprints of this scenario in the Universe matter distribution, we not only obtain the evolution of the cosmological scalar perturbations but also calculate the matter power spectrum for each model. We have carried the perturbations in the absence of any anisotropic stress and within a phenomenological approach for the speed of sound. We constrain observationally these models using several measurements of the growth rate function, more precisely $f\sigma_8$, and compare our results with the observational ones. Show Chinese abstract

Abstract: 我们对广义相对论中的宇宙扰动进行了分析，针对三种不同的模型，这些模型是描述当前宇宙加速膨胀的良好候选模型。 这三种设置在经典上由具有幻影性质的完美流体描述，并代表了对最广泛接受的$\Lambda$CDM 模型的偏离。 此外，每种研究中的模型都会引发不同的未来奇点或突然事件，称为（i）大撕裂，（ii）小撕裂和（iii）大撕裂的小兄弟。 只有第一个被视为真正的奇点，因为它发生在有限的宇宙时间。 因此，我们将其他情况称为突然事件。 为了寻找这种情景在宇宙物质分布中的可能痕迹，我们不仅获得了宇宙标量扰动的演化，还计算了每个模型的物质功率谱。 我们在没有各向异性应力的情况下进行扰动，并采用现象学方法处理声速。 我们使用多种生长率函数的观测测量来对这些模型进行约束，更具体地说是$f\sigma_8$，并将我们的结果与观测结果进行比较。