We use linear perturbation theory to study perturbations in dynamical dark energy (DE) models. We compare quintessence and tachyonic DE models with identical background evolution. We rewrite the perturbation equations for quintessence and tachyonic models in a form that makes it easier to see that these models are very hard to distinguish in the linear regime, especially when the equation of state w is close to that of Λ (i.e. in the limit (1 + w) ≪ 1). We use cosmic microwave background data and parametric representations for the two models to illustrate that current observations cannot distinguish between models with the same background evolution. Further, we constrain tachyonic models with the Planck data. We do this analysis for exponential and inverse square potentials and find that the intrinsic parameters of the potentials remain very weakly constrained. In particular, this is true in the regime allowed by low redshift observations.

我们使用线性扰动理论来研究动态暗能量 (DE) 模型中的扰动。我们比较了具有相同背景演化的 quintessence 和 tachyonic DE 模型。我们以一种更容易看出这些模型在线性状态下很难区分的形式重写了精华和快子模型的扰动方程，特别是当状态方程w接近 Λ的方程时（即在极限(1 + w) ≪ 1)。我们使用宇宙微波背景数据和两个模型的参数表示来说明当前的观测无法区分具有相同背景演化的模型。此外，我们用普朗克数据约束了快子模型。我们对指数势和平方反比势进行了这种分析，发现势的内在参数仍然受到非常弱的约束。尤其是在低红移观测所允许的范围内，这是正确的。