In this paper, the cosmological perturbations of dynamical dark energy and dark matter, which interact non-gravitationally are studied. This dark energy–dark matter non-gravitational interaction is linearly dependent on the energy densities of dark components. However, in the interacting quintessence dark energy models with such type of interaction, the non-adiabatic instabilities of cosmological perturbations at radiation-dominated epoch arise. To avoid this problem, the model of dynamical dark energy was chosen as the basis. Here, the equation of state parameter of dark energy evolves in time but can be assumed constant at early epoch, so this model can be tuned in such a way that the non-adiabatic instabilities would not appear. The drawback of this cosmological model is that the energy densities of dark components can take the negative values for the certain range of interaction parameter, so the conditions for positivity of dark components densities were derived. Using obtained constraints on the model parameters, the impact of coupling parameter on modification of cosmological perturbations’ evolution is analyzed.

中文翻译：

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在辐射主导时期，动态暗能量与稳定的大尺度宇宙学扰动相互作用

本文研究了非引力相互作用的动态暗能量和暗物质的宇宙学扰动。这种暗能量-暗物质非引力相互作用线性依赖于暗成分的能量密度。然而，在具有这种相互作用的典型暗能量模型中，会出现辐射主导时期宇宙学扰动的非绝热不稳定性。为了避免这个问题，我们选择了动态暗能量模型作为基础。在这里，暗能量状态参数方程随时间演化，但可以假设在早期是恒定的，因此可以调整该模型，使非绝热不稳定性不会出现。这种宇宙学模型的缺点是暗成分的能量密度在一定范围的相互作用参数下可以取负值，因此推导了暗成分密度为正的条件。利用得到的模型参数约束，分析了耦合参数对宇宙学扰动演化修正的影响。