Title: Baryonic matter perturbations in decaying vacuum cosmology Show Chinese title

Title: 衰变真空宇宙学中的重子物质扰动

Abstract: We consider the perturbation dynamics for the cosmic baryon fluid and determine the corresponding power spectrum for a $\Lambda(t)$CDM model in which a cosmological term decays into dark matter linearly with the Hubble rate. The model is tested by a joint analysis of data from supernovae of type Ia (SNIa) (Constitution and Union 2.1), baryonic acoustic oscillation (BAO), the position of the first peak of the anisotropy spectrum of the cosmic microwave background (CMB) and large-scale-structure (LSS) data (SDSS DR7). While the homogeneous and isotropic background dynamics is only marginally influenced by the baryons, there are modifications on the perturbative level if a separately conserved baryon fluid is included. Considering the present baryon fraction as a free parameter, we reproduce the observed abundance of the order of $5\%$ independently of the dark-matter abundance which is of the order of $32\%$ for this model. Generally, the concordance between background and perturbation dynamics is improved if baryons are explicitly taken into account. Show Chinese abstract

Abstract: 我们研究了宇宙重子流体的扰动动力学，并确定了相应功率谱，对于一种宇宙项线性衰变到暗物质且与哈勃率成正比的$\Lambda(t)$CDM 模型。该模型通过Ia型超新星（SNIa）（Constitution 和 Union 2.1）、重子声波振荡（BAO）、宇宙微波背景（CMB）各向异性谱第一峰的位置以及大尺度结构（LSS）数据（SDSS DR7）的联合分析进行了检验。虽然均匀各向同性的背景动力学仅在一定程度上受到重子的影响，但如果包含一个单独守恒的重子流体，则在扰动层面上会有修改。将当前重子分数作为自由参数，我们重现了观测到的重子丰度约为$5\%$，这独立于对于该模型而言暗物质丰度约为$32\%$的情况。通常情况下，如果明确考虑重子，背景和扰动动力学之间的一致性会得到改善。