New Implications of Lyman-alpha forest for Cosmology

由于宇宙微波背景（CMB）和大尺度结构（LSS）的观测，宇宙学已经进入了一个高精度的时代。虽然Lambda-CDM模型已被证实是最大尺度上宇宙学数据的有效描述，但仍有一些问题尚未解决，如暗物质的性质，加速膨胀的机制，中微子在宇宙学中的确切作用和行为，暴胀的能量尺度及其与基础理论的联系。这个建议的目的是解决这些问题的实验和理论方面，通过嵌入在莱曼-α森林的信息。一方面，我们将分析迄今为止最大的中等分辨率类星体光谱样本（来自BOSS和eBOSS项目），并辅以最新的一组高分辨率类星体光谱（来自VLT），以100级精度测量红移在2.0和4.6之间的莱曼α通量功率谱，范围从亚Mpc到数百Mpc。另一方面，我们将运行最先进的流体动力学模拟，其中包含我们想要测试的各种宇宙学模型的成分，我们将让它们与莱曼-阿尔法数据进行比较，以确定最能再现观测结果的参数。随着数据的高红移，我们将有机会获得结构的非线性演化的早期阶段，最适合捕捉急剧截止，温暖的暗物质对物质功率谱的影响。有了大尺度上的旋臂，我们也将能够测试出现的更平滑的截止，例如，在混合暗物质或共振产生的无菌中微子场景中，我们将用非标准暗物质约束各种模型，如相互作用的暗物质或轴子。次百万秒差距尺度上的功率谱的测量将使我们能够解决星系际介质的温度特性和宇宙学参数，如标量谱指数或中微子质量之间的内在简并。因此，除了暗物质的性质问题之外，我们将使用我们独特的莱曼-α数据样本，辅以最新的普朗克宇宙微波背景各向异性测量，以获得对中微子质量的最严格约束，达到我们可以确认或排除中微子质量最小倒序假设的极限（根据中微子振荡的最新数据，预测Mnu = 0.11eV）。最后，莱曼α森林提供了一个很好的机会来检查次CMB尺度上的物质功率谱的形状。最近的结果表明，莱曼-α和CMB测量之间存在着一种微小的张力，如果得到证实，这将对暴胀理论产生有趣的影响，或者指向新的物理学，如修正的引力或暗物质与其他成分之间的相互作用。

Cosmology has entered into an era of high precision, thanks to Cosmic Microwave Background (CMB) and Large Scale Structure (LSS) observations. While the Lambda-CDM model has been confirmed as a valid description of cosmological data on the largest scales, some issues remain unsolved, like the nature of Dark Matter, the mechanism responsible for the acceleration of the expansion, the exact role and behavior of neutrinos in cosmology, the energy scale of inflation and its connection with a fundamental theory. The objective of this proposal is to address these issues both on the experimental and on the theoretical fronts, via the information embedded in Lyman- alpha forests. On the one-hand, we will analyze the largest sample of medium-resolution quasar spectra available to date (from the BOSS and eBOSS projects), complemented by the most recent set of high- resolution quasar spectra (from VLT), to measure with percent-level precision the Lyman-alpha flux power spectrum at redshifts between 2.0 and 4.6, and over scales ranging from sub-Mpc to hundreds of Mpc. On the other hand, we will run state-of-the-art hydrodynamical simulations that incorporate the ingredients of various cosmological models that we want to test, and we will confront them to the Lyman- alpha data to determine the parameters that best reproduce the observations. With data to high redshift, we will have access to early stages of the non-linear evolution of structures, best suited to capture the sharp cut-off that warm dark matter impacts on the matter power spectrum. With the large lever-arm in scales, we will also be able to test the smoother cut-off that appears, for instance, in mixed-dark matter or resonantly-produced sterile neutrino scenarios, and we will constrain a variety of models with non-standard dark matter such as interacting dark matter or axions. The measurement of the power spectrum on sub-Mpc scales will allow us to address the intrinsic degeneracy between the temperature properties of the intergalactic medium and the cosmological parameters such as scalar spectral index or neutrino mass. Beyond the question of the nature of dark matter, we will therefore use our unique Lyman-alpha data sample, complemented by the latest Planck measurement of the cosmic microwave background anisotropies, to obtain the tightest constraint on neutrino mass, reaching the limit where we can confirm or exclude the minimal Inverted Hierarchy scenario for neutrino masses (predicting Mnu = 0.11eV given the latest data of neutrino oscillations). Finally, Lyman-alpha forests provide a very good opportunity to check the shape of the matter power spectrum on sub- CMB scales. Recent results indicate a small tension between Lyman- alpha and CMB measurements, which, if confirmed, would have interesting consequences for inflation theories, or point to new physics such as modified gravity or interactions between dark matter and other components.