宇宙微波背景、暗物质及加速膨胀若干问题的研究

This project is concentrated on cosmology and related problems. Three main objects will be studied, they are cosmic microwave background radiation (CMB), dark matter and dark energy. It is the key to understand the evolution of universe to study these three objects and will favor the study of inflation, recombinition and cosmic accelerating expansion. On the one hand, we shall study CMB, especially on local statistics of CMB, the influence of noise and non-Gaussianity for CMB, etc. One the other hand, looking CMB on as a standing point, we shall extent the study to two directions. One connects inflation period of the early universe to study the primordial perturbation and the related observable effects, including the origin and the evolution of the seed of structures, the behavior of the power spectrum, the effect of non-Gaussian due to noise, the effect of primordial gravitational wave on the B mode of polarization. The other ends at the period of the first stars and the formation of structures, concentrating the reionization progress, the effect of annihilation of the dark matter particles and the properties of dark matter halo, etc. While the expansion of the universe is demonstrated accelerating now, and the physics is related to the dark energy. We shall study the parameterization of the EOS for dark energy, and place constraints on the dark energy models by performing a joint analysis with observational data including those of type Ia supernovae. The ΛCDM model and other cosmological models will be checked carefully based on observations. γ-ray burst cosmology will also be studied by promoting the accuracy of the method including improving the current standard candle relation, finding new available standard candle relation, and exploring new observational methods, etc. In 2011, three scientists were awarded the Nobel Prize "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae". Moreover, the data of Planck project will be released before long. We shall pay attention to the frontier all over the world and try to do a systematic research on CMB, dark matter, dark energy, and the relations among them.

本项目主要研究宇宙学及相关问题，研究对象是宇宙微波背景、暗物质和暗能量，以此来深入探讨暴胀、复合时代以及宇宙加速膨胀这三个宇宙演化的关键阶段。一方面研究宇宙微波背景（CMB），特别是其局域统计性质和不均匀的噪声对非高斯性的影响；另一方面，将研究向两端拓展，一端是极早期的暴胀时代，主要研究各种暴胀模型、原初扰动、结构种子的起源和演化行为、原初引力波及其观测效应等；另一端是恒星和结构的形成，主要研究暗物质湮灭对结构和再电离的影响、暗物质晕的相关性质等。而暗能量则是关系到后期宇宙加速膨胀的关键问题，重点研究暗能量状态方程的参数化及其对宇宙加速因子的影响、用Ia型超新星和其他观测数据限制暗能量模型、伽马暴宇宙学等。2011年度的诺贝尔物理奖授予了宇宙加速膨胀项目，PLANCK卫星的数据也将很快公布。本项目将密切关注国内外最新进展，争取对宇宙微波背景、暗物质、暗能量及其之间的关联作出比较系统的研究。

在该项目中我们的工作主要涉及三个方面，即暗物质、第一代恒星和宇宙加速膨胀/暗能量。（1）暗物质的湮灭或衰变会影响宇宙微波背景辐射的各向异性，因此CMB的数据可以用来限制暗物质粒子的性质。我们研究了Planck卫星的CMB数据对暗物质粒子的一些基本参数的限制；在一种超致密暗物质迷你晕的结构中，暗物质的湮灭会影响21cm背景信号，我们研究了该结构中暗物质的湮灭对21cm背景信号的贡献。（2）第一代恒星在我们对宇宙再电离的研究中起着非常重要的作用。我们通过N体数值模拟的方法，研究了使用高红移的GRB II 和DLA的观测来探测第一代恒星信号的可行性。（3）宇宙探针是研究宇宙膨胀历史和暗能量性质的重要工具，我们研究了各种宇宙探针并用它们（单独或者联合）限制了不同的宇宙学模型和暗能量的性质，我们研究了这些探针对不同宇宙学模型的区分能力。另外我们也研究了在相应数据限制中的一种人为偏差。