暗物质简介

暗物质是当代物理学和天文学面临的一大挑战.文章介绍了暗物质的发现历史,暗物质存在的观测证据,以及已知的暗物质的基本性质.还介绍了广受关注的暗物质的候选者,以及目前暗物质探测实验的进展.     

暗物质问题简介

暗物质的属性问题是当代物理学面临的一大挑战.文章简要回顾了暗物质的发现历史,已有的暗物质观测证据和粒子物理中的暗物质候选者以及暗物质丰度起源相关理论,还介绍了近年来暗物质的空间间接探测和地下直接探测及其在理论上研究的新进展.     

纷繁隐秘的暗世界

 暗物质的由来 暗物质的最佳候选者--弱作用大质量粒子（WIMPs） WIMP 粒子是暗物质的唯一候选者吗？ 暗作用力,隐藏的世界 暗物质和暗能量之间的联系     

暗物质候选者大观园

理论物理学家李政道把暗物质研究视为当代四大科学问题之一[1].在<暗物质与暗能量>一文[2]中曾简述了三个主要类别的暗物质候选者,本文除对这三类物质做必要的引申叙述外,还介绍多年来,一些理论工作者提出的各种形式的暗物质候选者,总称之为暗物质候选者大观园.     

暗物质及暗物质粒子探测

文章首先对暗物质的概念作了简单介绍,接着介绍了暗物质的发现过程和暗物质存在的证据等.随后,介绍了目前人们对暗物质粒子基本性质的理解和目前比较流行的暗物质模型,并解释了弱相互作用重粒子(WIMP)为什么获得人们最多的关注.文中还简单介绍了目前探测暗物质粒子的三种实验方法:对撞机探测法、直接探测法和间接探测法.最后,介绍了目前暗物质探测的最新进展,包括来自DAMA,CoGent,PAMELA,ATIC,Fermi等实验的最新结果.     

WIMPs 暗物质

 暗物质是21 世纪宇宙学和粒子物理研究的热点问题。WIMPs 是一种流行的暗物质粒子候选者,即weakly interacting massive particles 的缩写,译为“弱作用重粒子”。目前我国计划中的暗物质粒子探测实验项目都是围绕着WIMPs 暗物质开展的。本文将详细地阐述与WIMPs 暗物质相关的基本问题,并力图澄清一些易于误解的概念。     

怎样直接探寻暗物质

正探寻暗物质的含义顾名思义"暗物质",就是用任何波长的光,无论是极短波长的γ射线还是很长波长的无线电波都无法观察到的物质。当没有光线时,它是黑暗的,无法看到它;有光线时,它既不反射光,也不吸收光,是完全透明的,我们依然观察不到它。但是,自1993年以来,发现宇宙中存在暗物质的所有根据都是因为"引力"。因为这些暗物质与我们普通物质之间有"引力"作用,才使我们感知到暗物质的存在。暗物质不仅存在,而且在宇宙物质     

暗物质依然存在着

暗物质是神秘的不可见的物质,约占宇宙物质中的83％．暗物质使处于高速旋转的星系免于飞散,对暗物质的研究有助于我们了解宇宙的结构是如何形成的．     

基于DAMPE的暗物质间接探测研究进展

20世纪30年代天文学观测对标准宇宙模型提出了严峻挑战,为了调和观测数据与理论模型的矛盾,理论物理学家提出了暗物质理论;此后,实验物理学家据此摸索出了各种暗物质探测方案.本文将从暗物质概念的由来、暗物质基本性质、暗物质探测原理及方法和DAMPE在探测暗物质方面的最新进展几个方面展开介绍.重点以DAMPE的数据为基础,以电子谱分析为核心,在前人的研究基础上,对DAMPE数据和结果进行多层次、多方位的综合,进一步阐述了DAMPE电子谱中出现的TeV拐折和尖锐信号包含的深刻意义;最后依托研究过程中得到的一些信息,对未来暗物质探测实验提出一点看法和见解.     

暗物质研究新进展

 “暗物质”在现代天文学中指的是占有宇宙中绝大部分质量的、却不以我们可测的形式发光的物质形态。研究暗物质是现代宇宙学一个重要课题,暗物质的存在可以解释星系的一些反常动力学特征,及引力透镜等许多现象;暗物质的数量多少可以决定宇宙的膨胀可否一直进行下去,还可以从临界密度的角度检验暴胀宇宙论;而对暗物质的具体物质形态进行研究,则更是一个涉及多个学科领域的很有,吸引力的研究领域。     

Explaining the DAMA signal with WIMPless dark matter

WIMPless dark matter provides a framework in which dark matter particles with a wide range of masses naturally have the correct thermal relic density. We show that WIMPless dark matter with mass around 2–10 GeV can explain the annual modulation observed by the DAMA experiment without violating the constraints of other dark matter searches. This explanation implies distinctive and promising signals for other direct detection experiments, GLAST, and the LHC.     

Galactic searches for dark matter

For nearly a century, more mass has been measured in galaxies than is contained in the luminous stars and gas. Through continual advances in observations and theory, it has become clear that the dark matter in galaxies is not comprised of known astronomical objects or baryonic matter, and that identification of it is certain to reveal a profound connection between astrophysics, cosmology, and fundamental physics. The best explanation for dark matter is that it is in the form of a yet undiscovered particle of nature, with experiments now gaining sensitivity to the most well-motivated particle dark matter candidates. In this article, I review measurements of dark matter in the Milky Way and its satellite galaxies and the status of Galactic searches for particle dark matter using a combination of terrestrial and space-based astroparticle detectors, and large scale astronomical surveys. I review the limits on the dark matter annihilation and scattering cross sections that can be extracted from both astroparticle experiments and astronomical observations, and explore the theoretical implications of these limits. I discuss methods to measure the properties of particle dark matter using future experiments, and conclude by highlighting the exciting potential for dark matter searches during the next decade, and beyond.     

Do magnetic fields prevent mirror particles from entering the galactic disk?

Recently it has been suggested that magnetic fields prevent mirror particles from entering the galactic disk, thereby disfavouring the mirror dark matter explanation of the dark matter direct detection experiments. We show that mirror particle self interactions will typically randomize the directions of heavy mirror particles on length scales much shorter than their gyroradius. This means that heavy mirror particles are free to enter the galactic disk and consequently mirror dark matter remains consistent with all experiments and observations.     

Testing a new sterile neutrino dark matter candidate

A new class of sterile neutrino dark matter is suggested by an explanation for time variations in the solar neutrino flux in which coupling of sterile neutrinos to other matter is via a very small flavor off-diagonal transition magnetic moment, TMM. The dark matter sterile neutrino’s decay in the radiative channel then depends on the local magnetic field and the unknown value of the TMM. An interesting application of this model uses the DAMA/LIBRA claimed detection of dark matter (assuming they are observing the electromagnetic signal) to provide the decay rate in the Earth’s field, and hence the TMM value. That version of the model is then examined to see if it can be falsified by cosmic X-ray observations or by other direct detection experiments. Particularly the latter could provide a simple, definitive test of this dark matter candidate, which would bring concordance to these experiments.     

Some studies on dark energy related problems

In this work we perform some studies related to dark energy. Firstly, we propose a dynamical approach to explain the dark energy contents of the universe. We assume that a massless scalar field couples to the Hubble parameter with some Planck-mass suppressed interactions. This scalar field develops a Hubble parameter-dependent (thus time-dependent) vacuum expectation value, which renders a time-independent relative density for the dark energy and thus can explain the coincidence of the dark energy density of the universe. Furthermore, we assume that the dark matter particle is metastable and decays very late into the dark energy scalar field. Such a conversion of matter to dark energy can give an explanation for the starting time of the accelerating expansion of the universe. Secondly, we introduce multiple Affleck-Dine fields to the landscape scenario of dark energy in order to have the required baryon-asymmetrical universe. PACS: 95.36. + x, 95.35. + d     

Higher-order theories of gravity matched with large-scale structure and cosmological observations

The so-called f(R)-gravity could, in principle, explain the accelerated expansion of the Universe without adding unknown forms of dark energy/dark matter, but more simply extending the general relativity by generic functions of the Ricci scalar. However, as a part of several phenomenological models, there is no final f(R)-theory capable of fitting all the observations and addressing all the issues related to the presence of dark energy and dark matter. Astrophysical observations are pointing out huge amounts of “dark matter” and “dark energy” needed to explain the observed large-scale structures and cosmic accelerating expansion. Up to now, no experimental evidence has been found, at a fundamental level, to explain such mysterious components. The problem could be completely reversed considering dark matter and dark energy as “shortcomings” of general relativity.     

Cryptobaryonic dark matter

It is proposed that dark matter could consist of compressed collections of atoms (or metallic matter) encapsulated into, for example, 20 cm big pieces of a different phase. The idea is based on the assumption that there exists at least one other phase of the vacuum degenerate with the usual one. Apart from the degeneracy of the phases we only assume standard model physics. The other phase has a Higgs vacuum expectation value appreciably smaller than in the usual electroweak vacuum. The balls making up the dark matter are very difficult to observe directly, but inside dense stars may expand absorbing the star and causing huge explosions (gamma ray bursts). The ratio of dark matter to ordinary matter is expressed as a ratio of nuclear binding energies and predicted to be about 5.     

Unified origin of baryons and dark matter

We investigate the possibility that both the baryon asymmetry of the universe and the observed cold dark matter density are generated by decays of a heavy scalar field which dominates the universe before nucleosynthesis. Since baryons and cold dark matter have common origin, this mechanism yields a natural explanation of the similarity of the corresponding energy densities. The cosmological moduli and gravitino problems are avoided.     

The birth and death of a universe

This letter is meant to be a brief survey of several recent publications providing a simple, sequential explanation of dark energy, inflation, and dark matter. These paragraphs lead to an intuitive and qualitative picture of the why and the how of the Big Bang, and thence to a possible understanding of the birth and death of a universe.     

Supernovae and properties of matter in the densest and most rarefied states

An overview of the relationship between the astrophysics of supernovae and fundamental physics is given. It is shown how astronomical observations of supernovae are used to determine the parameters of matter in the most rarefied states (“dark energy”); it is also revealed that the mechanism of supernovae explosion is related to the properties of matter in the densest states. The distinction between thermonuclear and collapsing supernovae is explained. Some problems that arise in the theory of powerful cosmic explositions—supernovae and gamma-ray bursts—and which require new physics for solving them are indicated.