质疑暴涨宇宙模型

 WMAR的观测结果强有力地支持了暴涨宇宙模型(见本刊2004年第1期张新民同志的文章《反物质和暗能量》)。但今年2月,几个观测小组却对此提出质疑。两个小组用地基射电望远镜测量不同天区的温度时发现:小天区温度的起伏比较大天区温度的起伏为小而对于大得多的天区温度的起伏反而变小了。这不符合暴涨学说的预见:温度的起伏与我们所注视天区的大小无关。在智利阿塔卡马研究宇宙背景成像仪(CosmicBackgroundImager简称CBI)数据的加拿大多伦多大学的邦德(DickBond)认为上述两个反常现象的结论未考虑到统计的重要性,两者出现的几率均只约为1/20.     

宇宙演化与热寂说

在已成熟的宇宙演化理论的基础上,文章作者重新讨论了Clausius提出的热寂问题.宇宙演化指其组分和宏观面貌的变化.主要是微观结团和宏观结团.从物理原理上讲,这些结团过程是力学的,而不是热力学的.力学过程一定程度上破坏了原有的热平衡,热力学则倾向于恢复热平衡.所有已知的物理规律,包括热力学在内,都在宇宙演化中起着它应起的作用.作为后果,宇宙的熵在演化中一直是增加的.克劳修斯把热力学第二定律用于宇宙是正确的.可是他认为宇宙的熵会极大化并不正确.这是因为在演化过程中会出现组分粒子的退耦.     

宇宙演化与热寂说

在已成熟的宇宙演化理论的基础上,文章作者重新讨论了Clausius提出的热寂问题.宇宙演化指其组分和宏观面貌的变化.主要是微观结团和宏观结团.从物理原理上讲,这些结团过程是力学的,而不是热力学的.力学过程一定程度上破坏了原有的热平衡,热力学则倾向于恢复热平衡.所有已知的物理规律,包括热力学在内,都在宇宙演化中起着它应起的作用.作为后果,宇宙的熵在演化中一直是增加的.克劳修斯把热力学第二定律用于宇宙是正确的.可是他认为宇宙的熵会极大化并不正确.这是因为在演化过程中会出现组分粒子的退耦.     

宇宙中的幽灵――暗物质

爱因斯坦曾经有一句名言：“宇宙最不可理解的是它竟然是可以理解的!”自从爱因斯坦写下他的可以理解宇宙的方程以及做出关于“宇宙是可以理解的”这个惊异的发现至今已有近一百年。     

第四讲 暴涨宇宙学的研究与进展

文章简单介绍了标准（大爆炸）宇宙模型的成功和困难,着重介绍了暴涨宇宙学的研究历史和最近的进展,并展望了今后人们可能的关注方向     

决定宇宙演化前景的判据

 1998年6月3日,从清晨5时起,中央电视台连续3小时直播美国发现号航天飞机运载α磁谱仪升空实况的同时,还向大家介绍了许多宇宙学的知识。宇宙学的发展大大深化了人类对宇宙起源和演化的认识,为了解物质结构和相互作用提供了新的统一图景。     

第四讲暴涨宇宙学的研究与进展

文章简单介绍了标准(大爆炸)宇宙模型的成功和困难，着重介绍了暴涨宇宙学的研究历史和最近的进展，并展望了今后人们可能的关注方向     

宇宙常数的Bulk流形的起源

关于宇宙常数问题是个至今没有解决的问题, 它的来源至今还没有一个共识. 从额外维的流形出发, 给出了宇宙常数的,bulk,流形起源的理论, 得到了不同情况下宇宙常数的取值和宇宙常数随时间演化的函数, 并且得到了可拟合现代天文观测的宇宙常数.     

“暗宇宙”之谜

 夜幕降临,星光灿烂,银河、星斗与皎洁的月光交辉相映,编织出美丽的夜空,这就是我们从小获得的知识:恒星、星云、星系……构成的浩瀚宇宙。然而,这只是个错觉,我们的宇宙实际上是“暗无天日”的,这就是2003年过去一年最新的科学成就:宇宙是黑暗的,或者说是个“暗宇宙”(请参阅封二精美彩图)。什么是暗宇宙?那是指组成宇宙的绝大多数物质和能量是不可见的,发光的物质和辐射只占宇宙物质的极小部分,这种不可见的物质和能量称为暗物质和暗能量。根据最新的测量,暗能量和暗物质合计占宇宙质量密度的96%,而我们熟知的恒星、星系等发光物质或重子物质仅仅只占4%。     

位错密度的演化动力学方程

将位错的增殖、淹没与相互反应看作化学反应,位错在热激活作用下具有扩散性质。因此,位错系统是一个反应-扩散系统。依据自组织理论,给出了两个位错密度演化动力学方程,当系统发生结构失稳之后,第一个方程变成第二个方程;第一个方程含有对称性破缺,按Higgs机制将发射偶极子。     

Relic Density of Asymmetric Dark Matter in Modified Cosmological Scenarios

We discuss the relic abundance of asymmetric Dark Matter particles in modified cosmological scenarios where the Hubble rate is changed with respect to the standard cosmological scenario. The modified Hubble rate leaves its imprint on the relic abundance of asymmetric Dark Matter particles if the asymmetric Dark Matter particles freeze-out in this era. For generality we parameterize the modification of the Hubble rate and then calculate the relic abundance of asymmetric Dark Matter particles and anti-particles. We find the abundances for the Dark Matter particles and anti-particles are enhanced in the modified cosmological models. The indirect detection signal is possible for the asymmetric Dark Matter particles due to the increased annihilation rate in the modified cosmological models. Applying Planck data, we find the constraints on the parameters of the modified cosmological models.     

Cosmological Constant and Stability of the Cosmological Models

The importance of cosmological constant for the cosmological models is given. The variations of the cosmological model for parameters λ and k were discussed respectively. Near λ = 0, the cosmological model is unstable with the change of λ, and near λ = β = 0, the cosmological model is unstable with the change of k. So when we consider the stable cosmological model, we must consider the nonzero cosmological constant.     

New Method of Generating Exact Inflationary Solutions in Generalized Einstein Theories

We discuss the general approach to finding exact inflationary solutions in generalized Einstein theories. These solutions are found by taking the Hubble parameter directly as a function of the field and then determining the evolution of the expansion scale factor and the potential from it. This method allows the full dynamic behavior of the field to be investigated in terms of the function H() without needing to assume that friction terms in the field equations dominate or that the field's kinetic energy is negligible.     

Cosmological Relics of the High Energy Cold Dark Matter Particle in the Universe

We demonstrate that if the universe is dominated by the massive cold dark matter, then besides the generally believed thermal distribution of the dark matter relics, there may exist some very energetic nonthermal relics of the dark matter particles in the universe from some unknown sources, such as from decay of supermassive X particle released from topological defect collapse or annihilation. Very interesting, we point out that these high energy dark matter particles may be observable in the current and future cosmic ray experiments.     

String Cosmological Solutions with O(d,d) Duality Symmetry and Matter Coupling

The duality properties of string cosmology model with negative energy matter are investigated by means of renormalization group equation,the cosmological solutions with exotic matter coupling are obtained in D=d+1 dimensional space-time.These inflation-power solutions can describe accelerated and decelerated process in the early universe,and the duality solutions can be generated through O(d,d) transformations.     

Kinematics of a Spacetime with an Infinite Cosmological Constant

A solution of the sourceless Einstein's equation with an infinite value for the cosmological constant is discussed by using Inönü–Wigner contractions of the de Sitter groups and spaces. When , spacetime becomes a four-dimensional cone, dual to Minkowski space by a spacetime inversion. This inversion relates the four-cone vertex to the infinity of Minkowski space, and the four-cone infinity to the Minkowski light-cone. The non-relativistic limit c is further considered, the kinematical group in this case being a modified Galilei group in which the space and time translations are replaced by the non-relativistic limits of the corresponding proper conformal transformations. This group presents the same abstract Lie algebra as the Galilei group and can be named the conformal Galilei group. The results may be of interest to the early Universe Cosmology.     

Solution to the Cosmological Constant Problem by Gauge Theory of Gravity

Based on geometry picture of gravitational gauge theory, the cosmological constant is determined theoreti-cally. The cosmological constant is related to the average energy density of gravitational gauge field. Because the energydensity of gravitational gauge field is negative, the cosmological constant is positive, which generates repulsive force onstars to make the expansion rate of the Universe accelerated. A rough estimation of it gives out its magnitude of theorder of about 10-52m-2, which is well consistent with experimental results.     

Cosmological constant from quarks and torsion

We present a simple and natural way to derive the observed small, positive cosmological constant from the gravitational interaction of condensing fermions. In the Riemann‐Cartan spacetime, torsion gives rise to the axial–axial vector four‐fermion interaction term in the Dirac Lagrangian for spinor fields. We show that this nonlinear term acts like a cosmological constant if these fields have a nonzero vacuum expectation value. For quark fields in QCD, such a torsion‐induced cosmological constant is positive and its energy scale is only about 8 times larger than the observed value. Adding leptons to this picture could lower this scale to the observed value.     

Solution to the Cosmological Constant Problem by Gauge Theory of Gravity

Based on geometry picture of gravitational gauge theory, the cosmological constant is determined theoreti-cally. The cosmological constant is related to the average energy density of gravitational gauge field. Because the energy density of gravltatlona] gauge field is negative, the cosmological constant is positive, which generates repulasive force on stars to make the expansion rate of the Universe accelerated. A rough estimation of it gives out its magnitude of the order of about 10^52m^-2, which is well consistent with experimental results.