Cosmic Ether

A prerelativistic approach to particle dynamicsis explored in an expanding Robertson–Walkercosmology. The receding galactic background provides adistinguished frame of reference and a unique cosmictime. In this context the relativistic, purelygeometric space-time concept is criticized. Physicalspace is regarded as a permeable medium, the cosmicether, which effects the world-lines of particles andrays. We study in detail a Robertson–Walkeruniverse with linear expansion factor and negativelycurved, open three-space; we choose the permeabilitytensor of the ether in such a way that the semiclassicalapproximation is exact. Galactic red-shifts depend on therefractive index of the ether. In the local Minkowskianlimit the ether causes a time variation of mass, whichscales inversely proportional to cosmic time. In the globally geodesic rest frames of galacticobservers the ether manifests itself in an unboundedspeed of signal transfer, in bifurcations ofworld-lines, and in time inversion effects.     

Cosmic deuterium

The knowledge of the primordial deuterium to hydrogen ratio provides one of the most reliable tests of the early Universe nucleosynthesis models and a direct estimate of the cosmic baryon density. Evaluations have been traditionally made using D/H estimations in the interstellar medium, extrapolated backwards in time with the use of galactic evolution models. Direct primordial D/H measurements have been carried out only recently in the direction of quasars. These measurements of deuterium abundances along with observations made in the solar system and in the interstellar medium are presented.New results that indicate spatial variations of the deuterium abundance in the interstellar medium at the level of 50% over scales possibly as small as 10 pc, may question our global vision of deuterium evolution until the causes for the origin of these variations are understood. With a conservative point of view, observations thus suggest that the primordial D/H value should be within the range 1. × 10⁻⁵−3. × 10⁻⁴, leading to a relatively low baryon content Universe.Since the actual evolution of deuterium from primordial nucleosynthesis to now is not known in details, more observations, hopefully to be made with the Hubble Space Telescope, FUSE the Far Ultraviolet Spectroscopic Explorer (launched in 1999). or from the ground with the largest telescopes (Keck, VLT,), should reveal the evolution of that key element, and better constrain its primordial abundance.     

Cosmic jets

We discuss time-dependent gravitational fields that “accelerate” free test particles to the speed of light resulting in cosmic double-jet configurations. It turns out that complete gravitational collapse along a spatial axis together with corresponding expansion along the other two axes leads to the accelerated motion of free test particles up and down parallel to the collapse axis such that a double-jet pattern is asymptotically formed with respect to the collapsed configuration.     

Cosmic lacunarity

The present distribution of galaxies in space is a remnant of their formation and interaction. On a large enough scale, we may represent the galaxies as a set of points and quantify the structures in this set by its generalized dimensions [Beck and Schlogl, Thermodynamics of Chaotic Systems (Cambridge University Press, Cambridge, 1986); Paladin and Vulpiani, Phys. Rep. 156, 147 (1987)]. The results of such evaluation are often taken to be evidence of a fractal (or multifractal) distribution of galaxies. However, those results, for some scales, may also reveal the presence of singularities formed in the gravitational processes that produce structure in the galaxy distribution. To try to make some decision about this issue, we look for the more subtle galactic lacunarity. We believe that this quantity is discernible in the currently available data and that it provides important evidence on the galaxy formation process. (c) 1997 American Institute of Physics.     

宇宙核钟

以很长半衰期 ( 4 2× 1 0 9a)的 β-衰变的187Re-187Os核对作为大尺度的宇宙核钟来量度宇宙的年纪 ,是近代天文学与核物理学相结合的又一典范 .这种宇宙时钟是利用裸核187Re与它的衰变子体187Os同位素在共生矿中天然含量的比值来测定时间的 .利用187Re裸核的半衰期通过核物理计算可对中性 187Re的半衰期进行修定.To the great scale of the universe age, 187 Re- 187 Os isotopic pair, which have very long half life, was used as a cosmic nuclear clock of cosmochronometr. It is a typical relationship between modern astronomy and nuclear physics. The neutral isotope abundance ratio of 187 Re over daughter nucleus 187 Os in common growth mineral can be used as the clock to measure the time. After the 75 electrons in all shells of 187 Re were stripped ...     

Cosmic lorentz transformation

In special relativity the Lorentz transformation gives the substitutions for distances and time measurements in two coordinate systems moving relative to each other with a constant velocity. We derive the corresponding transformation for cosmology that connects coordinate systems in different locations and measuring distances and red shifts.     

Cosmic X-ray astronomy

The results obtained from observations of the celestial x-radiation over the past nine years are reviewed. Emphasis is placed on the study of the discrete sources, particularly those which have been identified with astronomical objects known from optical and radio studies. The isotropic background x-radiation is dealt with briefly, and the theories which account for x-ray production on the astronomical scale are mentioned where applicable. Finally, the observations needed to further advance this exciting subject are discussed.     

宇宙质心参考系

根据实际天文观测论述了膨胀着的宇宙系统的时间可以与空间分开来讨论;宇宙的空间是平直的。在宇宙质心坐标系中,由背景辐射温度、宇宙密度和宇宙半径（最远星系的距离）3个观测数据计算了宇宙这个引力系统的总能量,结果表明系统是一个引力束缚态,将来会收缩。在均匀分布的初始条件下计算了收缩过程,这是同步自由落体过程。在宇宙的膨胀过程与其收缩过程对称的假设之下,建立膨胀时间与背景辐射温度的一对一的对应关系。According to astronomical observation we point out that the time of our expanding cosmic system can be discussed separating from the space. And the space in our universe is flat. In the cosmic center-of-mass frame（CCF）, based on the temperature of CMBR, the cosmic density and the cosmic radii, the distance of the farmost galaxy, the total energy of our universe asa gravitation system has been calculated. It shows that our universe is in a gravitational bound state, and it will contract. In CCF the contracting progress is a synchronized freely falling body under initial condition of uniform distribution. Uder assumption of the symmetry of cosmic expanding and contracting progresses, th one-to-one correspondence of the expanding time to the temperature of CMBR can be obtained.     

Cosmic superstrings II

Modern string theory provides a rich array of objects which could potentially appear as cosmic strings in our observable four-dimensional universe. However, there are many possible decay modes which would prevent the appearance of such strings. We investigate the conditions under which metastable strings can exist, and we find that such strings are present in many models. Hence cosmic strings give a potentially large window into string physics. To cite this article: E.J. Copeland et al., C. R. Physique 5 (2004).

Résumé

La théorie moderne des supercordes fournit un choix riche d'objets qui pourraient potentiellement apparaître en tant que cordes cosmiques dans notre univers quadridimensionnel observable. Cependant, il y a beaucoup de modes possibles de désintégration qui empêcheraient l'apparition de telles cordes. Nous étudions les conditions dans lesquelles des cordes métastables peuvent exister, et nous constatons que de telles cordes sont présentes dans beaucoup de modèles. Par conséquent les cordes cosmiques ouvrent une fenêtre potentiellement grande vers la physique des supercordes. Pour citer cet article : E.J. Copeland et al., C. R. Physique 5 (2004).     

Cosmic phase transitions

The sequence of phase transitions during the hot history of the universe is followed within a phenomenological framework. Particular emphasis is put on the QCD confinement transition, which is at reach under earth laboratory conditions. A tepid inflationary scenario on the GUT scale with bubble growth at moderate supercooling is discussed.     

Cosmic gamma-ray bursts

All aspects of cosmic gamma-ray bursts are reviewed. First, instrumentation and experimental technique are briefly covered. Then the observable burst properties are described, and empirical classification schemes are offered. Searches for coinciding bursts at other frequencies are enumerated. The observed spatial distribution of the burst sources is given, as well as various theoretical interpretations. A section is devoted to the unusual gamma-ray burst of March 5, 1979; its features are compared to more typical events and analyzed for insights into burst origins. Theoretical models for gamma-ray bursts are considered in general, and then examined in more detail under the categories of extragalactic models, accretion onto compact objects, thermonuclear explosions, flare models, and exotic models.     

Cosmic chiral vortices

The review is devoted to cosmic chiral vortices (strings) and their possible role in the evolution of the early Universe. An exact cylindrically-symmetric solution to Einstein equations was obtained within the SU(2) sigma model for a configuration with a topological charge of the degree type. The linearized stability of the solution with respect to radial perturbations is proven by Lyapunov’s direct method. The metric found corresponds to the conical type with an angular deficiency proportional to the topological charge or the linear mass density of the vortex. The ray deflection angle close to the angular deficiency (the gravitational lens effect) was determined by direct integration of geodesic equations for the light ray orthogonal to the vortex. A gauge generalization of the model was considered involving the axially symmetric Yang-Mills field. In the approximation of the large topological charge, a solution with proper longitudinal magnetic field was obtained and the effect of a decrease in the vortex energy was found. The effect of closing the string was also considered in the approximation of the large closure radius. To this end, the toroidal moment of a closed string was calculated and an energy correction caused by the Skyrme term.     

宇宙磁场

磁场在宇宙中无处不在,贯穿各种天体。磁场对天体形成、辐射和演化起重要作用,也是宇宙线研究的基础。以前人们对宇宙磁场的理解主要是来自对地球和太阳磁场的测量和物理解释。近20年来,对宇宙更大尺度天体的磁场测量取得很大进展：发现了银河系具备沿着银河旋臂的几万光年尺度磁场,强度为2—4 μG;发现了银河系晕里具有环向磁场,在银道面上下方向相反;发现了银河系中心有极向磁场的观测证据;发现了邻近旋涡星系可能具有万光年尺度磁场的证据;发现了星系团几千万光年范围内磁场存在的证据。宇宙学模拟也显示在宇宙超大纤维结构中应该有磁场存在。这些磁场可能都是宇宙早期产生并在天体形成和演化过程中得以发扬光大。