Axially Symmetric Cosmic Strings in a Scalar-Tensor Theory

Axially symmetric cosmological models with cosmic string source are obtained in a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. A113, 467, 1985). The models obtained give us axially symmetric geometric (Nambu) string, p-string and Reddy string (Astrophys. Space Sci. 286, 2003b) in Saez-Ballester theory. Some physical properties of the models are also discussed.     

On Plane Symmetric Domain Walls and Cosmic Strings in Bimetric Theory

Plane symmetric thick domain walls and cosmic strings are considered in Rosen's (General Relativity and Gravitation 4, 435, 1973) bimetric theory of gravitation. It is shown that, in this theory, thick domain walls and cosmic strings do not exist. Hence, the vacuum solutions in both the cases are presented. PACS No.:98.80     

On Einstein–Rosen Cosmic Strings in a Scalar Tensor Theory of Gravitation

Explicit field equations of a scalar tensor theory of gravitation proposed by Saez and Ballester are obtained with the aid of Einstein–Rosen cylindrically symmetric metric in the presence of cosmic string source. The field equations being highly non–linear static and non–static cases have been considered separately. It is observed that in the static case the geometric strings do not exist while in the non–static case cosmological model does not exist in this theory.     

宇宙大尺度结构对星系形成和空间排列的影响

星系的空间排列以及指向并非随机的.星系的主轴和角动量与物质的大尺度分布存在一定的指向相关.这一方向的研究将可以促进我们对结构形成机制的认识,并提供一个独立的视角去检验星系形成过程中的环境效应.本文就相关问题做了详细的探讨.     

Superluminal Kinematics in the Milne Universe: Causality in the Cosmic Time Order

The causality of superluminal signal transfer in the galaxy background is scrutinized. The cosmic time of the comoving galaxy frame determines a distinguished time order for events connected by superluminal signals. Every observer can relate his rest frame to the galaxy frame, and compare so the time order of events in his proper time to the cosmic time order. In this way all observers arrive at identical conclusions on the causality of events connected by superluminal signals. The energy of tachyons (superluminal particles) is defined in the comoving galaxy frame analogous to the energy of subluminal particles. It is positive in the galaxy frame and bounded from below in the rest frames of geodesically moving observers, so that particle-tachyon interactions can be based on energy-momentum conservation. We study tachyons in a Robertson-Walker cosmology with linear expansion factor and open, negatively curved 3-space (Milne universe). This cosmology admits globally geodesic rest frames for uniformly moving observers, synchronized by Lorentz boosts. In this context we show that no signals can be sent into the past of observers. If an observer emits a tachyonic signal, then the response of a second observer can never reach him prior to the emission, i.e., no predetermination can occur. The proof is based on the positivity of tachyonic energy. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Global Structure of the Colliding Bubble Braneworld Universe

The one-brane Randall-Sundrum model offers an example of a model with an `infinite' extra dimension in which ordinary gravity is recovered at large distances and the usual (3+1)-dimensional cosmology at late cosmic times. This is possible because the `bulk' has the geometry of anti de Sitter space, the curvature length ℓ of which delineates the (3+1)-dimensional behavior at large distances from the (4+1)-dimensional behavior at short distances. This spacetime, however, possesses a past Cauchy horizon on which initial data must be specified in a natural and convincing way. A more complete story is required that singles out some set of initial conditions to resolve the `bulk' smoothness and horizon problems. One such complete story is offered by the colliding bubble braneworld universe, where bubbles filled with AdS ⁵ nucleate from dS ⁵ or M ⁵ through quantum tunnelling. A pair of such colliding bubbles forms a Randall-Sundrum-like universe in the future of the collision. Because of the symmetry of bubbles produced through quantum tunnelling, the resulting universe is spatially homogeneous and isotropic at leading order, and the perturbations at the next order are completely well defined and calculable. In this contribution we discuss the possible global structure of such a spacetime. This revised version was published online in July 2006 with corrections to the Cover Date.     

X-Raying the Star Formation History of the Universe

We discuss a new method for inferring the stellar mass of a distant galaxy of known redshift based on the combination of a near-IR luminosity and multiband optical photometry. The typical uncertainty for field galaxies with I<22 in the redshift range 0相似文献   

星系形成与宇宙大尺度结构

宇宙大尺度结构的形成与星系形成密切相关,前者的研究把星系基本上视为一质点,而星系形成研究涉及到其内部结构,宇宙大尺度结构形成有两种模式,由小到大与由大到小,这两种模式被交替使用（当然不同简单的重复）很重要的一个原因是星系形成研究的推动。     

宇宙大尺度结构中的双成份分布

本文讨论了星系及其系统的两种分布:具有分数维几何性质的自相似分布和无规则分布;由相关函数的归一化条件和观测资料推知这两种分布的成份比约为1:4。     

The Universe Evolution as Possible Mechanism of Formation of Galaxies and Their Clusters

The Kepler problem is studied in a space with the Friedmann-Lemaitre-Robertson-Walker metrics of the expanding universe. Cosmic evolution leads to decreasing energy of particles, causing free particles to be captured in bound states, so that the evolution of the universe can be treated as a possible mechanism of the formation of galaxies and clusters of galaxies. The cosmological model is considered where the evolution of the universe plays the role usually inscribed to cold dark matter.     

宇宙大尺度分形结构的一阶Kohmoto熵

已有观测证据表明宇宙大尺度结构是自相似或自仿射的分形分布，并已求出表征这两类分形的结构分数维。多分形热力学中提出的Ｋｏｈｍｏｔｏ熵函数建立了多重分形和热力学的形式类比。本文在三维球对称坐标系中求取了无标度区间ｒｏ≤ｒ≤Ｒ范围内宇宙大尺度自相似分形分布的一阶Ｋｏｈｍｏｔｏ熵函数，它对应于信息论中的信息底从热力学角度看，宇宙大尺度结构代表了某种有序结构，耗散自组织过程也许是导致这一有序结构的直接原因。     

The need for an energy-dependent torsion-coupling constant in the early Universe

We present arguments to show that torsion-coupling constant (which depends on energy asE ^–2) can pass through the values of the coupling constants of the other interactions during the evolution of the Universe. An energy-dependent torsion-coupling constant helps in a natural way to understand the ratios of the coupling strengths of the different fundamental interactions.     

The early Universe with quantum non-conformal fields

Models for the early Universe with the combined influence of scalar fields and vacuum polarization are discussed using phase plane portraints. The results concern the probability of the birth of the Universe, different de Sitter solutions and expressions for scalar perturbations.     

The Study of the Large-Scale Structure Evolution of the Universe by Radiospectroscopy Methods

On the basis of our theoretical speculations we propose to organize search observations of baryon structures at high redshifts (z > 5). We suggest a new observable strategy for the search of baryon structures in radiolines of simplest molecules OH and CH, which may produce the megamaser and gigamaser emission in very early epoches. The theoretical basis is the possibility of seed productions for baryon structures by a last relativistic phase transition in gas of pseudo-Gold-stone bosons at z ∼ 10-20. This revised version was published online in July 2006 with corrections to the Cover Date.     

空洞、纤维状大尺度结构形成的一个模型

本文用N-体数值模拟对标准宇宙的大尺度结构进行了研究,给出了一个能形成空洞、纤维状结构的模型。该模型意味着,密度扰动存在超团的特征尺度,并且,在较小的尺度上,扰动也没有全被抹平。