Showing papers on "Cosmology published in 1975"

Homogeneous Relativistic Cosmologies

Abstract: Addressing a variety of theoretical cosmological problems, and emphasizing a mathematical approach, this volume nicely complements Peebles' "Physical Cosmology" (Princeton Series in Physics, 1971). Ryan and Shepley have concentrated on the structure of models of the universe. By using a modern terminology that emphasizes the operator nature of vectors and tensors, as opposed to their components in a particular coordinate system, the authors develop modern tensor analysis to the point where it can be applied to general relativistic cosmology. They then use it to describe homogeneous cosmologies in considerable detail. Both students and researchers are likely to find these techniques especially useful.Among their subjects are: spaces with groups of motions; singularities; Taub-NUT-Misner space; Bianchitype models; Hamiltonian cosmology; and perturbations in anisotropic models. A brief section on observations is also included, as is a complete bibliography. A final section presents graded exercises that underscore the potential yet unrealized in this area of study.Originally published in 1975.The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

Structure and evolution of the universe.

Abstract: A can forming method and apparatus wherein cut-burrs of a can blank are removed from the ends thereof an adhesive film is stuck onto the preheated ends of the blank and, then, said ends are subjected to high-frequency induction heating for melting said films to join said ends together in such a manner as to prevent edge effect and associated deformations from occurring, thereby to form a lapped seam having a remarkably high adhesive strength substantially without pin-hole formation.

Spectrophotometry of faint cluster galaxies and the Hubble diagram - An approach to cosmology

Abstract: New spectrophotometric data are presented for large-redshift galaxies in clusters. A new approach to aperture corrections and the analysis of the Hubble diagram is outlined, including the explicit incorporation of evolutionary effects. The importance of selection effects on the usual methods of analysis are in principle overcome in the analysis, although the heterogeneity of the sample still makes conclusions about cosmology slightly suspect. Formal values of the deceleration parameter are derived under several sets of assumptions, yielding results between +0.33 and -1.27 with formal standard deviations of order 0.7.

Influence of Gravitation on the Propagation of Electromagnetic Radiation

Abstract: The existence of a general helicity-rotation coupling is demonstrated for electromagnetic waves propagating in the field of a slowly rotating body and in the Goedel universe. This coupling leads to differential focusing of circularly polarized radiation by a gravitational field which is detectable for a rapidly rotating collapsed body. The electromagnetic perturbations and their frequency spectrum are given for the Goedel universe. The spectrum of frequencies is bounded from below by the characteristic rotation frequency of the Goedel universe. If the universe were rotating, the differential focusing effect would be extremely small due to the present upper limit on the anisotropy of the microwave background radiation.

Cosmology and the Higgs mass

Abstract: It is noted that spontaneous symmetry treaking implies a finite cosmological term in the Einstein equation for gravity. The present theories of weak and e.m. interactions disagree violently with the experimental limit on such a term unless an ad-hoc counter curvature is introduced.

On emission lines in the cosmic gamma-ray background

Abstract: The composite spectrum of gamma-rays is calculated which results from the decay of Ni-56 to Co-56 to Fe-56 throughout the history of the universe. The results for several cosmological models are presented and compared with the Apollo 15 measurements at low resolution of the cosmic background. The radioactivity background is a significant fraction of the total, and several of its features may be detectable.-

White holes and high energy astrophysics

Abstract: The role of exploding objects in high-energy astrophysics is discussed Quantitative results are obtained for the simple case of the canonical white hole which explodes from a singularity and consists of pressure-free matter in the comoving frame of reference General relativity is used for calculating the dynamical results Applications to X-ray background, transient X-ray sources, γ-ray bursts and high energy cosmic rays are considered White holes of more general types are discussed in a qualitative manner

Turbulence in cosmology. I. The effect of the strong turbulence on the early evolution of the universe

Abstract: Principles of the theory of turbulence in relativistic cosmology are developed. By averaging Einstein's equations over stochastic fields a self-consistent system of equations is obtained which describes statistically: (1) the influence of the turbulence on the ‘basic state of the Universe (the background) on which the turbulence develops; (2) the behaviour of the turbulence on the background ‘distorted’ by it. By means of a qualitative study of exact equations in the region of a strong turbulence at an early stage of cosmological expansion conditions of the absence of singularity are found and the possibility of stationary solutions in the homogeneous, isotropic, on the average, Universe (the cosmological constantA=0) is shown. The rate of cosmological expansion increases if the energy density of the turbulence is positive, and decreases if it is negative. The latter alternative takes place if the absolute value of the energy density of excitations, which will change into potential motions in the future, exceeds the energy density of the remaining part of the turbulence.

Turbulence in cosmology. II. The asymptotic effect of collective excitations on the cosmological expansion of the homogeneous and isotropic, on the average, Universe

Abstract: At the stage of a weak turbulence the interactions between excitations are negligible, and potential, vortical and gravitational perturbations may be considered independent. In this approximation the analytical solutions to exact equations of the turbulence theory are found. It is shown that only such excitations whose effective equations of state do not coincide with those of matter do contribute to the deviation from the Friedmann law. At the stagep=1/3ε this involves potential and vortical turbulences. A model of the Universe from gravitational waves is constructed. The influence of the turbulence on the course of the expansion is essential till the beginning of, and probably during, the synthesis of light elements. The rate of cosmological expansion and gravitational instability decreases if the potential turbulence predominates over the vortical one, and increases in the opposite case.

Charge conjugation and Segal’s cosmology

Abstract: We show that the operation of charge conjugation (and hence alsoCPT) can be realized as an actual geometric transformation within the framework of Segal’s chronogeometric theory. We also discuss some geometric questions connected to the foundations of the chronogeometric theory.

Numerical examples from perturbation analysis of the mixmaster universe

Abstract: Tensor perturbation in a closed anisotropic empty (mixmaster) universe is studied. Numerical solutions of the perturbation equations for the lowest inhomogeneous mode are given for some characteristic regimes of the background dynamics. The mixmaster universe is shown to be stable in this mode against gravitational perturbations. Growth of perturbations in the contraction of the universe shows the characteristic mixmaster-type oscillatory approach to singularity.

Relativistic Hierarchical Cosmology. I: Derivation of a Metric and Dynamical Equations

Abstract: An account of hierarchical cosmology is given that is based on general relativity, being split up into three pieces for ease of assimilation. Part II will treat of specific solutions relevant to the observed Universe, while Part III compares these models with available empirical data in an effort to pick a model that agrees with observation. Part I derives a metric for a system based on the assumptions of (i) spherical symmetry about any local observer, (ii) a density distribution falling off as ϕ = ϕ0(t)r−2 from any local origin with the hierarchy delineated by step functions, (iii) the Universe was denser and more compact at some epoch in the past. These assumptions (Sections 1, 2) serve to derive a metric (Section 2) that allows of the definition of an effective scale factorS′(t) for Hubble's law, but which involves (Section 3) a curvature (k) and a parameter for measuring the radial coordinate (r/R0) that both vary with epoch:k=k(t), R0=R0(t). The metric reduces in a special case (k=constant,R0=constant,S′(t)=S(t) defined by the Friedmann equations) to that of a Robertson/Walker Universe. Spacetime in the hierarchy (Section 4) can be open or closed depending on the behaviour of the dust. The equations of motion (or the field equations, equivalently) yield two equations analogous to the Friedmann equations, but including terms in the time-derivative of the curvature and a space-variable density of matter. Relativistic hierarchical cosmology provides a wider field of possible investigation with a view to describing the Universe (Section 6) than do the conventional uniform Robertson/Walker models.

Evolution of galaxies and its significance for cosmology

Abstract: Possible effects on observational cosmology of star evolution in ordinary galaxies are described. Only Friedman models with zero cosmological constants are considered. Numerical models for elliptical galaxies are discussed. 46 references. (BJG)

On the Possibility of Nucleosynthesis in Any Matter-Antimatter Symmetric Cosmology

Abstract: In any matter-antimatter symmetric cosmology the primeval nucleosynthesis imposes a typical size of a region of matter (antimatter) much larger than the diffusion length of neutrons. Observational results on the abundances of cosmic deuterium and helium are used to evaluate how large it has to be.