Showing papers on "Cosmology published in 1968"
TL;DR: In this article, the authors studied the peeling-off behavior of the Friedmann model in an expanding, dust-filled Friedmann universe of negative curvature and found that the interaction with the matter modifies the ''peeling off'' behavior.
Abstract: Asymptotic expansions are used to study outgoing gravitational radiation in an expanding, dust‐filled Friedmann universe of negative curvature. It is found that the interaction with the matter modifies the ``peeling‐off'' behavior. A quantity is defined which is interpreted as the total mass of the source and the disturbance, and which monotonically decreases as gravitational radiation is emitted. The group of coordinate transformations that preserve the asymptotic form of the metric and the boundary conditions is the same as the isometry group of the undisturbed Friedmann model. This may indicate that no physical significance attaches to the extra transformations of asymptotically flat space which are not contained in the inhomogeneous Lorentz group.
454 citations
Book•
01 Oct 1968
TL;DR: In this paper, a presentation of the fundamentals of special relativity, general relativity, and cosmology with particular emphasis and development of the electromagnetic stress-energy tensor in special relativity is presented.
Abstract: : Relativity and Cosmology is a presentation of the fundamentals of special relativity, general relativity, and cosmology- with particular emphasis and development of (1) the electromagnetic stress-energy tensor in special relativity, (2) the poynting-Robertson effect, (3) the experimental basis for special-relativistic gravitational theories, (4) the geometric foundation for Reimannian geometry, (5) the derivation of the cosmological metric from group theory, (6) a discussion of cosmological models, (7) rotation of coordinate systems in general relativity, (8) electromagnetism in media in general relativity, (9) rotationally symmetric general-relativistic solutions, (10) Godel's cosmological model, and (11) geodesic precession.
315 citations
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TL;DR: In this paper, the authors discuss baryon inhomogeneity in early high density high temperature universe, and show that matter excess over antimatter occurs in early homogeneous high temperature universes.
Abstract: Matter excess over antimatter in early high density high temperature universe, discussing baryon inhomogeneity
39 citations
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TL;DR: A survey of the observational data, the theoretical tools for making postdictions, and the cosmological model which has evolved from them is given in this paper, where the necessity of a "big bang" origin of time and a detailed understanding of the history of our universe are discussed.
Abstract: During the past three years, theory and experiment in cosmology have largely linked up. Results are the necessity of a “big bang” origin of time, and a detailed understanding of the history of our universe. This article gives a crude survey of the observational data, the theoretical tools for making “postdictions”, and the cosmological model which has evolved from them.
TL;DR: It is widely believed that the microwave background radiation discovered by Penzias and Wilson had its origin in a hot, early phase of the expanding Universe as discussed by the authors, and it is claimed that this could explain the fact that the energy density of the 3° K radiation is very close to those of starlight, magnetic fields, turbulent gas motions and cosmic rays, all measured in the galactic disk.
Abstract: IT is widely believed that the microwave background radiation1–10 discovered by Penzias and Wilson had its origin in a hot, early phase of the expanding Universe. The possibility has recently been considered11,12, however, that it is instead a result of the thermalization of starlight by interstellar dust grains. It is claimed that this could explain the fact that the energy density of the 3° K radiation is very close to those of starlight, magnetic fields, turbulent gas motions and cosmic rays, all measured in the galactic disk, and also of the energy produced13 by the conversion from hydrogen to helium of one-third the mean density of visible galaxies—a fraction which corresponds to the ratio of helium to hydrogen in young stars14. A paper by Zeldovic and Novikov15 has already, in fact, considered and discounted this possibility, and the purpose of this communication is to draw attention to some difficulties particularly associated with the suggestions of Hoyle and Wickramasinghe11 and of Narlikar and Wickramasinghe12.
TL;DR: In this paper, a new approach to quantum electrodynamics establishes a strong connexion between local electdynamics and cosmology, and seems to support the steady state model of the universe.
Abstract: A fresh approach to quantum electrodynamics establishes a strong connexion between local electrodynamics and cosmology, and seems to support the steady state model of the universe.
TL;DR: In this article, a cosmological model with a pole at red-shift 17, deceleration parameter q0 = −14 and a density parameter σ0 = 0085 is presented.
Abstract: IN a previous communication1 I discussed the possibility of having a closed universe model with the pole at a red-shift z ≃ 17 One possible observation in such a universe would be images in opposite or near opposite directions to the original object, if the object is not too far from the pole I showed that this may happen for a few radio sources listed in the 4C radio catalogues2 Another possible observation is to look for radio sources opposite known quasars To illustrate such an investigation I will refer to a cosmological model with a pole at red-shift 17, deceleration parameter q0 = −14 and a density parameter σ0 = 0085 In this model objects must have lifetimes of the order of 1–10 × 109 yr to be seen in two directions, because of the difference in light travel time This lifetime is too long for a quasar, but it may be possible to observe the object in a pre-quasar or post-quasar stage as a radio source or even as a faint optical object
TL;DR: Early evolution of universe related to present upper bound of primordial black body gravitational radiation temperature was discussed in this paper, where the early evolution of the universe was related to the upper bound on the temperature of the black body.
Abstract: Early evolution of universe related to present upper bound of primordial black body gravitational radiation temperature
TL;DR: Galaxies may have arisen out of thermal fluctuations in early stages in the expansion of the universe as mentioned in this paper, which may explain the existence of galaxies in the early stages of our universe.
Abstract: Galaxies may have arisen out of thermal fluctuations in early stages in the expansion of the universe.
TL;DR: In this paper, the authors considered the analytical solution for the open cosmological model with both radiation and matter and showed that the Friedmann solution correspond either to pressureless matter alone or to radiation alone, where a(τ) is a scale factor of the line element and Am, Ar are constants.
Abstract: THE discovery1 of the cosmic background radiation has stimulated research on the cosmological model with both matter and radiation2. As usually used the Friedmann solutions correspond either to pressureless matter alone or to radiation alone Here a(τ) is a scale factor of the line element and Am, Ar are constants. These equations describe an open model with negative curvature. It seems reasonable to consider an open model because of a number of observational and theoretical arguments3. Here I consider some properties of the analytical solution for the open cosmological model containing both radiation and matter.
TL;DR: In this article, the authors examined various processes that contribute to the production of gravitons and gave an estimate of the cross-sections for their production by two photons that react in presence of a gravitational field.
Abstract: In order to calculate the density of gravitons in the universe, we examine various processes that can contribute to the production of gravitons and we give an estimate of the cross-sections for their production by two photons that react in presence of a gravitational field. We give also the cross-sections for the inverse processes, that is for the destruction of gravitons. After having examined other processes of production, in particular the production by close binary systems of stars, we find that in the case of the evolutionary universe, that is, in a universe with an age of ∼1018 s, the situation is far from equilibrium and the gravitons are still accumulating. At the present stage the mean density of gravitons in the whole universe seems to be ∼ 10−19 erg/cm3.
TL;DR: The gamma-ray astronomical data now available testify, however, against the possibility of the cosmic-ray storage during the stop phase of the Lemaitre cosmological model as mentioned in this paper.
Abstract: The simple argument is presented to show that the average energy density of cosmic rays in the Metagalaxy must be much smaller than in the Galaxy. This conclusion could, in principle, be not valid in the Lemaitre cosmological model. The gamma-ray astronomical data now available testify, however, against the possibility of the cosmic-ray storage during the ‘stop’ phase of the Lemaitre model. The measurements of the diffuse background gamma-ray intensity with energy exceeding 10 MeV could definitely solve this problem.