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Showing papers on "Cosmology published in 1970"


Journal ArticleDOI
TL;DR: In this article, an oscillatory approach to a singular point in the relativistic cosmology is presented, where the point is represented as a point in a circle of light.
Abstract: (1970). Oscillatory approach to a singular point in the relativistic cosmology. Advances in Physics: Vol. 19, No. 80, pp. 525-573.

1,305 citations



Journal ArticleDOI
TL;DR: In this paper, the authors set upper limits to the amount of antimatter in the universe, the parameters of primaeval turbulence, and the adiabatic fluctuation spectrum for small masses.
Abstract: Heating of the primaeval plasma prior to the epoch of recombination results in distortions in the Rayleigh-Jeans region of the microwave relic radiation spectrum (λ∼1–60 cm, or more exactly λ=2.5Ω−7/8 cm). The present observational data allow limits to be set to such energy injection from which follow upper limits to (a) the amount of antimatter in the universe; (b) the parameters of primaeval turbulence; and (c) the adiabatic fluctuation spectrum for small masses (M<1011M⊙).

205 citations



Journal ArticleDOI
27 Feb 1970-Science
TL;DR: For example, the authors showed that the large-scale distribution of galaxies most of the time is homogeneous and isotropic, and most astonomers believe that the expansion of the universe proceeds at a uniform rate measured by the Hubble constant.
Abstract: Once upon a time philosophers and cosmographers insisted that the motions of the planets must be circular and uniform. An irrelevant aesthetic concept of ‘perfection’ and a more valid mathematical need for simplicity were at the root of this long-held error. Nowadays, theoretical cosmologists insist that the large-scale distribution of galaxies most be homogeneous and isotropic, and most astonomers believe that the expansion of the universe is linear and isotropic and that it proceeds at a uniform rate measured by the Hubble ‘constant’ H.1, 2

192 citations


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method for determining the extragalactic distance scale for nearby galaxies and searching for exceedingly distant clusters where the redshift is large, to measure both of these numbers to a precision of 15%.
Abstract: AS RECENTLY AS THE 1950's about all that observational cosmology had succeeded in establishing was that galaxies exist and the universe expands. But beginning in the 1960's a flood of new discoveries has enriched our picture of the universe and has begun to provide a basis on which to distinguish between competing cosmological models. There has been a 30‐year effort, now drawing to a close, to get precise measurements of two parameters that will provide a crucial test for cosmological models. The two key numbers are the rate of expansion (the Hubble constant H0) and the deceleration in the expansion (q0). The hope is that current research, by determining the extragalactic distance scale for nearby galaxies and searching for exceedingly distant clusters where the redshift is large, will measure both of these numbers to a precision of 15%.

100 citations


Journal ArticleDOI
TL;DR: In this article, Sunyaev and Zeldovich give an upper bound on the energy balance of hot plasma and distortions of the spectrum of relic radiation due to dissipation of density fluctuations of matter.
Abstract: Fluctuations of all scales are equally interesting from the point of view of the characteristics of the singular state and not only those which led to the formation of astronomical objects such as clusters of galaxies, separate galaxies, globular clusters and quasars. In this article estimates are given of the homogeneity of the overall density of hot plasma and the relation between the quantity of baryons and antibaryons at early stages of evolution of the Universe. These estimates are made for small scales, considerably smaller than the scale of the astronomical objects enumerated above. Considerations about the energy balance of hot plasma and distortions of the spectrum of relic radiation due to dissipation of density fluctuations of matter are used for these estimates. The corrected upper limit to early energy injection is given. In our preceding paper (Sunyaev and Zeldovich, 1970) this upper limit was underestimated. Difficulties with a model of the Universe which is symmetric in baryon charge are noted.

84 citations



01 Jan 1970

71 citations


Journal ArticleDOI
TL;DR: In this paper, the application of geometric optics to the study of observational properties of cosmological models examined in a previous paper is discussed, and a number of results concerning these properties are derived, the most interesting of which is the invariance of observational relations under certain discrete isotropy groups.
Abstract: This paper discusses the application of geometric optics to the study of observational properties of cosmological models examined in a previous paper. A number of results concerning these properties are derived, the most interesting of which is the invariance of observational relations under certain discrete isotropy groups. Closed form expressions are obtained in certain cases.

65 citations


Journal ArticleDOI
Joseph Silk1
TL;DR: The ability of various theories to explain the three main spectral features at 1/4 keV, 60 keV and 1 MeV is summarized in Tables II and III as mentioned in this paper.
Abstract: The ability of the various theories to explain the three main spectral features at 1/4 keV, 60 keV and 1 MeV is summarized in Tables II and III. Clearly, confirmation of the reality of these features, especially the soft X-ray and γ-ray excesses, is one of the key elements in enabling us to decide between the competing theoretical interpretations. None of the proposed interpretations are easily explained in terms of the available energy in cosmic rays (except perhaps the Seyfert galaxy proposal, and this runs into difficulties). It seems that one either has to regard normal galaxies at the present epoch as prolific sources of cosmic rays (∼ 1060 erg/galaxy in protons), as is required by the Brecher-Morrison model, or to argue that at early stages in their evolution far more energy is available than at present. One ends up with much the same energy requirement in this approach. One could conceivably identify such an early phase with the radio galaxy or QSO phenomena: in any event, cosmological evolution plays a major role. Cosmology does ease the energy requirements, but only for the inefficient mechanisms, such as nonthermal bremsstrahlung or π° -production. It seems that one still needs the metagalactic cosmic ray flux to be ∼ 10-2 of the galactic flux in the diffuse inverse Compton models, and 10-2–10-4 in the nonthermal bremsstrahlung models. Faced with problems of energetics, one is tempted to turn to the most energetic objects in the Universe, namely Seyfert nuclei and QSO's, to provide the basic energy source, whether directly or indirectly, for the diffuse X-ray background. A direct connection could be more readily investigated when X-ray observations are available of more extra-galactic sources. Another approach, complementary to that of looking for remote discrete sources, is to seek angular fluctuations, or limits on such fluctuations in the diffuse X-ray background. The best results presently available are those from the X-ray experiment on board OSO 3. Schwartz (1970) reports a limit of δI/I∼four percent on small-scale (∼10°) fluctuations over 10–100 keV over about one-quarter of the sky. If one assumes a astrophysics, namely the origin of cosmic rays, is intimately linked to the origin of the X-ray background. It may well be that no single mechanism suffices to account for the entire spectrum of isotropic X- and γ-radiation. Nature is sufficiently perverse for there to be a reasonable probability that several different processes are contributing, and considerable ingenuity will be required to ascertain which mechanism, if any, is assigned the dominant role in a given spectral region.






Journal ArticleDOI
TL;DR: Shear and rotation limits on universe from X ray background, using Euclidean shear and vorticity models with open and closed geometries as mentioned in this paper, were derived from the X-ray background.
Abstract: Shear and rotation limits on universe from X ray background, using Euclidean shear and vorticity models with open and closed geometries




Journal ArticleDOI
TL;DR: In this paper, it was shown that if no heating source of matter exists, the matter temperature Tm downs faster than the radiation temperature Tr after the epoch of the decoupling at Tr::::::4000°K.
Abstract: The growth of primordial density contrasts and their separation from the general expansion of the universe are the first step in the course of galaxy formation, which has been attempted to describe by various mechanisms. The epoch of the separation depends on the amount of density contrasts at some epoch, which must be more than several billion years ago. In the case of ~ravitational instability there arises some lower limit for the initial density contrast which cannot be explained by the statistical origin.> It has been expected, on the other hand, that thermal instability may play an important role at an early stage of the growing of the density contrasts.),S) This mechanism can be effective, only if heating and cooling balance each other so as to keep matter at high temperature (at least higher than 10 °K) at the pregalactic stage. However, if no heating source of matter exists, the matter temperature Tm downs faster than the radiation temperature Tr after the epoch of the decoupling at Tr::::::4000°K. > The rotational and peculiar motions of the galaxies in the present state suggest us a possibility that enormous turbulent motions have existed at the pregalactic stage. Weizsacker> and Gamow> insisted upon its importance in the problem of galaxy formation. To meet with this, the theory of turbulence in the expanding universe has been developed by one of the authors (H. N.).>•*> On the basis of a more realistic picture for the hot universe motivated by the discovery of cosmic black-body radiation, Ozernoi and Chernin> have recently


Journal ArticleDOI
25 Jul 1970-Nature
TL;DR: An examination of the flux S and redshift z of radio galaxies in the third Cambridge catalogue lends some encouragement to the steady state cosmology.
Abstract: An examination of the flux S and redshift z of radio galaxies in the third Cambridge catalogue lends some encouragement to the steady state cosmology.

Journal ArticleDOI
02 May 1970-Nature
TL;DR: Hydrodynamical aspects of the evolution of the cosmic fluid at the matter-dominated stage are considered, assuming cosmological expansion to be described by an open Friedmann model because of a number of observational and theoretical arguments.
Abstract: THE development of von Weizsacker's cosmogonical hypothesis1 has led to work2 on the combined hydrodynamical motions of the photon gas and the cosmic plasma in the early hot universe, when the radiation density ρr greatly exceeds the density of matter ρ. In the case of vortex motions, the initial stage of cosmological expansion is non-Friedmannian with anisotropic and inhomogeneous geometry2. But there is some speculation in favour of the motion having a potential character, and in this case the departures from the Friedmann model are small at all epochs, from the general theory3. Here I consider hydrodynamical aspects of the evolution of the cosmic fluid at the matter-dominated stage, assuming cosmological expansion to be described by an open Friedmann model because of a number of observational and theoretical arguments4–6.


Journal Article
TL;DR: Shear and rotation limits on universe from X ray background, using Euclidean shear and vorticity models with open and closed geometries as mentioned in this paper, were derived from the X-ray background.
Abstract: Shear and rotation limits on universe from X ray background, using Euclidean shear and vorticity models with open and closed geometries


Journal ArticleDOI
01 Jan 1970-Nature
TL;DR: In this paper, the authors proposed a model of a uniformly expanding universe in terms of a family of mutually receding galaxies and associated fundamental observers, where the distance between any pair of fundamental observers is related to their mutual recession velocity, w, and their measure of cosmic time, t, by the Hubble law where r and w are the estimates of these quantities by each fundamental observer from his light-intensity and Doppler redshift measurements, and where the present value of t is given by the reciprocal of the Hubble constant.
Abstract: I HAVE already described1,2 a model of a uniformly expanding universe in terms of a family of mutually receding galaxies and associated fundamental observers. It was assumed that the distance, r(t), between any pair of fundamental observers is related to their mutual recession velocity, w, and their measure of cosmic time, t, by the Hubble law where r and w are the estimates of these quantities by each fundamental observer from his light-intensity and Doppler redshift measurements, and where the present value of t is given by the reciprocal of the Hubble constant. I further assumed following McCrea3 that this system of mutually receding galaxies (the fundamental particles of our model) defines a basic reference frame or substratum for the propagation of light and indeed of all forms of energy.

Journal ArticleDOI
TL;DR: Galactic evolution, reviewing Hubble theory of distances and red shift, Friedman model of expanding universe, big bang model, etc as mentioned in this paper, etc. And the Friedman model can be viewed as the basis for the Big Bang model.
Abstract: Galactic evolution, reviewing Hubble theory of distances and red shift, Friedman model of expanding universe, big bang model, etc

Journal ArticleDOI
TL;DR: In this paper, basic equations for dealing with various non-linear effects of cosmic fluid, such as the interaction between eddy motions and shearing ones and the nonlinear character of gravity for the promotion of density contrast, are derived from our Newtonian hydrodynamical equations in an expanding universe, which are suitable after the decoupling time of matter from the primordial radiation.
Abstract: In order to clarify the process of galaxy formation, basic equations for dealing with various non-linear effects of cosmic fluid, such as the interaction between eddy motions and shearing ones and the non-linear character of gravity for the promotion of density contrast, are derived from our Newtonian hydrodynamical equations in an expanding universe, which are suitable after the decoupling time of matter from the primordial radiation. The equations are localized by means of power series expansion of relevant quantities in the neighborhood of an equilibrium point in the fluid and solved in several cases. As a result, it is shown that, if a suitable rotation specified by a parameter e such as 1>e20 exists, the rotating body becomes a gravi­ tationally bound system at an instant when the density ratio to the background reaches the value (3n/ 4)2 {2/ (1 +e) }3. Basic equations for dealing with Ozernoi and Chernin's mechanism for hydrodynamical instability before the decoupling time are also derived in a tentative manner.