Showing papers on "Particle horizon published in 1981"
TL;DR: In this paper, the authors proposed a model of hot big-bang cosmology where the early universe is assumed to be highly homogeneous, in spite of the fact that separated regions were causally disconnected (horizon problem).
Abstract: The standard model of hot big-bang cosmology requires initial conditions which are problematic in two ways: (1) The early universe is assumed to be highly homogeneous, in spite of the fact that separated regions were causally disconnected (horizon problem); and (2) the initial value of the Hubble constant must be fine tuned to extraordinary accuracy to produce a universe as flat (i.e., near critical mass density) as the one we see today (flatness problem). These problems would disappear if, in its early history, the universe supercooled to temperatures 28 or more orders of magnitude below the critical temperature for some phase transition. A huge expansion factor would then result from a period of exponential growth, and the entropy of the universe would be multiplied by a huge factor when the latent heat is released. Such a scenario is completely natural in the context of grand unified models of elementary-particle interactions. In such models, the supercooling is also relevant to the problem of monopole suppression. Unfortunately, the scenario seems to lead to some unacceptable consequences, so modifications must be sought.
8,758 citations
Journal Article•
TL;DR: In this paper, it was shown that over a finite time, quantum fluctuations of the curvature disrupt the nonsingular cosmological solution corresponding to a universe with a polarized vacuum.
Abstract: Over a finite time, quantum fluctuations of the curvature disrupt the nonsingular cosmological solution corresponding to a universe with a polarized vacuum. If this solution held as an intermediate stage in the evolution of the universe, then the spectrum of produced fluctuations could have led to the formation of galaxies and galactic clusters.
1,681 citations
TL;DR: In this paper, a model of the early universe in which domains are stretched exponentially and the radius of the domains is much greater than that of the horizon of the standard big bang model was proposed.
294 citations
Book•
01 Jan 1981TL;DR: Cosmology: The Science of the Universe as discussed by the authors is an introduction to past and present cosmological theory and provides a comprehensive survey of man's current understanding of the universe and its history.
Abstract: Cosmology: The Science of the Universe is an introduction to past and present cosmological theory. For much of the world's history, cosmological thought was formulated in religious or philosophical language and was thus theological or metaphysical in nature. However, cosmological speculation and theory has now become a science in which the empirical discoveries of the astronomer, theoretical physicist, and biologist are woven into intricate models that attempt to account for the universe as a whole. Professor Harrison draws on the discoveries and speculations of these scientists to provide a comprehensive survey of man's current understanding of the universe and its history. Tracing the rise of the scientific method, the major aim of this book is to provide an elementary understanding of the physical universe of modern times. Thoroughly revised and updated, this second edition extends the much acclaimed first edition taking into account the many developments that have occurred.
231 citations
TL;DR: In this article, the implications for magnetic monopole production of a first-order phase transition in the evolution of the early universe are discussed, and the implications of such a phase transition for the generation of a baryon excess are discussed.
51 citations
TL;DR: In this article, the effect of a quantized conformally invariant scalar field in a closed Robertson-Walker universe is studied, and the general solution is characterized by one parameter ξ = Ta which measures the radiation content of the universe.
31 citations
TL;DR: In this paper, the de Sitter-Schwarzschild universe counterpart of the Teukolsky equation was considered with a black hole side on the cosmological horizon and the neutrino transmission coefficient was shown to be zero.
Abstract: The counterpart of the Teukolsky equation in the de Sitter---Schwarzschild universe (i.e., the radial part of the perturbed field equations) for massless fields of spin $s=0, \frac{1}{2}, 1, \mathrm{and} 2$ are considered with waves incident from the black-hole side on the cosmological horizon. In the limiting case of the mass of the black hole being small, we have derived an expression for the reflection coefficient. Here also, as in the de Sitter universe, the neutrino transmission coefficient is found to be zero.
11 citations
TL;DR: The cosmological equations for the general scalar tensor theory proposed by Nordvedt (1970) in a Bianchi type-I radiation-filled universe are solved and the behaviour of the model is discussed in this paper.
Abstract: The cosmological equations for the general scalar tensor theory proposed by Nordvedt (1970) in a Bianchi type-I radiation-filled Universe are solved and the behaviour of the model is discussed. There are two distinct situations. Either the Universe will explode from a bit band type singularity and continuously increase, or the Universe may continuously contract to approach the singularity at the end.
9 citations
TL;DR: In this paper, it was shown that the mass energy of the Friedmann universe relative to an observer in the non-metric space outside the universe is equal to zero, i.e. the universe originated as a vacuum fluctuation.
Abstract: In Section 1 of the paper the energy equation of the Friedmann universe, when matter dominates over radiation, is discussed. It is known that the value of the world potential is constant everywhere in the Universe, despite the pulsation motion of the Universe or a possible transformation of pulsation energy into matter or vice versa. The condition for the Universe being closed is deduced. Furthermore, the possibility to define the mass-energy of the Universe is discussed; and the conclusion is arrived at that the mass-energy of the Universe relative to an observer in the non-metric space outside the Universe is equal to zero; i.e. the Universe originated as a vacuum fluctuation. Finally, the view-point of an external observer is described. Such an observer can claim that our closed Universe is a black hole in a non-metric empty space. Besides, the differences between such a black hole and the astrophysical black holes are indicated.
5 citations
TL;DR: In this paper, the authors present the result of an experiment of the Florence group which has detected a quadrupole anisotropy in the cosmic background radiation and show that this result implies that the universe either has large metric perturbations outside the particle horizon, or will become largely irregular in the future.
Abstract: We present the result of an experiment of the Florence group which has detected a quadrupole anisotropy in the cosmic background radiation. We show that this result implies that the universe either has large metric perturbations outside the particle horizon, or will become largely irregular in the future.
01 May 1981
TL;DR: In this paper, the role of neutrinos in the development of structure in the universe (galaxies, clusters, etc.) is discussed, as well as their role in the evolution of the universe.
Abstract: Neutrinos perhaps best illustrate the close relationship that exists between cosmology and elementary particle physics. Cosmological and astrophysical observations can be used to constrain neutrino properties. The abundance of the 4He probably limits the number of light (<1 MeV) neutrino species to be less than or equal to 4. An unstable neutrino with lifetime α mν−5 is restricted to be less massive than ∠220 eV or more massive than ∠10‐100 MeV. Neutrinos more massive than a few eV have important cosmological consequences: if the sum of neutrino masses ≳3.5 eV the universe is neutrino‐dominated, and if it is ≳100 eV the universe is closed. The role that neutrinos play in the development of structure in the universe (galaxies, clusters, etc.) is also discussed.
TL;DR: In this article, a review of various events in the early universe where nuclear and elementary particle physics effects come into play is made, and some detail is given to new results on big bang nucleosynthesis, massive neutrinos and inflationary scenarios.
01 Sep 1981
TL;DR: In this paper, a scenario is proposed for the evolution of the universe, starting with the quantum birth of a closed world at a minimum in the self-consistent de Sitter cosmological solution with vacuum polarization.
Abstract: A scenario is proposed for the evolution of the universe, starting with the quantum birth of a closed world at a minimum in the self-consistent de Sitter cosmological solution with vacuum polarization. The closure of the universe and the permanently supercritical value of its density follow directly from a single condition: that quantum birth take place. The perturbations must be small in order that the de Sitter phase may be sufficiently prolonged to ensure a protracted Friedmann plasma-matter expansion. Thus a universe having the properties we observe may in fact have been singled out by the anthropogenic principle.
TL;DR: In this paper, the growth of a class of inhomogeneities embedded in a spatially flat Robertson-Walker background is examined, restricted by the simplifying assumption that the isotropic pressure, as measured along the associated boundary surface, equals the local energy flux.
Abstract: The growth of a class of inhomogeneities embedded in a spatially flat Robertson-Walker background is examined. The inhomogeneities are restricted by the simplifying assumption that the isotropic pressure, as measured along the associated boundary surface, equals the local energy flux. The background is described both by means of a noninteracting mixture of blackbody photons and dust, and by means of a baryon-conserving equilibrium mixture of blackbody photons and a neutral, two-component, relativistic Maxwell-Boltzmann gas. We compare the resultant mass of the inhomogeneities with the Jeans and particle horizon mass scales and demonstrate the critical effect that varying the initial photon-to-baryon ratio in the background has on all masses.
01 Jan 1981
TL;DR: The non-microwave data are therefore in agreement with the microwave data in indicating that the universe may be globally inhomogeneous as discussed by the authors, and they give the limit Delta rho/rho less than 0.4 for the global variation of matter density.
Abstract: Recent observations of the quadrupole anisotropy of the 3 K microwave background indicate that the universe may be inhomogeneous on scales larger than the present Hubble radius. Observations of galaxies and QSOs are analyzed to see what non-microwave data indicate about the homogeneity of the universe. They give the limit Delta rho/rho less than 0.4 for the global variation of matter density. This does not satisfy the condition Delta rho/rho much less than 1 for homogeneity. The non-microwave data are therefore in agreement with the microwave data in indicating that the universe may be globally inhomogeneous.
TL;DR: In this article, a two-component model of the universe is proposed, based on the observations of discrete extragalactic sources and the microwave background radiation, and a reasonable agreement with the cosmological tests is obtained on the assumption that the geometry within a typical super-supercluster is Euclidean and that the redshifts of galaxies arise from Doppler effect due to motions originating in a local explosion which gave birth to the super-cluster.
Abstract: A two-component model of the universe is proposed, based on the observations of discrete extragalactic sources and the microwave background radiation. The large scale dynamics of the universe is determined by the radiation component and it leads to a characteristic size of the universe ∼6×105 Mpc and an age ∼1012 yr. The second component, that of matter, occurs in discrete sources which group together in super-superclusters of characteristic size ∼6×103 Mpc and age ∼1010 yr. It is suggested that our Galaxy belongs to one of these super-superclusters and that observations of discrete sources are confined to this unit. A reasonable agreement with the cosmological tests is obtained on the assumption that the geometry within a typical super-supercluster is Euclidean and that the redshifts of galaxies arise from Doppler effect due to motions originating in a local explosion which gave birth to the super-supercluster. Further observational checks on this model are proposed.
TL;DR: In this paper, the effect of neutrinos with non-zero rest-mass on the clustering process in the early universe is discussed. And the main conclusions are: (1) such neutrino will cause clustering of matter before the epoch of re-combination; (2) the mass so clustered will be in the range of the mass of clusters of galaxies; (3) there exists a preferential clustering scale, corresponding to the earliest onset of Jeans instability; (4) if the restmass is below a certain value, then there will be no
TL;DR: In this paper, events in the very early big bang universe in which elementary particle physics effects may have been dominant are discussed, with attention to the generation of a net baryon number by way of grand unification theory, and emphasis on the possible role of massive neutrinos in increasing current understanding of various cosmological properties.
Abstract: Events in the very early big bang universe in which elementary particle physics effects may have been dominant are discussed, with attention to the generation of a net baryon number by way of grand unification theory, and emphasis on the possible role of massive neutrinos in increasing current understanding of various cosmological properties and of the constraints placed on neutrino properties by cosmology. It is noted that when grand unification theories are used to describe very early universe interactions, an initially baryon-symmetrical universe can evolve a net baryon excess of 10 to the -9th to 10 to the -11th per photon, given reasonable parameters. If neutrinos have mass, the bulk of the mass of the universe may be in the form of leptons, implying that the form of matter most familiar to physical science may not be the dominant form of matter in the universe.
TL;DR: In this article, a closed gravitationally-bound universe is assumed to have an inward acceleration of 7.623×10−12 ms−2 and a radiation formula from a previously-described cosmological model.
Abstract: In a closed gravitationally-bound Universe we are subject to an inward accelerationa
0. One consequence of this acceleration is that matter will radiate and create a black-body spectrum throughout the Universe. Using the valuea
0=7.623×10−12 ms−2 and a radiation formula from a previously-described cosmological model (Wahlin, 1981), we obtain a black-body temperature of 2.766 K.
TL;DR: In this paper, it was shown that, in a small region of space-time, it is possible for large fluctuations to develop in both the metric and physical variables describing the universe.
Abstract: Starting from a small perturbation in the initial data for a Robertson-Walker universe, it is shown that, in a small region of space-time, it is possible for large fluctuations to develop in both the metric and physical variables describing the Universe. The initial data are specified on a characteristic hypersurface in a region of perfect fluid filled space-time and the method of analysis of the field equations is based on the techniques introduced by Bondi, van der Burg and Metzner (1962).