Showing papers on "Cosmology published in 1980"

The large-scale structure of the universe

Abstract: Opinions on the large-scale structure of the early universe range widely from primeval chaos to a well-ordered mass distribution. P.J.E. Peebles argues that the evolution proceeded from a nearly uniform initial state to a progressively more irregular and clumpy universe. The discussion centers on the largest known structures, the clusters of galaxies, the empirical evidence of the nature of the clustering, and the theories of how the clustering evolves in an expanding universe. In Chapter One the author provides an historical introduction to the subject. Chapter Two contains a survey of methods used to deal with the Newtonian approximation to the theory of the evolution of the mass distribution. Recent progress in the use of statistical measures of the clustering is described in Chapter Three. Chapters Four and Five return to techniques for dealing with cosmic evolution, in the statistical measures of clustering and under general relativity theory. Lastly, in Chapter Six Professor Peebles assesses the progress in attempts to link theory and observation to arrive at a well established physical picture of the nature and evolution of the universe.

Dynamics of the universe and spontaneous symmetry breaking

Abstract: It is shown that the presence of a phase transition early in the history of the universe, associated with spontaneous symmetry breaking (believed to take place at very high temperatures at which the various fundamental interactions unify), significantly modifies its dynamics and evolution. This is due to the energy 'pumping' during the phase transition from the vacuum to the substance, rather than the gravitating effects of the vacuum. The expansion law of the universe then differs substantially from the relation considered so far for the very early time expansion. In particular it is shown that under certain conditions this expansion law is exponential. It is further argued that under reasonable assumptions for the mass of the associated Higgs boson this expansion stage could last long enough to potentially account for the observed isotropy of the universe.

Where has the fifth dimension gone

Abstract: We show that a simple solution to the vacuum field equations of general relativity in 4 + 1 space-time dimensions leads to a cosmology which at the present epoch has 3 + 1 observable dimensions in which the Einstein-Maxwell equations are obeyed. The large ratio of the electromagnetic to gravitational forces is a consequence of the age of the Universe, in agreement with Dirac's large-number hypothesis.

The Big Bang

Abstract: Readers looking for an introduction to astronomy, specific information on a key astronomical subject, or simply a fascinating story spanning the expanse of time and space will find The Big Bang hard to resist "This is a book that will inspire people to study cosmology" The Observatory Magazine "People with no science background can certainly get a great deal from much of the text, and can appreciate the more thorough treatment of the philosophical and mathematical foundations of the subject" Nature

On the determination of the degree of cosmological Compton distortions and the temperature of the cosmic blackbody radiation

Abstract: We describe a method for a determation of the cosmic blackbody radiation temperature and its degree of cosmological Compton-distortions. Differential measurements at only three frequencies of the additional Compton distortions in a direction to a gas-rich cluster of galaxies are sufficient to determine both of these quantities. The method is essentially independent of the gas properties and, it is argued, can significantly improve on previous determinations of the radiation temperature. The method is implicitly based on the universality of the radiation and thus, if successfully applied, can give strong evidence for the universal nature of the radiation.

Limits to verification in cosmology

Abstract: Consideration is given to the problem of proving observationally that the universe is well described by a Friedmann-Robertson-Walker (FRW) universe model as an example of limits to be encountered in observational verifications in cosmology. The information obtainable from electromagnetic radiation originating from distant galaxies concerning the local space-time geometry is examined in detail, and the ideal observational data that will imply the universe to be a FRW universe model are indicated. Physical limitations preventing the direct observation of this cosmological data are then pointed out, and methods for verifying by observation that a previously determined isotropic cosmological model corresponds to a specific FRW space-time are considered, with attention given to observational limitations, astrophysical uncertainty and selection effects in confirming isotropy verifying spatial homogeneity and determining the Hubble constant and the deceleration parameter. It is concluded that practical limits to verification should be accorded a fundamental status in views of cosmology, since they limit the extent to which cosmology can be considered an observationally based subject.

Are grand unified theories compatible with standard cosmology

Abstract: The existence of superheavy monopoles is a necessary consequence of grand unified field theories. Estimates of the number of monopoles produced in the early Universe are made under some very general assumptions. Except possibly for the case of small Higgs mass, the number produced is many orders of magnitude greater than that allowed by the standard "hot" big-bang cosmology.

Helium Synthesis, Neutrino Flavors, and Cosmological Implications

Abstract: The problem of the production of helium in the big bang is reexamined in the light of several recent astrophysical observations. These data, and theoretical particle-physics considerations, lead to some important inconsistencies in the standard big-bang model and suggest that a more complicated picture is needed. Thus, recent constraints on the number of neutrino flavors, as well as constraints on the mean density (openness) of the universe, need not be valid.

Quantum effects in the early Universe. IV. Nonlocal effects in particle production in anisotropic models

Abstract: The dynamical equation governing the evolution of the effective geometry in the presence of the production of conformally invariant scalar particles is solved for a homogeneous model cosmology with small anisotropy and classical radiation. The pair-production probabilities and spectrum are calculated in the one-loop approximation to lowest nonvanishing order in the deviation from exact isotropy.

Cosmological tests of the Hoyle-Narlikar conformal gravity

Abstract: For the first time the Hoyle-Narlikar theory with creation of matter and a variable gravitational constant G, is subjected to the following cosmological tests: (1) the magnitude versus z relation, (2) the N(m) versus m relation for quasars, (3) the metric angular diameters versus z relation, (4) the isophotal angles versus z relation, (5) the log N-log S radio source count, and finally (6) the 3 K radiation. It is shown that the theory passes all these tests just as well as the standard cosmology, with the additional advantage that the geometry of the universe is uniquely determined, with a curvature parameter equal to zero. It is also interesting to note that the variability of G affects the log N-log S curve in a way similar to the density evolution introduced in standard cosmologies. The agreement with the data is therefore achieved without recourse to an ad hoc density evolution.

Gravitational radiation dominated cosmologies

Abstract: Robertson-Walker cosmologies with matter, radiation, and nonzero cosmological constant are examined to determine how much high-frequency gravitational radiation may be present at the current epoch without violating observations. Evolutionary limits due to a maximum redshift requirement, minimum age requirement, and magnitude-redshift relation are used to rule out most M2 models and to restrict singular models to those satisfying an acceleration parameter limit of -4.4-5.6, a matter density limit of less than 4.7, and a radiation density limit of less than 3.4. These limits are compared to direct limits from various experimental searches for a cosmic gravitational radiation background; it is found that several experiments are very close to a significant sensitivity.

Cosmology, astrophysics and elementary particle physics

Abstract: The Universe provides a laboratory in which it is possible to test the laws of physics in conditions which cannot be achieved in a terrestrial laboratory. The author assumes that the laws of physics are unchanging in space and time and discusses how modern developments in elementary particle physics influence our understanding of the Universe and conversely the possibility that astronomical observations may give information about elementary particle physics. In particular he studies the physics of the early Universe and discusses the role of new particles such as heavy leptons, neutrinos and quarks and the possible relationship of the net baryon number of the Universe to unified models of elementary particle physics. He considers the role of neutrinos in stellar evolution, particularly in the explosion of supernovae and in the cooling of neutron stars. Black holes are also discussed.

The primeval hadron: Origin of stars, galaxies and astronomical universe

Abstract: The relationship between mass and angular momentum for the known cosmic objects has been examined, and it is shown that they are described by the generalized Regge-like dependence of the formJ=(m/mp)1+1/nħ wheren=2 for galaxies, their clusters and superclusters, andn=3 for asteroids, planets and stars. It offers the possibility, that Ambartsumian's superdense proto-matter has hadronic nature. This allows us to give a realistic and quantitave explanation with a minimum number of arbitrary assumptions for the origin of cosmic angular momenta, cosmic magnetic fields and offers the framework for other cosmogonic implications. This approach incorporates in a natural way the fundamental quantum-mechanical parameters ħ andmp, besides the classical parametersG andc, and allows us to derive simple expressions for masses and spins of cosmic objects through fundamental constants, some of which coincide with Eddington-Dirac's ‘Large Number’ relations.

Time dependence of the cosmological redshift in Friedmann universes

Abstract: We generalize a formula of Ebert and Truemper which gives the time dependence of the cosmological redshift for certain special Friedmann universes to all Friedmann universes.

Casimir cancellations in half an Einstein universe

Abstract: The authors 'halve' an Einstein universe in two ways. For the spin-0 field they equatorially bound S3 by S2, while for the spin-1/2 field we factor S3 to give the lens space S3/Z2. In both cases the vacuum expectation value of the stress tensor is identical to that in the complete Einstein universe.

General Relativity and the Eternal Return

Abstract: An arbitrarily close return to a previous initial state of the Universe, such as is predicted by the Poincare recurrence theorem, cannot occur in a closed universe governed by general relativity. The significance of this result for cosmology and thermodynamics is pointed out.

Two soliton waves in anisotropic cosmology.

Abstract: A two-soliton exact solution of the vacuum Einstein equations has been constructed. This solution represents soliton waves propagating on a Bianchi type-I cosmological model. The solution represents one of the possible mechanisms of creation of gravitational waves due to the initial inhomogeneity of the Universe.

The application of dimensional analysis to cosmology

Abstract: Cosmology as it is usually studied suffers from the problem that no criterion is known which isolates from the large class of models allowed by the equations of physics those few which are realized in Nature. To provide such a criterion, it is proposed that cosmology should be based on the study of models which are free of arbitrary scales or units, this condition being compatible with (but not identical with) the Cosmological Principle. Formally, the basis for scale-free cosmology can be expressed in a dimensional Conspiracy Hypothesis: The material parameters of a system (mass, density, pressure etc.), the constants of physics and the coordinates have realizable physical meanings only when they occur together in dimensionless combinations (η-numbers) in which the components may vary with time or place but in such a manner that the variations conspire to keep the η-numbers constant. The Conspiracy Hypothesis (CH) streamlines cosmology, simplifying it to the finding of a few dimensionless numbers. Applied to Einstein's general relativity, the CH yields a simple cosmological model consisting of static clusters of galaxies with inverse-square density profiles embedded in an expanding, homogeneous background. This model agrees well with the observed Universe insofar as the latter can be described by general relativity. The CH can also be applied to other theories of gravity, especially those in which the gravitational parameter G is variable, and can also in itself be taken as a basis for gravitational theory.