Showing papers on "Cosmology published in 1981"

Cosmology and elementary particles

Abstract: The restrictions on elementary particle properties which can be derived from cosmological and astrophysical data are considered. The inverse relations between micro- and macrophysics are also discussed, in particular the origin of the baryon asymmetry of the universe.

Big Bang Nucleosynthesis as a Probe of Cosmology and Particle Physics

Abstract: The mass fraction of 4He synthesized in the big bang, YP, depends upon the neutron half-life T1/2, the ratio of baryons to photons eta, and the number of two-component neutrino species NV. New observational and experimental data have led us to reexamine the constraints on cosmology and particle physics which follow from primordial nucleosynthesis. We find that eta must lie in the range 10-9.9±1, implying that baryons alone cannot close the universe; the related ratio of the baryon number to the specific entropy must lie in the range l0-10.8±1. If baryons provide most of the mass which binds binary and small groups of galaxies, then Nbeta must be V. If the universe is dominated by nonbaryonic matter, than there is no contradiction between the predictions of primordial nucleosynthesis and the observations of 4He, provided that YP 0.15.

The cosmic X-ray background

Abstract: As the sky in the microwave band is dominated by a cosmic background, so too is the X-ray sky. In this report, the experimental approach used for measuring the X-ray background is explained and evaluated. The Compton-Getting interpretation of the dipole anisotropy in the microwave background is presented as a diagnostic of the weak asymmetry exhibited by the cosmic X-ray background. Spectral characteristics and spatial fluctuations of this X-ray background are described and then discussed within the context of what is known about individual extragalactic sources. It is concluded that the bulk of the cosmic X-ray background is yet to be understood. The critical apparatus of modern cosmology is reviewed and applied to this problem, providing constraints and indicating possible avenues for achieving a solution. The outlook for obtaining the new data called for is examined in terms of experiments now in preparation.

Inflation in the Universe

Abstract: During the past 15 yr a small but remarkable collection of cosmological conundrums have been identified; each apparently independent, but probably all inter-related at a deeper level than existing theories have penetrated. The outstanding problems are of explaining the observed isotropy, homogeneity, flatness and specific entropy of the Universe1. Good explanations for the last of these have recently emerged2,3 from the study of C, CP and baryon nonconserving interactions which arise in grand unified gauge theories (GUTs) of the strong and electroweak interactions. Recently, Guth has discussed the inflationary Universe as a possible natural explanation for the observed large-scale homogeneity and near critical density (‘flatness’) of the Universal expansion4. We show that one cannot ignore the first conundrum—the isotropy; a Universe with a large amount of anisotropy will not undergo the inflationary phase. A Universe with only moderate anistropy will undergo inflation and will be rapidly isotropized. Other consequences of the inflationary Universe are discussed.

Is the Gravitational Constant Changing

Abstract: The question posed by the title is not yet conclusively resolved. Nonetheless, determinations of the lunar tidal acceleration based on dynamical time scales are now in reasonable accord with one another, whether based on the transits of Mercury, ancient eclipse observations, ocean tide models, or artificial satellite observations; these give a purely tidal component of −28.8 ± 1.5 ″/cy2. Lunar occultations and laser ranging now give concordant results for the total anomalous acceleration of about −22.8 ± 1.5. The difference in these results gives an acceleration of possible cosmological origin of \( \dot n/n = + 3.5 \pm 1.2 \times 10^{ - 11} \) per year, which is also consistent with very preliminary planetary radar studies. If interpreted in the scalar covariant cosmology of Canuto and Hsieh, this implies that Ġ/G = (−6.9 ± 2.4) × 10−11 per year, if measured in atomic time, but zero if measured in dynamical time. The implications for relativity and cosmology are discussed briefly in the paper, scheduled for the Astrophysical Journal issue of 1 September 1981.

The growth of anisotropic structures in a Friedmann universe

Abstract: Motivated by observational evidence for the existence of flattened or striated structures of very large scale (approx.100 Mpc) in the universe, we study the evolution of nonspherical structures. We set up equations to describe the evolution of a rotating, dust ellipsoid in an expanding universe. We derive solutions for the shape and density evolutions as the ellipsoid expands along with a Friedmann background universe and show that deviations from spherical symmetry are preserved by adiabatic expansion. Analytic expressions are derived to describe the nonlinear evolution of pressure-free ellipsoids. We calculate details of ''pancake'' formation which are relevant for realistic theories of galaxy and cluster formation. In particular, the density collapse at turnaround and the collapse velocity at pancake formation are found to be reduced relative to the spherical case if the initial fluctuations are anisotropic: this may affect kinematic determinations of ..cap omega.. in the local supercluster and also enable galaxies with massive halos to form during the fragmentation of pancakes whose dynamics are dominated by massive neutrinos. Significant deviations from spherical symmetry in the baryon irregularity spectrum might also be naturally associated with primordial isothermal inhomogeneities in a Friedmann universe and their possible origin at the epoch of ''grandmore » unification.'' An exact model for a general relativistic pancake collapse is given, based on an exact solution to Einstein's equations found by Szekeres. This collapse does not pass through a series of ellipsoids and has no symmetries.« less

Toward the application of metric size function in galactic evolution and cosmology

Abstract: We have measured the metric size function eta(r) defined by Petrosian on a limited sample of luminous distant galaxies, up to a redshift of 1.175. Although our investigation has a preliminary character, we find some evidence for the evolution of elliptical galaxies. Using the Ostriker-Hausman theoretical models, we place some constraints on the rates of dynamical evolution.

Evolution of small perturbations of isotropic cosmological models with one-loop quantum gravitational corrections

Abstract: Equations have been derived for small perturbations of homogeneous isotropic cosmological models, which take into account in the one-loop approximation the quantum gravitational effects produced as a result of interaction of the quantum fields of matter with the self-consistent gravitational field.

Gravitational clumping and the annihilation of monopoles

Abstract: It is shown that within the standard model of the early universe no consistent scenario can be constructed for sufficient annihilation of monopole-antimonopole pairs due to gravitational clumping. This result implies that the resolution of the problem of too many primordial monopoles must be a mechanism to suppress their initial creation.

The influence of cosmological gravitational waves on a Newtonian binary system

Abstract: The interaction of a continuous gravitational wave with a Newtonian binary system is discussed, and the possibility of using the orbital perturbations to detect cosmological gravitational waves is investigated The response of the binary system is dominated at late times by secular terms that appear in the orbital perturbations The dominant secular terms are calculated, and it is shown that they can be used to put interesting upper limits on the energy density of cosmological gravitational waves In particular, the recent studies of the Earth-Moon and Earth-Mars distances tentatively limit the energy density of the waves, in units of the closure density, to be less than 10 and 005 for incoherent waves with periods of 1 month and 1 year, respectively The possibility of existence of cosmological waves with these periods is discussed

Grand unification and possible matter-antimatter domain structure in the Universe

Abstract: The theory and basic concepts for the development of a matter-antimatter domain cosmology are outlined within the framework of the grand unified gauge theory paradigm. It is shown how spontaneous CP symmetry breaking leads to such a domain sturcture in the universe. Astrophysical data such as the cosmic gamma-ray background spectrum, cosmic-ray p flux measurements, and galaxy clustering are found to favor this point of view. Future tests of this form of big-bang cosmology are suggested and discussed, including tests using deep underwater cosmic ray neutrino detectors.

Evolution of perturbations in Friedmann models of the Universe

Abstract: Equations describing the evolution of perturbations of arbitrary magnitude are obtained in the framework of Friedmann cosmological models. It is assumed that the scale of the perturbations is many times less than the distance to the horizon and that the amplitude never attains relativistic values, so that gravitation can be described in the Newtonian approximation. An important feature of the obtained equations is the fact that they are independent of the Hubble constant and ratio of contemporary matter density to that required to close the universe of the cosmological model. Thus, the question of similarity of evolution of perturbations in models with different critical density ratios is solved. The perturbations evolve in three different regimes depending on the type of cosmological model (open, critical, or closed), so that the behavior of the perturbations is similar only within one type of model. However, the transition to a model with a definite critical density ratio for a fixed type of cosmological model is achieved simply by a scale transformation.

The possibly massive symbiotic system V 1329 Cygni

Abstract: A new radial velocity curve of V 1329 Cyg has been obtained from emission lines originating around an evolved star. The latter might be faced by an M-type mate, whose mass is larger than 23±6 solar masses. The system seems at |Z|>250 pc from the galactic plane. The λ6830 unidentified band, found in V 1329 Cyg and among BQ [ ] stars, symbiotic stars and a few planetary nebulae, could be used as a diagnostic tool to identify very evolved stars. The close similarity of the optical spectrum of V 1329 Cyg to that of the optical counterpart of GX 1+4 is remarkable.

Demise of the Lemaître cosmological models and objects at large redshift

Abstract: Recent uniform samples of QSO Lyα absorption lines make possible new cosmological tests out to large redshifts and the detection of superclustering out to redshift z~3. One test involves the Lemaitre models of the Universe, which predict large peaks in the number of objects per unit redshift, near the redshift of their characteristic quasistatic period. No such peaks are seen in the Lyα cloud distribution.

Texas Symposium on Relativistic Astrophysics, 10th, Baltimore, MD, December 15-19, 1980, Proceedings

Abstract: The present conference on relativistic astrophysics begins with consideration of such topics in the cosmology of the early universe as the implications of the neutrino rest mass, relic neutrino clustering, and the possibility of a matter-antimatter domain structure in the universe, and proceeds to the broader cosmological questions of the distances of extragalactic objects, the mass of the universe, and the dynamics of superclusters. Also considered are the cosmic microwave background, relativistic jet production and propagation in active galaxies, gravitational lenses, positron annihilation radiation from the galactic center region, supernova models, and the acceleration of cosmic rays by shock waves. Summaries are presented in closing, on workshops concerning such topics as gravitational radiation detectors, the UV cosmic ray background, pulsars, supernovae, active galaxies, and quasars.

Improved standard cosmology

Abstract: An exact solution of Einstein's equations is given. It represents spherically symmetric clusters of galaxies, with inhomogeneous inverse-square density profiles, embedded in a homogeneous Einstein--de Sitter universe. This model represents an improved standard cosmology, in that it is in better agreement with the observation that most galaxies are in clusters than is the purely homogeneous Einstein--de Sitter model. The new model agrees with a recent reformulation of the cosmological principle.