Showing papers on "Cosmology published in 1973"

Imperfect fluid Friedmannian cosmology

Abstract: The bulk viscosity is introduced into the frame of ordinary Friedmannian cosmology (under highly idealized assumption of the constant coefficient of bulk viscosity). Explicit solutions are given for the viscous flat universe filled with the dust-substratum and for the viscous radiative universe. The problem, how does the introduction of viscosity affect the appearance of singularity, is briefly discussed.

Extragalactic cosmic rays and the galactic magnetic field

Abstract: The origin and behavior of cosmic rays in the Galaxy depend crucially upon whether the galactic magnetic field has a closed topology, as does the field of earth, or whether a major fraction of the lines of force connect into extragalactic space. This paper examines the structure of a galactic field that opens initially into intergalactic space and, with the inclusion of turbulent diffusion, finds no possibility for maintaining a significant magnetic connection with an extragalactic field. Unless some mechanism can be found, we are forced to the conclusion that the field is closed, that cosmic rays are of galactic origin, and that cosmic rays escape from the Galaxy only by pushing their way out.

Implications of the Statistical Bootstrap Model for Cosmology and Galaxy Formation

Abstract: The statistical bootstrap model suggests that the hadron level density is sigma (m) ~ Cm/sup 3./ exp(m/T/sub h/). With a spectrum of this type, massive hadron resonances will predominate in the early stages of the big bang, and the Universe will evolve out of equilibrium. The decay chains of these resonances may be so lengthy that the hadron era is prolonged far past its conventional end. The subsequent radiation era will be considerably foreshortened with the following major consequences. (i) Large density fluctuations are produced during the hadron era. The foreshortened radiation era is insufficiently lengthy for these fluctuations to be damped out. Thus, unlike conventional models, this model allows the causal development of galaxies from an initially homogeneous and isotropic state. (ii) During the hadron-dominated era a secondary gas of photons, leptons, and baryons builds up from the products of hadron decay. This secondary gas comes into equilibrium allowing the production of the present day 3 deg blackbody radiation despite the foreshortening of the radiation era. The buildup of the secondary gas involves the production of a considerable amount of entropy and thus helps in explaining the presently observed magnitude of the entropy density. (auth)

Dependence of the integrated background light on cosmology, galactic spectra, and galactic evolution

Abstract: The theoretical spectrum and intensity of the integrated light of distant galaxies are studied as a function of uncentain parameters entering their calculation These include the cosmological model, epochs of formation of galaxies, evolution of the magnitudes and colors of galaxies of different types, the ultraviolet radiation of galaxies, and the local luminosity density of the Universe It is found that the background light is affected strongly by all of these factors, in such a way that even highly penetrating observational data could yield little firm information for either cosmology or galactic evolution If better estimates of these parameters than those presently available are obtained from other considerations, measurements of the background light could provide an important test of their consistency (auth)

Observational constraints imposed by Brans-Dicke cosmologies.

Abstract: Flat-space Brans-Dicke (BD) cosmologies previously found are analyzed in more detail. It is shown that the observed values of the matter density, the Hubble age, the ages of objects in the universe, the deceleration parameter, and the bound on the (unobserved) fractional time variation of the gravitational constant are too inaccurate to distinguish between the BD and Einstein-Friedmann cosmologies. An attempt is made to argue that because of the great degree of latitude in the observational constraints imposed by the BD cosmologies, efforts to improve the bound on the fractional time variation of G alone are not sufficient to rule out the BD theory.

Gravitational radiation and observational cosmology

Abstract: Recent observations by Weber indicate that a high flux of gravitational radiation is now being generated within the Galaxy. Assuming our environment to be typical, we must expect all galaxies to behave similarly, leading to large total amounts of gravitational wave energy in the cosmos. We have constructed an evoluational model for the generation of gravitational radiation subsequent to galaxy formation and examined how the dynamics of the Universe are affected by the conversion of matter into radiation over a time scale of several billion years. If our Galaxy now converts more than 100 M/sub sub solar / per year into gravitational waves, we find that this radiation can play as important a role as matter in the evolution of the Universe. We use the latest values of the Hubble constant and deceleration parameter and find that the lifetime of a radiating cosmology is shortened from the Friedmann value to lie in the range 11 to 14 billion years. (auth)

Derivation of the Differential Equation for the Simpler Cosmological Models

Abstract: SEVERAL simplified expositions of cosmology have appeared in the past few years in response to the increased interest in the subject1–7. In these expositions the dimensionless scale factor R(t) at a universal cosmic time t plays an important part. It governs the universal expansion of all linear dimensions of the model and is introduced through the equation illustration where i labels a typical galaxy (or “particle” in the model), ri, is the distance of this galaxy from a galaxy i=0 which acts as origin and t1 is a standard time at which the galaxies are labelled. The differential equation for R is then illustration where Ṙ=dR/dt and B, D and E are constants. The argument, in its Newtonian framework, is based on a homogeneous and isotropic model universe in which the galaxies are assumed to be smeared out to give a mass density p(t) which is constant in space at any one time. Equation (2) is then obtained as an energy equation for a spherical distribution. There then arise some awkward problems concerning the significance of the origin, the significance of the surface of the sphere considered and the effect of the possibly infinite amount of matter outside the sphere. But authors usually manage to make it plausible that none of these effects change equation (2). Open image in new window Open image in new window

Radio Source Depolarization, Size and Cosmology

Abstract: Data on radio source depolarization and the largest angular size against redshift correlation demonstrate the presence of geometrical effects predicted by relativistic cosmology and suggest the existence of significant amounts of inter galactic gas.

Cosmological hadronic fireball

Abstract: Relativistic Non-Zero Pressure Cosmology describes a hadronic fireball in the primordial stage of the Universe near the singularity. It is phenomenologically matched to Hagedorn's equation of state based on thermodynamics of strong interactions.

On redshifts and number counts of extragalactic objects in two cosmological models

Abstract: Observed redshifts and magnitudes of seven classes of extragalactic objects, and number counts of QSRS are compared with predictions made by cosmological models. The uniform model U 1 and the proposed non-expanding model RHL 5 represent the observations very well. The latter offers numerous advantages. Absolute magnitudes and colors are determined.

A stochastic model of the galactic magnetic field

Abstract: Existing stochastic models of the galactic magnetic field are considered and found to suffer certain defects. A new model is proposed which overcomes faults of the previous theories while retaining their strenghts.