Showing papers on "Cosmology published in 1976"
01 Jan 1976
TL;DR: Ohanian and Ruffini's Gravitation and Spacetime, Second Edition, the authors is the best book on the market today of 500 pages or less on gravitation and general relativity.
Abstract: Now more than ever, Gravitation and Spacetime, Second Edition, by Hans C. Ohanian and new coauthor Remo Ruffini, deserves John Wheeler's praise as "the best book on the market today of 500 pages or less on gravitation and general relativity." Gravitation and Spacetime has been thoroughly updated with the most exciting finds and hottest theoretical topics in general relativity and cosmology. Highlights of the revision include the rise and fall of the fifth force, principles and applications of gravitational lensing, COBE's spectacular confirmation of the blackbody spectrum of the cosmic thermal radiation, theories of dark matter and inflation, and the early universe as a testing ground for particle physicists' unification theories, and much, much more. The ideal choice for a graduate-level introduction to general relativity, Gravitation and Spacetime is also suitable for an advanced undergaduate course.
547 citations
TL;DR: In this paper, a general procedure for transforming asymptotically flat axially symmetric solutions of the Einstein-Maxwell equations into solutions resembling Melvin's magnetic universe is presented.
Abstract: We present a general procedure for transforming asymptotically flat axially symmetric solutions of the Einstein–Maxwell equations into solutions resembling Melvin’s magnetic universe. Specific applications yield metrics associated with black holes in a magnetic universe. It is hoped that these solutions will be of interest to astrophysicists studying gravitational collapse in the presence of strong magnetic fields.
254 citations
154 citations
TL;DR: In this article, a model of giant elliptical primeval galaxies (PGs) based on Larson's models indicate that their most luminous phase occurs when their nuclei are formed, and that such objects should appear as faint stellar or fuzzy stellar objects with possible emission lines and a wide range of colors dependent on their redshifts.
Abstract: Models of giant elliptical primeval galaxies (PGs) based on Larson's models indicate that their most luminous phase occurs when their nuclei are formed. Such objects should appear as faint stellar or fuzzy stellar objects with possible emission lines and a wide range of colors dependent on their redshifts. If most gE PGs had a mass around that of the models (10/sup 11/ M/sub sun/), they would be only barely detectable in a closed cosmology (m/sub R/approximately-greater-than21) and invisible in an open one, since most would have formed at high redshifts. However, more massive PGs or ones formed at zapproximately-less-than5 could be detected photometrically. Condensed PGs, masquerading as stellar images, would have escaped notice in the unsuccessful searches for extended PGs by Patridge and Davis and Wilkinson. (AIP)
76 citations
73 citations
Journal Article•
68 citations
62 citations
TL;DR: In this paper, it was shown that the expansion of the universe can create particles with a black-body distribution, even before classical thermalising processes have had a chance to act.
Abstract: I show here that the expansion of the Universe can create particles with a black-body distribution. I give a simple model in which the creation of particles in an initially empty space time leads at very early times to a Friedmann expansion dominated by hot relativistic particles (probably including gravitons) having a black-body spectrum, even before classical thermalising processes have had a chance to act. If the particle creation occurs near the Planck time, the entropy produced is consistent, in order of magnitude, with that required by the Einstein equations. The conditions in which one achieves consistency with the observed 3K black-body radiation are also discussed.
59 citations
TL;DR: In this paper, it is shown that in a universe of indeterminate density, the third time derivative of the scaling variable is of greater fundamental importance than the deceleration term.
Abstract: IT is often said that the determination of the deceleration term is one of the main aims of observational cosmology. In the following comments this view is questioned, and in a universe of indeterminate density, the third time derivative of the scaling variable is shown to be of greater fundamental importance.
57 citations
TL;DR: In this article, the authors reviewed the known cosmological solutions of the ECSK field equations and explained the prevention of singularities by means of the extension of the Hawking-Penrose singularity theorems to the EDSK theory.
42 citations
TL;DR: The transition temperature of the hadronic superfluid during the hadron era is estimated to be 10 − 13 K, which is the same as the Hagedorn temperature, giving a physical basis of the thermodynamic bootstrap model as mentioned in this paper.
Abstract: Some cosmological consequences of the superfluid vacuum state developed previously by the authors are discussed, particularly with regard to the initial stages of the universe. The transition temperature of the hadronic superfluid (superfluid during the hadron era) is estimated to be 10
13
K, which is the same as the Hagedorn temperature, giving a physical basis of the thermodynamic bootstrap model.
TL;DR: In this article, it was shown that a primordial tachyon in the big-bang universe cannot survive unless it had very large energy initially, and this time barrier is found to exist even in the quantum-mechanical discussion of tachyons.
Abstract: The propagation of tachyons in an expanding universe is discussed. It is shown that a primordial tachyon in the big-bang universe cannot survive unless it had very large energy initially. In an indefinitely expanding universe, the tachyon trajectory turns back in time. This time barrier is found to exist even in the quantum-mechanical discussion of tachyons. This property is used to set limits on the mass of a tachyon. The possible astronomical checks on the hypothesis that neutrinos or photons may be tachyonic are also discussed.
TL;DR: The post-Newtonian limit of Rosen's theory of gravity is evaluated and is shown to be identical to that of general relativity, except for the post Newtonian parameter alpha sub 2 (which is related to the difference in propagation speeds for gravitational and electromagnetic waves).
Abstract: The post-Newtonian limit of Rosen's theory of gravity is evaluated and is shown to be identical to that of general relativity, except for the post-Newtonian parameter alpha sub 2 (which is related to the difference in propagation speeds for gravitational and electromagnetic waves). Both the value of alpha sub 2 and the value of the Newtonian gravitational constant depend on the present cosmological structure of the Universe. If the cosmological structure has a specific (but presumably special) form, the Newtonian gravitational constant assumes its current value, alpha sub 2 is zero, the post-Newtonian limit of Rosen's theory is identical to that of general relativity - and standard solar system experiments cannot distinguish between the two theories.
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TL;DR: The following example in classical mechanics yields the key equations of relativistic cosmology, including the new equations by Harrison as discussed by the authors, and the argument given here develops that of an earlier note.
Abstract: THE following example in classical mechanics yields the key equations of relativistic cosmology, including the new equations by Harrison1. The argument given here develops that of an earlier note2.
TL;DR: In this paper, the authors show that the RFR data, often taken as evidence for large scale anisotropic cosmic expansion, probably only reflect the inhomogeneous distribution of galaxies in the region of the Rubin-Ford sample.
Abstract: We show that the Rubin–Ford (RFR) data, often taken as evidence for large scale anisotropic cosmic expansion, probably only reflect the inhomogeneous distribution of galaxies in the region of the Rubin–Ford sample. The data RFR have presented are consistent with isotropic expansion, an unperturbed galaxy velocity field and hence a low density Universe.
TL;DR: In this paper, the effect of frictional accretion on the luminosity observed within a given aperture depends on the structures of the galaxies involved and the size of the effect not only depends sensitively on the galaxy structures but is also amplified when the relatively recent collapse times of the clusters are taken into account.
Abstract: Effects on the Hubble diagram of the frictional accretion of small cluster galaxies by large ones, to which Ostriker and Tremaine have recently drawn attention, must be accurately determined if the magnitude-redshift relation is to become a viable cosmological test. We find that the process might be detectable through the concomitant change in galaxy colors, but that its effect on the dispersion of magnitudes of first-ranked cluster galaxies would be negligible even if the change in average magnitude is very important. The sign of the effect of accretion on the luminosity observed within a given aperture depends on the structures of the galaxies involved. The size of the effect not only depends sensitively on the galaxy structures, but is also amplified when the relatively recent collapse times of the clusters are taken into account. It is vital to answer the complicated observational and theoretical questions raised by these preliminary calculations, because the Hubble diagram remains the most promising approach to the deceleration parameter q/sub 0/. Local tests of the density of the universe do not give equivalent information. (AIP)
TL;DR: The number of dris& cult groups at any given point in time has not, as far as I know, been ascertained, except in the case of certain towns and cities as discussed by the authors.
Abstract: YORUBA Orish cults have been receiving attention for a long time now, both singly, and together in more general treatments of Yoruba religion. 2 But many questions remain. For example: census figures may give an approximate number of non-Christians and non-Muslims in Western Nigeria, 3 but the number of dris& cult-groups at any given point in time has never, as far as I know, been ascertained, except in the case of certain towns and cities. 4
TL;DR: In this article, the cosmological interpretation of the red shift in the spectra of quasars leads to yet another paradoxical result: namely, the Earth is the center of the universe.
Abstract: It is shown that the cosmological interpretation of the red shift in the spectra of quasars leads to yet another paradoxical result: namely, that the Earth is the center of the Universe. Consequences of this result are examined.
TL;DR: The main conclusions of as discussed by the authors are that the primeval turbulence theory is not compatible with observations in a low-density universe and that it cannot account for the large angular velocity of the Local Supercluster claimed by de Vaucouleurs.
Abstract: The main conclusions are that the primeval turbulence theory is not compatible with observations in a low-density universe and that it cannot account for the large angular velocity of the Local Supercluster claimed by de Vaucouleurs. (AIP)
TL;DR: The negative mass region of spacetime has local properties similar to those of the negative-mass Schwarzschild solution as discussed by the authors, and as such may be attractive as ''lagging core'' models of highly energetic astrophysical phenomena.
Abstract: Examples are given of spherically symmetric cosmological models containing space-sections with the following properties: at large values of the geometrically defined coordinate R, the mass is positive, while at small values of R, the mass is negative. The negative-mass region of spacetime has local properties similar to those of the negative-mass Schwarzschild solution. The big bang in these models is partially spacelike and partially timelike, so the spacetimes do not obey the strong form of the cosmic censorship hypothesis. The timelike, negative-mass segments of the big bang are unlimited sources of electromagnetic and gravitational radiation, and as such may be attractive as ''lagging core'' models of highly energetic astrophysical phenomena. (AIP)
Journal Article•
TL;DR: The derivation of the redshift (z)-distance (r) relation in the chronometric theory of the Cosmos is amplified and this deviation and the (quantum) dispersion in redshift are shown to be unobservably small.
Abstract: The derivation of the redshift (z)-distance (r) relation in the chronometric theory of the Cosmos is amplified. The basic physical quantities are represented by precisely defined self-adjoint operators in global Hilbert spaces. Computations yielding explicit bounds for the deviation of the theoretical prediction from the relation z = tan2(r/2R) (where R denotes the radius of the universe), earlier derived employing less formal procedures, are carried out for: (a) a cut-off plane wave in two dimensions; (b) a scalar spherical wave in four dimensions; (c) the same as (b) with appropriate incorporation of the photon spin. Both this deviation and the (quantum) dispersion in redshift are shown to be unobservably small. A parallel classical treatment is possible and leads to similar results.
01 Jan 1976
TL;DR: In this article, it was pointed out that these changes are not likely to be confined to the region where the measurements have been made and that the plasmas in regions which are remote in space or in time have basically the same properties as in the present magnetospheres.
Abstract: In the preceding chapters we have seen how drastically in situ measurements in space have changed our views of the properties of cosmic plasmas. It has also been pointed out that these changes are not likely to be confined to the region where the measurements have been made. A plasma has basically the same properties in the magnetospheres as in the laboratory, and it is also likely that the plasmas in regions which are remote in space or in time have basically the same properties as in the present magnetospheres. Hence the conditions at earlier epochs should be treated as extrapolations of the present-day conditions in the magnetospheres (including the heliosphere) and in the upper ionospheres.
TL;DR: In this article, an attempt has been made to observe whether old photons have the same relation between wavelength and energy as young photons, using quasars with redshift up to z = 1.6 as sources.
Abstract: An attempt has been made to observe whether old photons have the same relation between wavelength and energy as young photons. No detectable difference was found, using quasars with redshift up to z=1.6 as sources. Assuming that the speed of light is cosmologically constant, the observations give an upper limit for a hypothetical variation of Planck's constant h of less than 1 part in 10/sup 12/ per year in a reasonable cosmological model. (AIP)
TL;DR: In this article, the effect of absorption by the intergalactic medium in general, and of the above type in particular, on the measurement of the deceleration parameter q 0 of the expanding universe is discussed.
Abstract: In a recent attempt to explain the cosmic microwave background without the big bang, a thermalization mechanism involving intergalactic whisker grains of graphite was proposed. The effect of absorption by the intergalactic medium in general, and of the above type in particular, on the measurement of the deceleration parameterq
0 of the expanding universe is discussed. Its effect is shown to be comparable in magnitude but opposite to that of the luminosity evolution in galaxies. A consequential selection effect is also discussed.
Journal Article•
TL;DR: In this paper, it was shown that the observed approximate equalities are not accidental but causal, and that this leads to an unacceptable past temperature for the Earth, in which case, matter is continuously created such that ρ 0 √ t2 where t is the age of the universe.
Abstract: DIRAC1,2 has modified his earlier cosmological model based on the large number hypothesis3,4, that the observed approximate equalities are not accidental but causal—even though we are as yet unaware of the nature of the relationship between cosmology and local physics (e is the electronic charge, G the gravitational constant, c the velocity of light, ρ the mean density of the Universe, H Hubble's constant and m an atomic mass). In the earlier version, Dirac assumed mass conservation and that equalities (1) held for all time, thus where R(t) is the cosmological scale factor, H = R/R. In the modified version, Dirac argues (unconvincingly in my view) that R(t) ∝ t, in which case that is, matter is continuously created such that ρ0 ∝ t2 where t is the age of the Universe. This newly created matter could be produced uniformly throughout space, or locally in proportion to the amount and composition of matter already present. Dirac prefers the second alternative, but we shall show that this leads to an unacceptable past temperature for the Earth.