Showing papers on "Particle horizon published in 1979"
TL;DR: In this paper, the growth and subsequent collapse of homogeneous ellipsoidal perturbations in a uniform expanding background is considered as a simple model for the formation of large-scale aspherical structures in the observed universe.
Abstract: The growth and subsequent collapse of homogeneous ellipsoidal perturbations in a uniform expanding background is considered as a simple model for the formation of large-scale aspherical structures in the observed universe. Numerical calculations of the evolution of such perturbations turn out to be well described by an approximate analytic solution of the equations of motion, and simple relationships are found between the initial shape of a perturbation and its shape and kinematic properties at the time of collapse. Perturbations do not change their shape significantly until they reach a density contrast of order unity. As a result, structures with the kinematic properties of the Local Supercluster should form much more commonly in a low-density universe than in a flat universe. The homogeneity of the local Hubble flow, the motion of the Milky Way with respect to the microwave background, and the flattening of the Local Supercluster can be successfully accounted for by these models, provided that the initial perturbation is sufficiently flattened. Viable models are obtained only if the ratio of the lengths of the two smaller axes of the initial perturbation is at least 3:1 in an Einstein-de Sitter universe or at least 1.8:1 in a universe for which the density parameter (Omega) is of order 0.1, when the protocluster pancakes.
112 citations
TL;DR: In this article, the model of a homogeneous isotropic universe is studied in the presence of gauge fields, noninteracting dust, and two extra compact dimensions, and it is found that the singular "big bang" type solution can be rejected because of the drastic growth of the radius of the universe.
Abstract: The model of a homogeneous isotropic universe is studied in the presence of gauge fields, noninteracting dust, and two extra compact dimensions. It is found that the singular “big bang” type solution can be rejected because of the drastic growth of the radius of the universe. On the other hand, solutions without singularity can be found showing a very rapid oscillation (Planck frequency) with small amplitude around the data prescribing the present status of the universe.
63 citations
TL;DR: In this paper, a general-relativistic model of cosmological expansion dominated by a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the deceleration parameter, and the age of the universe.
Abstract: The Proca generalization of electrodynamics admits the possibility that the universe could possess a net electric charge uniformly distributed throughout space, while possessing no electric field. A general-relativistic model of cosmological expansion dominated by such a charged background has been calculated, and is consistent with present observational limits on the Hubble constant, the deceleration parameter, and the age of the universe. However, if this cosmology applied at the present epoch, the very early expansion of the universe would have been too rapid for cosmological nucleosynthesis or thermalization of the background radiation to have occurred. Hence, domination of the present expansion by background charge appears to be incompatible with the 3-K background and big-bang production of light elements. If the present background charge density were sufficiently small (but not strictly zero), expansion from the epoch of nucleosynthesis would proceed according to the conventional scenario, but the energy due to the background charge would have dominated at some earlier epoch. This last possibility leads to equality of pressure and energy density in the primordial universe.
22 citations
TL;DR: In this paper, the growth of a black hole by radiation accretion in the early universe is analyzed in the particular case in which the inflow of radiation is purely radial, and it is shown that, under this circumstance, the black hole tends to grow at the same rate as the particle horizon of the universe.
Abstract: The growth of a black hole by radiation accretion in the early Universe is analyzed in the particular case in which the inflow of radiation is purely radial. This is done by generalizing the Einstein-Strauss vacuole model to the case of a radiation-filled universe. It is shown that, under this circumstance, the black hole tends to grow at the same rate as the particle horizon of the universe; this corresponds to an upper limit to the accretion rate.
16 citations
IBM1
TL;DR: In this paper, a model of the early universe is proposed which initially contains a zero-temperature quark phase and the entropy of the cosmic background radiation is generated by an irreversible transition to the usual radiation-dominated nucleon gas.
Abstract: A model of the early universe is proposed which initially contains a zero-temperature quark phase. The entropy of the cosmic background radiation is generated by an irreversible transition to the usual radiation-dominated nucleon gas. At recombination time the model has density fluctuations with a characteristic mass of ${10}^{6}$ solar masses.
13 citations
TL;DR: With the assumption of nonzero photon mass, the existence of the photon condensate at the early stages of the Universe's expansion is supposed as discussed by the authors. But this assumption assumes that photon mass is infinite.
9 citations
6 citations
TL;DR: In this article, the authors investigated whether a large number of primordial black holes can account for the observed microwave background in a steady state universe, and the answer is shown to be negative.
5 citations
TL;DR: In this article, the authors describe the long-term future of the universe on the basis of the current "standard models" of cosmology, and present a review of the existing cosmology models.
3 citations
TL;DR: In this article, the primordial black hole (PBH) hypothesis was proposed to reconcile the assumption of initial symmetry with the observed asymmetry, and it was shown that PBHs are ideal stores for antimatter.
Abstract: Undoubtedly complete symmetry of charge in the initial state of the Universe is an attractive idea. However, analysis of observational data1 indicates that the visible Universe contains mostly particles of positive baryon number. Attempts2–6 to reconcile the assumption of initial symmetry with this observed asymmetry have met with some difficulties. However, if one accepts that the Universe is symmetric in baryon charge, then there must be regions of space or objects which contain at least as much antimatter as the matter which we observe. We propose here that the hypothesis of primordial black holes (PBHs)7,8 offers a simple and economic solution of the problem. Because of the well-known ‘no hair’ theorems the baryonic charge of PBHs cannot be observed, and hence PBHs are ideal stores for antimatter.