Showing papers on "Particle horizon published in 1986"
TL;DR: It is demonstrated that the recently discovered large-scale structure of the Universe (voids and filaments) can be explained by cosmic strings and the presence of pointlike structures (''knobs'') of masses >10/sup 7/M/sub cirdot/ in the vicinity of larger galaxies is predicted.
Abstract: We wish to demonstrate that the recently discovered large-scale structure of the Universe (voids and filaments) can be explained by cosmic strings. We also predict the presence of pointlike structures (''knobs'') of masses >10/sup 7/M/sub cirdot/ in the vicinity of larger galaxies. The present analysis is limited to order-of-magnitude estimates. A detailed analysis would necessarily have to go into the full nonlinear theory of the growth of fluctuations in the Universe.
101 citations
TL;DR: The possible thermal histories of the universe during the epoch z = 10-1000 are studied in this article, where expressions for fractional ionization and electron temperature are given in the case of homogeneous heating as a function of the parameters of arbitrary ionizing sources.
Abstract: The possible thermal histories of the universe during the epoch z = 10-1000 are studied. Expressions for the fractional ionization and electron temperature are given in the case of homogeneous heating as a function of the parameters of arbitrary ionizing sources. It is shown that present and future limits on spectral distortions to the microwave background radiation do not provide very restrictive constraints on possible thermal histories of the universe. If H(0) = 50 km/s Mpc, the universe could have been completely ionized throughout its history with no observable spectral effects even if Omega = 1 and the universe is entirely made of baryons. Heating by cosmic rays and very massive stars is briefly discussed.
27 citations
TL;DR: The universe is filled with thermal radiation having a current temperature of 2.75 K, and this radiation furnishes strong evidence that the Big Bang cosmology best describes the authors' expanding universe from an incredibly hot, compacted early stage until now.
Abstract: The universe is filled with thermal radiation having a current temperature of 2.75 K. Originating in the very early universe, this radiation furnishes strong evidence that the Big Bang cosmology best describes our expanding universe from an incredibly hot, compacted early stage until now. The model can be used to extrapolate our physics backward in time to predict events whose effects might be observable in the 2.75 K radiation today. The spectrum and isotropy are being studied with sophisticated microwave radiometers on the ground, in balloons, and in satellites. The results are as predicted by the simple theory: the spectrum is that of a blackbody (to a few percent) and the radiation is isotropic (to 0.01 percent) except for a local effect due to our motion through the radiation. However, a problem is emerging. Primordial fluctuations in the mass density, which later became the great clusters of galaxies that we see today, should have left an imprint on the 2.75 K radiation—bumpiness on the sky at angular scales of about 10 arc minutes. They have not yet been seen.
25 citations
TL;DR: In this article, the authors investigated cosmological solutions in Kaluza-Klein models with and without an anti-symmetric tensor field and showed that the universe can evolve into a four-dimensional world with compactified extra dimensions in later time.
25 citations
TL;DR: In this paper, the authors survey recent theoretical ideas regarding the possible value of the present total density of the universe and show how physically realistic cosmological models containing small deviations from isotropy allow observations of intrinsically general relativistic effects on the microwave background to determine whether or not the Universe is open or closed no matter how close the total density lies to the critical value.
Abstract: We survey recent theoretical ideas regarding the possible value of the present total density of the Universe and show how physically realistic cosmological models containing small deviations from isotropy allow observations of intrinsically general relativistic effects on the microwave background to determine whether or not the Universe is open or closed no matter how close the total density lies to the critical value. Applications of these results to inhomogeneous cosmological models, cosmic vorticity, and observational studies of the microwave-background-radiation isotropy are also discussed.
23 citations
TL;DR: In this article, it is shown that, when the dimensionality of the kinetic energy term is increased in Einstein's field equations for the Friedmann-Robertson-Walker metric, stable bound states of the universe are only found forn=2, 3 and 4.
Abstract: It is shown that, when the dimensionality of the kinetic-energy term is increased in Einstein’s field equations for the Friedmann-Robertson-Walker metric inn dimensions, in the absence of a pressure term, stable bound states of the Universe are only found forn=2, 3 and 4. With the further assumption that space is closed, together with a suitable application of Mach’s principle, the casesn=2, 4 can be excluded, so that one has a cosmological approach to deriving the three-dimensionality of space. A speculative way to resolve the «short age» problem of a Ω>1 Universe is also described.
18 citations
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TL;DR: In this paper, the second law of thermodynamics in the frame of general relativity is reconsidered in the case of an istotropic homogeneous universe, and there appears a direct link between the cosmological state of the universe, as expressed in terms of conformal coordinates, and quantities such as energy density, pressure, and entropy associated with the description of nature.
Abstract: The formulation of the second law of thermodynamics in the frame of general relativity is reconsidered in the case of an istotropic homogeneous universe. We show that there appears then a direct link between the cosmological state of the universe, as expressed in terms of conformal coordinates, and quantities such as energy density, pressure, and entropy associated with the description of nature. In the early universe there appears a kind of phase transition due to transfer of gravitational energy to matter associated with the cosmological expansion if the universe starts with a non-Euclidian (space) state. As a result, we may envisage the possibility of a “cold big-bang model,” in which the universe would start at zero temperature and entropy. The temperature goes then through a maximum before entering the present area of cooling related to adiabatic expansion.
16 citations
TL;DR: In this article, the Robertson-Walker geometry in an empty five-dimensional universe is derived and the effective four-dimensional evolution is analyzed, and the radius of the compact fifth dimension is regarded as a non-static quantity.
11 citations
TL;DR: In this article, the evolution of spherical radiation-filled voids in a spatially flat Robertson-Walker background is studied within the context of the general relativistic thin-wall approximation.
Abstract: The evolution of spherical radiation-filled voids in a spatially flat Robertson-Walker background is studied within the context of the general relativistic thin-wall approximation. This work extends previous discussions of vacuum voids. It is found that the inclusion of radiation within the void has significant quantitative and important qualitative effects on the evolution of the void. In particular, it is found that voids which do not collapse grow, at late times, like the particle horizon.
11 citations
TL;DR: In this article, the chaotic inflationary model of the early universe is studied within the framework of an anisotropic Kantowski-Sachs cosmology, and it is shown that the chaotic model naturally leads to an inflationary phase which also helps in the isotropization of the universe.
Abstract: The chaotic inflationary model of the early universe, proposed by Linde is studied within the framework of an anisotropic Kantowski-Sachs cosmology. It is shown that the chaotic model naturally leads to an inflationary phase which also helps in the isotropization of the universe.
TL;DR: It is shown that the lifetime of the X-italic particle in cosmological models dominated by unstable weakly interacting particles with lifetime on the order of the age of the Universe is close to those required.
Abstract: We consider cosmological models in which the mass of the Universe is dominated by unstable weakly interacting particles (X-italic) with lifetime on the order of the age of the Universe. In our picture the mass of galaxies and clusters is dominated by undecayed X-italic particles while the Universe is closed in the large by their relativistic decay products. Quantitative results are given based on Turner's equations for evolution in the presence of dominant unstable particles. Several possibilities for the X-italic particle are considered. Lifetimes are calculated within these scenarios and shown to be close to those required.
TL;DR: In this article, it is shown that if our universe is described by the cosmological, classical, Einstein equations based on a manifold M 4 × G where G is the product of any number of Ricci flat manifolds (as is expected to occur in superstring theories), then our universe must, today, be radiation dominated.
TL;DR: In this paper, initial conditions in a higher-dimensional cosmology that can achieve our present universe are investigated, and it is shown that most of the created universes can reach our present universes.
TL;DR: In this paper, the evolution of superheated particles in the Friedmann universe is considered under the assumption of the asymptotic behavior of the scattering cross sections in the high-energy region.
Abstract: The evolution of superheated particles in the Friedmann universe is considered under the assumption of the asymptotic behavior of the scattering cross sections in the high-energy region. We show that there is no local thermodynamic equilibrium at early stages and conclude that the nature of cosmic rays can be explained on cosmological grounds.
TL;DR: In this article, it is shown that the Friedmann equation for the radiation-dominated phase of the evolution of the universe is valid even for the matter-dominated era, assuming the validity of Mach's Principle.
Abstract: In the introductive section a deeper specification is made of the physical meaning of the terms in the Friedmann Equation (FE). After that, assuming validity of Mach's Principle, it is deduced (Section 2) that the FE for the radiation-dominated phase of the evolution of the Universe (which is considered to be closed) is valid even for the matter-dominated era. On the other hand, such a form of the FE is shown to be irrelevant when used for deducing how the frequency of the 3K-photons depends on the radius of the Universe. The solution of the dilemma turns out to have its roots in the way in which the relativistic gravitational potentials are composed, together with the fact that the cosmic potential of the closed Universe is equal to −1. Consequently, the equation one uses for the matter-dominated era is shown to be proper for both the main phases of the cosmological evolution (Section 3). In Section 4, the deduction of the critical density-value is revised, and the new result shortly discussed. In Section 5 it is concluded that there is only one possible value for the maximum radius of our Universe, specific for the initial condition due to the FE. Nevertheless, it is not excluded that other smaller universes can exist. In the final section a modified ‘soabubble’ analogy with the first law of thermodynamics is used to describe ‘the dynamics’ of the cosmological expansion, and, in this context, the importance of Mach's Principle is pointed out.
01 Mar 1986
TL;DR: In this article, it was shown that all but a small subset of the Bianchi models undergo inflation and any initial anisotropy is so strongly damped that if sufficient inflation occurs to solve the flatness/horizon problems the Universe today would still be very isotropic.
Abstract: The promise of the inflationary Universe scenario is to free the present state of the Universe from extreme dependence on initial data. Paradoxically, inflation is usually analyzed in the context of the homogeneous and isotropic Robertson-Walker (RW) cosmological models. We show that all but a small subset of the homogeneous models (the Bianchi models) undergo inflation. Any initial anisotropy is so strongly damped that if sufficient inflation occurs to solve the flatness/horizon problems the Universe today would still be very isotropic. Some of the Bianchi models will eventually (in the exponentially distant future) become very anisotropic again. 15 refs.
TL;DR: In this paper, it was shown that Hartly-Hawking's wave function of the ground state of the universe is equal to zero when its arguments (i.e. the universe and matter fields in it) satisfy some topological conditions.
TL;DR: In this paper, the evolution of the universe in the framework of the relativistic theory of gravitation is considered and it is proved that under this assumption there exists only a flat infinite universe.
Abstract: The evolution of the Universe in the framework of the relativistic theory of gravitation is considered. It is assumed that in Minkowski coordinates the matter is at rest in the gravitational field which it produces and is distributed homogeneously and isotropically. It is proved that under this assumption there exists only a flat infinite Universe.
TL;DR: In this article, a solution of the Einstein field equation in a Bianchi-V type universe with incoherent radiation is presented, and it is shown that, with the lapse of time, the model approaches the state of isotropic expansion.
01 Jan 1986
TL;DR: Sandage as discussed by the authors pointed out the agreement of three totally independent time scales, i.e. the age of the oldest stars, the ages of the radioactive elements, and the expansion age.
Abstract: It is appropriate here to note the 60th birthday Allan Sandage has celebrated last month and who — in 1968 — first pointed out in a paper entitled “The Time Scale of Creation” [1] the amazing agreement of three totally independent time scales, i.e. the age of the oldest stars, the age of the radioactive elements, and the expansion age of the universe. During the last almost 20 years these ages have been revised numerically, but the agreement persists.
17 Dec 1986-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: Observations of the chemical composition of the Universe interpreted in terms of the hot Big Bang cosmological theory suggest that this hidden matter cannot all be of baryonic form but must consist of weakly interacting elementary particles.
Abstract: Matter in the Universe can be detected either by the radiation it emits or by its gravitational influence. There is a strong suggestion that the Universe contains substantial hidden matter, mass without corresponding light. There are also arguments from elementary particle physics that the Universe should have closure density, which would also imply hidden mass. Observations of the chemical composition of the Universe interpreted in terms of the hot Big Bang cosmological theory suggest that this hidden matter cannot all be of baryonic form but must consist of weakly interacting elementary particles. A combination of observations and theoretical ideas about the origin of large-scale structure may demand that these particles are of a type which is not yet definitely known to exist.
TL;DR: In this article, it was shown that the observed part of the universe may in first approximation be the interior of a giant anticollapsing body having a boundary beyond the particle horizon.
Abstract: The known physical laws do not exclude the existence of anticollapsing bodies in nature (anticollapse is a gravitational collapse with time reversal). In the paper it is shown that the metagalaxy, i.e. the observed part of the universe, may in first approximation be the interior of a giant anticollapsing body having a boundary beyond the particle horizon. This is the “anticollapse model” of the metagalaxy. The advantage of this model follows from the fact that some anisotropies in the metagalaxy, e.g. the cosine-anisotropy of the intensity of cosmic background radiation, the cosine-anisotropy of the Hubble parameter at a given distance, the gradient of the mean matter density, etc. are already considered in first approximation. The theoretical considerations about anticollapse show and the present-day cosmological observations support the opinion that the anticollapse model of the metagalaxy is better than the usual Friedmann model.
01 Sep 1986
TL;DR: In this paper, it was shown that the small distance Wheeler-DeWitt equation governing the quantum state of the universe corresponds to a nonzero energy and is equivalent to a Lie-admissible wave equation for the observable universe.
Abstract: It is shown that the small-distance Wheeler-DeWitt equation governing the quantum state of the universe corresponds to a nonzero energy and is equivalent of a Lie-admissible wave equation for the observable universe Therefore the functional wave function is intrepreted as the prabability amplitude for the universe to have been created from some sort of physical reality with which it is interacting
TL;DR: The wave function of the universe was proposed by W.S. W. Hawking as mentioned in this paper, who showed that at any given nonzero energy density, the universe is most probably infinitely large.
Abstract: S. W. Hawking's proposal for the wave function of the universe, if correct, determines the conditional probabilities for all properties of the universe. In a simple minisuperspace model it predicts that at any given nonzero energy density, the universe is most probably infinitely large.
01 Jan 1986
TL;DR: In this paper, it is shown that neutrino degeneracy will not permit the universe to be closed by nucleons, since neutrinos are virtually unobservable and lepton asymmetry is possible.
Abstract: Since relic neutrinos are virtually unobservable, a large - but undetectable - lepton asymmetry is possible. Cosmological constraints can provide bounds to such a universal neutrino degeneracy. The weakest constraint is from considerations of the age and density of the present Universe. More significant constraints follow from the formation of structure in the expanding Universe. The most stringent bounds to neutrino degeneracy follow from comparisons of the predictions of Big Bang Nucleosynthesis with the observed abundances of the light elements. All these approaches are reviewed and constaints to neutrino degeneracy derived. It is shown that neutrino degeneracy will not permit the Universe to be “closed” by nucleons.
TL;DR: In this paper, it was shown that the non-oscillatory solution coincides with the adiabatic solution up to 6.6 order for all the evolution of the universe with cosmological interest.
Abstract: As the red shift shows no sign of oscillatory behavior in an expanding universe we postulate that the energyω
k
of a scalar field does not oscillate in such a universe. In the massive case, expanding the differential equation forω
k
in mass powers, we find that the nonoscillatory solution coincides with the adiabatic solution up to them
6 order. We also demonstrate that this solution is unique for all the evolution of the universe with cosmological interest. Using the nonoscillatory solution as the one that defines the good vacuum state, we compute the particle and energy creation for a simple model of expanding universe. Both quantities turn out to be finite.
TL;DR: In this paper, a cosmological model of the universe based on the Newtonian mechanics and classical field theory is proposed, and the essential ingredient of this model is the existence of a special kind of physical field in the Universe whose source is the mass current.
Abstract: We propose a cosmological model of the Universe based on the Newtonian mechanics and classical field theory. The essential ingredient of this model is the existence of a special kind of physical field in the Universe whose source is the mass current. In the early Universe this field reached such large values that it produced matter from the vacuum fluctuation. The classical dynamical equations for the co-moving sphere in the presence of this field are enlarged by a new term which causes an inflation-like expansion. It accounts also for the hot initial stage of the early Universe and has several important cosmological consequences.
01 Jan 1986
TL;DR: The age of the oldest objects in the universe has been shown to be smaller than the age of space-time arena itself as discussed by the authors, which is not the case for the universe itself.
Abstract: The age of the oldest objects in the universe has obviously to be smaller than the age of the space-time arena itself.