Showing papers on "Particle horizon published in 1994"
TL;DR: In this article, it is shown that in the k = 0 FRW space, an impulse bulk viscosity ςinfl ~ 1060 g cm−1 s−1) acting at the phase transition at the end of the inflationary epoch corresponds to the correct entropy.
Abstract: Some aspects of viscous cosmological models, mainly of Bianchi type-I, are studied, in particular with the purpose of trying to obtain a natural explanation of why the entropy per baryon in the universe,σ ~ 109, is so large. Using the FRW metric it is first shown, in agreement with previous workers, that the expressions for the bulk viscosity as derived from kinetic theory in the plasma era is incapable of explaining the large value ofσ. However it is possible to imagine the viscosity to be an “impulse” viscosity operative in one or several phase transitions in the early universe. This is the main idea elaborated on in the present paper. It is shown that in thek = 0 FRW space, an impulse bulk viscosity ςinfl ~ 1060 g cm−1 s−1) acting at the phase transition at the end of the inflationary epoch corresponds to the correct entropy. If the space is anisotropic, it is natural to exploit the analogy with classical fluid dynamics to introduce the turbulent viscosity concept. This is finally discussed, in relation to an anisotropy introduced in the universe via the Kasner metric.
51 citations
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04 Nov 1994
TL;DR: The problem of large-scale structure of the universe geometry, dynamical systems, catastrophes definition of a galaxy cluster the bound-tree technique appearance of matter distribution statistical methods filaments and light-travel effects the cosmic background radiation as a tracer of geometry as mentioned in this paper.
Abstract: The problem of large-scale structure of the universe geometry, dynamical systems, catastrophes definition of a galaxy cluster the bound-tree technique appearance of matter distribution statistical methods filaments and light-travel effects the cosmic background radiation as a tracer of geometry of the universe
44 citations
TL;DR: In this article, a model of a stationary universe is proposed, where time is defined as a local and quantum-mechanical notion in the sense that it is defined for each local and QM system consisting of finite number of particles.
Abstract: A model of a stationary universe is proposed. In this framework, time is defined as a local and quantum-mechanical notion in the sense that it is defined for each local and quantum-mechanical system consisting of finite number of particles. The total universe consisting of infinite number of particles has no time associated. It is a stationary bound state of the total Hamiltonian of infinite degrees of freedom. The quantum mechanics and the theory of general relativity are consistently united in this context if one uses this notion of local and quantum-mechanical time. As one of the consequences, the Einstein-Podolsky-Rosen paradox is resolved. The Hubble red-shift is explained as a consequence of general relativity which is consistent with quantum mechanics. This does not require us to argue on the beginning nor the end of the universe. The universe just exists without time.
22 citations
TL;DR: In this article, the evolution of a universe with Brans-Dicke gravity and nonzero curvature is investigated, and the authors find solutions to the equations of motion during the radiation dominated era.
18 citations
TL;DR: In this article, the authors demonstrate a possible explanation of the observed periodicity of the large-scale distribution of galaxies as an effect of the global rotation of the universe, and demonstrate that it can be explained as a function of the number of galaxies in the universe.
Abstract: We demonstrate a possible explanation of the observed periodicity of the large-scale distribution of galaxies as an effect of the global rotation of the universe.
13 citations
TL;DR: In an FRW universe, the local spin density of the Dirac spinor field is subject to precession whose rate is determined by the electric-dipole density and by the absolute velocity relative to the cosmic rest system as discussed by the authors.
Abstract: In an FRW universe, the local spin density of the Dirac spinor field is subject to precession whose rate is determined by the electric-dipole density and by the absolute velocity relative to the cosmic rest system.
7 citations
TL;DR: In this paper, the authors examined light exchange in fixed spatial coordinates rather than the Robertson-Walker (RW) comoving coordinates both because it provides a graceful transition from special relativity and because it is an interesting exercise by itself.
Abstract: The standard model of light exchange in the expanding universe is usually expressed in the Robertson–Walker (RW) proper distance as a function of RW cosmic time, a standard time which is the same for all points on the expanding spatial coordinates. In these coordinates, light like the cosmic microwave background emitted early in the universe close to the origin recedes before it approaches the earth, taking about one‐third of the universe’s age, t0, to achieve a maximum distance of about ct0/2, traveling outward an average velocity (maximum distance divided by elapsed cosmic time) about 50% greater than c, the normal speed of light in the absence of gravity. This paper examines this light exchange in fixed spatial coordinates rather than the RW comoving coordinates both because it provides a graceful transition from special relativity and because it is an interesting exercise by itself. For this the array of noninertial observers at fixed distances from the origin must have peculiar velocities, moving tow...
7 citations
TL;DR: In this paper, the authors consider the possibility that the universe did not necessarily inflate, but was filled with a network of evolving wormholes connecting otherwise causally disjoint regions.
Abstract: Measurements of the cosmic microwave background (cmb) radiation provide the strongest evidence for the isotropy of the observable universe on the largest scales. However, thecmb is received from regions which were not in causal contact at the time of last scattering. This is the horizon problem and the generally accepted solution is to invoke an inflationary period in the early universe. We consider the possibility that the universe did not necessarily inflate, but was filled with a network of evolving wormholes connecting otherwise causally disjoint regions. These wormholes emerged naturally from the Planck epoch and need only have stayed open for a very brief time (δt<10−34 sec) in order to have thermalized the early universe.
6 citations
TL;DR: In this article, the energy production through expansion of the universe is studied for the Dirac spinor field in all three types of Robertson-Walker universes, and the physical properties of the cosmological solutions to Dirac equation over any RW background are studied in detail.
Abstract: The energy production through expansion of the universe is studied for the Dirac spinor field in all three types of Robertson-Walker universes. Only in the open case is the matter production unlimited (closed universe: limited; flat universe: impossible). The physical properties of the cosmological solutions to the Dirac equation over any RW background are studied in detail.
6 citations
01 May 1994
TL;DR: In this article, the authors explore the evolution of topological defects in an open universe and explore the relationship between angle and lenght in a COBE model with a galaxy power spectrum consistent with the power spectrum inferred from galaxy surveys.
Abstract: This talk will explore the evolution of topological defects in an open universe The rapid expansion of the universe in an open model slows defects and suppresses the generation of CBR fluctuations at large angular scale as does the altered relationship between angle and lenght in an open universe Defect models, when normalized to COBE in an open universe, predict a galaxy power spectrum consistent with the galaxy power spectrum inferred from the galaxy surveys and do not require an extreme bias Neither defect models in a flat universe nor standard inflationary models can fit either the multipole spectrum or the power spectrum inferred from galaxy surveys
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TL;DR: In this article, a cosmological model in which the early universe is dominated by the equation of state p = −ϱ 3 corresponding to a coasting cosmology is considered and the temperature is almost absolute zero at the beginning and the universe quickly heats up to maximum temperature.
TL;DR: Inflationary cosmology makes the universe "eternal" and provides for recurrent universe creation, ad infinitum, making it also plausible to assume that “our” Big Bang was also preceeded by others as discussed by the authors.
Abstract: Inflationary cosmology makes the universe “eternal” and provides for recurrent universe creation, ad infinitum — making it also plausible to assume that “our” Big Bang was also preceeded by others, etc.. However, GR tells us that in the “parent” universe's reference frame, the newborn universe's expansion will never start. Our picture of “reality” in spacetime has to be enlarged.
TL;DR: In this paper, a theory of gravitation in flat space-time is applied to homogeneous, isotropic cosmological models and a two-component fluid model consisting of dust and of a background field is studied.
Abstract: A previously studied theory of gravitation in flat space-time is applied to homogeneous, isotropic cosmological models. In addition to radiation a two-component fluid model consisting of dust and of a background field is studied. This universe starts from a nonsingular state and expands for ever. The energy of radiation, of dust and of the background are emerged from the gravitational energy. Entropy is produced. The age of the universe is infinite measured in units of absolute time whereas the proper-time of the universe is finite. The sum of the density parameters of dust, of radiation and of the background field is about one. There is no flatness and no monopole problem.
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TL;DR: In this paper, the gravitaional force produced by a point particle, like the sun, in the background of the static Einstein universe is studied, and both the approximate solution in the weak field limit and exact solution are obtained.
Abstract: The gravitaional force produced by a point particle, like the sun, in the background of the static Einstein universe is studied. Both the approximate solution in the weak field limit and exact solution are obtained. The main properties of the solution are {\it i}) near the point particle, the metric approaches the Schwarzschild one and the radius of its singularity becomes larger than that of the Schwarzschild singularity, {\it ii}) far from the point particle, the metric approaches the static Einstein closed universe. The maximum length of the equator of the universe becomes smaller than that of the static Einstein universe due to the existence of the point particle. These properties show the strong correlation betweem the particle and the universe.
TL;DR: In this paper, a two-dimensional model of gravity with the cosmological constant as a dynamical variable is considered, and the effective Cosmological Constant is derived when the universe has no initial boundary.
Abstract: We consider a two-dimensional model of gravity with the cosmological constant as a dynamical variable. The effective cosmological constant is derived when the universe has no initial boundary. It turns out to be extremely small if the universe is sufficiently large
TL;DR: In this paper, an exact formula for the age of the universe in terms of the density parameter is found that may be used instead of the approximate one in current use, among other purposes, for the estimate of an upper bound of relic particles in the present universe.
Abstract: An exact formula for the age of the universe in terms of the density parameter is found that may be used instead of the approximate one in current use, among other purposes, for the estimate of an upper bound of relic particles in the present universe.
01 May 1994
TL;DR: In this article, the spectral slope of density perturbations and the possibility of getting power-spectra with less large-scale power than the Harrison-Zel'dovich case were discussed.
Abstract: We review some general properties of perturbations in the space-time curvature, which are produced during an inflationary ear in the early Universe and their possible imprints on the observed large angular scale temperature fluctuations of the Cosmic Microwave Background. Specifically, we consider the spectral slope of density perturbations and we discuss the possibility of getting power-spectra with less large-scale power than the Harrison-Zel'dovich case.
TL;DR: In this paper, it is shown that from the assumption that the physical vacuum realizes a state near the maximum of the effective potential, it is possible to obtain many of the observed properties of the distribution of galaxies in the universe.
Abstract: It is shown that from the assumption that the physical vacuum realizes a state near the maximum of the effective potential it is possible to obtain many of the observed properties of the distribution of galaxies in the universe.