Showing papers on "Particle horizon published in 1992"
TL;DR: In this article, a new type of explanatory mechanism is proposed to account for the fact that many of the dimensionless numbers which characterize particle physics and cosmology take unnatural values, and three possible examples of this mechanism are described.
Abstract: A new type of explanatory mechanism is proposed to account for the fact that many of the dimensionless numbers which characterize particle physics and cosmology take unnatural values. It is proposed that all final singularities 'bounce' or tunnel to initial singularities of new universes at which point the dimensionless parameters of the standard models of particle physics and cosmology undergo small random changes. This speculative hypothesis, plus the conventional physics of gravitational collapse, together comprise a mechanism for natural selection, in which those choices of parameters that lead to universes that produce the most black holes during their lifetime are selected for. If our Universe is a typical member of the ensemble that results from many generations of such reproducing universes then it follows that the parameters of our present Universe are near a local maximum of the number of black holes produced per universe. Thus, modifications of the parameters of particle physics and cosmology from their present values should tend to decrease the number of black holes in the universe. Three possible examples of this mechanism are described.
214 citations
TL;DR: The primordial nucleosynthesis and pulsar timing noise constraints on cosmic-string gravitational radiation are computed and constraints to {mu} which are more restrictive than any previous limit are found.
Abstract: The primordial nucleosynthesis and pulsar timing noise constraints on cosmic-string gravitational radiation are computed. The computation consists of a numerical integration of the Friedmann-Robertson-Walker Einstein equations which describe a universe containing radiation, dust, and a one-scale''-model cosmic-string component. The procedure takes into account the effects of the annihilations of massive particle species on the equation of state of the cosmological fluid. An expression for the power emitted per mode of oscillation by a cosmic-string loop, suggested by both analytic calculations and recent numerical simulations, is used. The results of the computation are spectra of the cosmic-string gravitational radiation at nucleosynthesis and at present. Comparison of these spectra with the observed bounds on pulsar timing noise, and the observed bound on the effective number of light neutrino species permitted by the model of nucleosynthesis, allows one to exclude a range of values of {mu}, the cosmic-string linear mass density, for certain values of {alpha}, the size of a newly formed loop as a fraction of the particle horizon radius. We find constraints to {mu} which are more restrictive than any previous limit.
179 citations
TL;DR: In this article, a stochastic approach to the theory of tunneling with baby universe formation was developed and applied also to the creation of the universe in a laboratory at a very high temperature.
126 citations
TL;DR: In this article, the authors consider a particle moving freely in the plane with elastic reflections from a periodic set of fixed convex scatterers, and show that under some natural assumptions on the free motion vector autocorrelation function, the limit distribution of the particle displacement is Gaussian, but the normalization factor is (t logt)1/2 and nott 1/2 as in the classical case.
Abstract: We study the asymptotic statistical behavior of the 2-dimensional periodic Lorentz gas with an infinite horizon. We consider a particle moving freely in the plane with elastic reflections from a periodic set of fixed convex scatterers. We assume that the initial position of the particle in the phase space is random with uniform distribution with respect to the Liouville measure of the periodic problem. We are interested in the asymptotic statistical behavior of the particle displacement in the plane as the timet goes to infinity. We assume that the particle horizon is infinite, which means that the length of free motion of the particle is unbounded. Then we show that under some natural assumptions on the free motion vector autocorrelation function, the limit distribution of the particle displacement in the plane is Gaussian, but the normalization factor is (t logt)1/2 and nott1/2 as in the classical case. We find the covariance matrix of the limit distribution.
117 citations
TL;DR: In this article, it was shown that the typical voids in the mass distribution in an Ω = 1 universe have a limiting diameter of D 130 h −1 Mpc.
Abstract: Observational constraints on the isotropy of the microwave background on angular scales greater than 1° seriously limit the possible fluctuations in the gravitational potential in the universe because of the Sachs-Wolfe effect. Consequently, they also provide a limit on the initial density inhomogeneities in the universe. We use these limits to show that the typical voids in the mass distribution in an Ω = 1 universe have limiting diameter D 130 h −1 Mpc
95 citations
TL;DR: In this article, the properties of simple, self-consistent infall models which embed an "isothermal" dark halo in an open universe are presented, which depend on one scaling parameter and two shape parameters.
Abstract: The properties of simple, self-consistent infall models which embed an 'isothermal' dark halo in an open universe are presented. These models depend on one scaling parameter and two shape parameters. The first may be taken to be the circular velocity in the inner regions, and the others to be the density of the universe, Omega, and a measure, e, of the shape of orbits. These models provide a useful description of ensembles of satellite galaxies, or of binary galaxies, because they allow explicitly for the fact that such systems have orbital periods approaching the age of the universe and so cannot have a random orbital phase.
91 citations
TL;DR: A specific model with initial conditions approaching the hot big bang is studied in detail, particularly as regards the entropy and flatness of the very early Universe.
Abstract: Decaying-vacuum singularity-free cosmological models based on the Chen-Wu ansatz of a cosmological term varying as {ital R}{sup {minus}2} where {ital R} is the scale factor of the Universe are introduced. They describe a closed ever-expanding universe of density parameter {Omega}{ge}1 and with no entropy, horizon, or monopole problems. They include and extend the critical density cosmology of Oezer and Taha. The Oezer-Taha period of phase transition during part of which the pressure is negative occurs in these models. In its wake and throughout the radiation-dominated era the Universe is Einstein--de Sitter--like with {Omega} then and subsequently near unity. Nucleosynthesis proceeds as in the standard model. Consistency with the observed helium abundance and baryon asymmetry allows a maximum vacuum energy close to the radiation energy today. The presence of this vacuum energy could be detrimental to certain theories of galaxy formation. A specific model with initial conditions approaching the hot big bang is studied in detail, particularly as regards the entropy and flatness of the very early Universe.
71 citations
TL;DR: In this article, the effects of the universal rotation on the observational cosmology were analyzed and it was shown that pure cosmic rotation does not produce neither causality voilations, nor parallax effects, nor anisotropy of the microwave background radiation.
Abstract: Cosmological models for a universe with expansion and rotation are considered. In particular, we analyse some effects of the universal rotation on the observational cosmology. It is shown that pure cosmic rotation does not produce neither causality voilations, nor parallax effects, nor anisotropy of the microwave background radiation. It can be detected by studying angular dependence of standard cosmological tests, and is directly measurable via polarization observations. The latter are used to obtain experimental estimates for the direction and value of the rotation of the universe
33 citations
TL;DR: In this paper, it was shown that the minimally sufficient duration of inflation may happen to be a very probable prediction of certain quantum cosmological models, which can make reasonable and interesting the observational search for the possible remnants of the preinflationary Universe.
Abstract: It is shown that the minimally sufficient duration of inflation may happen to be a very probable prediction of certain quantum cosmological models. This can make reasonable and interesting the observational search for the possible remnants of the preinflationary Universe.
21 citations
TL;DR: In this paper, the evolution of small density fluctuations of matters and radiation by gauge invariant formalism is summarized and the expected values of temperature anisotropies in various cosmological models are shown.
Abstract: After the recent discovery of temperature fluctuations of the cosmic microwave background radiation by COBS, the study of the temperature fluctuations becomes more and more important for understanding formations of large scale structures of the universe. The treatments for the evolution of small density fluctuations of matters and radiation by gauge invariant formalism are summarized. And the expected values of temperature anisotropies in various cosmological models are shown. Both flat and open universe models with and without the cosmological constant are considered. As for open universe models, in particular, any work had never been done by the complete treatment on large scale anisotropies. However we could find the complete formula to handle large scale temperature anisotropies and here this formula is adopted
20 citations
TL;DR: In this paper, a cosmological fluid is described by a single scalar field that undergoes a series of phase transitions, each of which denotes a change in the equation of state of the field.
Abstract: Field theory is used to describe the material content of the universe throughout its entire history, and an oscillating cosmological model without a singularity is presented. The «cosmological fluid» is described by a single scalar field that undergoes a series of phase transitions, each of which denotes a change in the equation of state of the field. It is found that an inflationary equation of state (p ∼ -p) is required in the early universe if the later epochs are to resemble the standard model
TL;DR: In this paper, it is shown that correlations between observable quantities occur over all spacetime regions and that correlations will be present in regions which lie outside of each other's horizon, which may play an important role in processes occurring in the early universe.
Abstract: It is a fundamental feature of quantum field theory that correlations between observable quantities occur over all spacetime regions. In particular, in cosmological models with horizons, such correlations will be present in regions which “lie outside of each other's horizon”. Such correlations may play an important role in processes occurring in the early universe.
TL;DR: The correction to the cold-dark-matter spatial two-point correlation function is derived and it is shown that this not only leads to no contradictions, but significantly improves the fit of theoretically predicted correlation functions to observations.
Abstract: We study a spherically symmetric Tolman-Bondi cosmological model with globally flat spatial sections {ital t}=const. We consider the model valid for the description of the Universe after matter starts to dominate. The redshift and cosmological observations in the model are examined and a simple scenario of the changes in the structure formation when compared to the standard flat Friedmann-Robertson-Walker universe is proposed. This scenario is based on the fact that in our model different parts of the Universe spend unequal periods of time in the matter-dominated era. The correction to the cold-dark-matter spatial two-point correlation function is derived. Specific cases are examined corresponding to observationally based distributions of the density. We show that this not only leads to no contradictions, but significantly improves the fit of theoretically predicted correlation functions to observations.
TL;DR: In this paper, a simple, global picture of photon exchange in the flat, matter-dominated universe is presented using relativistic cosmology Equations for the photon's recessional velocity and position relative to the receiver are derived.
Abstract: A simple, global picture of photon exchange in the flat, matter‐dominated universe is presented using relativistic cosmology Equations for the photon’s recessional velocity and position relative to the receiver are derived The results are discussed in the context of the ‘‘raisin bread universe’’ Contrary to intuition, it is shown that the Hubble recessional velocity of the emitter can exceed the speed of light for sources within the particle horizon of the receiver The model used to obtain these results can be used by introductory astronomy students to obtain the proper distance and the time‐of‐flight distance to sources with large redshifts
Journal Article•
TL;DR: On the basis of the model properties of the expansive nondecelerative universe, present temperature of cosmic microwave background and specific entropy in the era of matter, the present parameters of our universe may be exactly determined as mentioned in this paper.
Abstract: On the basis of the model properties of the expansive nondecelerative universe, present temperature of cosmic microwave background and specific entropy in the era of matter, the present parameters of our Universe may be exactly determined.
TL;DR: On the basis of model properties of the expansive non-decelerative universe, the temperature at the end of the radiation era and of the present temperature of cosmic microwave background spectrum, the present parameters of our universe can be determined as mentioned in this paper.
Abstract: On the basis of model properties of the expansive non-decelerative universe, the temperature at the end of the radiation era and of the present temperature of cosmic microwave background spectrum, the present parameters of our Universe can be determined.
TL;DR: In this article, a simple vacuum cosmological solution that is a function ofct, Gm/c2 andeG1/2/C2 is obtained in the 6D space-time-mass-charge universe which is proposed by Wesson [1] with the introduction of the sixth coordinate of charge in order to obtain a unified theory of gravity and electromagnetism along the line of his original 5D space time-mass universe.
Abstract: A simple vacuum cosmological solution that is a function ofct, Gm/c
2 andeG
1/2/C2 is obtained in the 6D space-time-mass-charge universe which is proposed by Wesson [1] with the introduction of the sixth coordinate of charge in order to obtain a unified theory of gravity and electromagnetism along the line of his original 5D space-time-mass universe [2]. It reduces to a similar solution to that of the radiation era in the 4D FRW universe through the compactifications of the extra dimensions. The trajectory of a “test particle” in the 6D universe is also studied by using the solution.
TL;DR: It is shown that a new type of phase transition, namely, a pure gravitational one, could exist for a certain range of parameters of the tree-level gravitational Lagrangian and that if the Universe had undergone this transition at late times this could be the source of structures in the Universe.
Abstract: It is shown that a new type of phase transition, namely, a pure gravitational one, could exist for a certain range of parameters of the tree gravitational Lagrangian. The symmetry-breaking mechanism responsible for the transition is due to vacuum-polarization effects of matter fields. It is argued that if the Universe had undergone this transition at late times this could be the source of structures in the Universe.
TL;DR: In this paper, the relativistic, parametric equations for radius and proper time were derived to explain the kinematics between a comoving photon emitter and receiver in a three-sphere, matter-dominated universe.
Abstract: Beginning with the general relativistic, parametric equations for radius and proper time, equations are derived which explain the kinematics between a comoving photon emitter and receiver in a three‐sphere, matter‐dominated universe. These equations can be used by introductory astronomy students to obtain kinematic information about large redshift objects in a closed universe. An example is provided. Some aspects of photon exchange in the closed, matter‐dominated universe are discussed. For example, it shown that photons with the largest redshifts can be received from the most rapidly approaching objects in this model.
TL;DR: In the early universe from the end of grand unification till the quark-hadron transition the checkerwork had been continued and the universe developed to form a simple cubic cell structure.
Abstract: In the early universe from the end of grand unification till the quark-hadron transition the checkerwork had been continued and the universe developed to form a simple cubic cell structure. The gluon configuration distinguishes between two adjacent cells. A much higher energy density is provided on the boundary of two cells tan inside each cell. The inflation of the universe enlarged this checkered structure. This situation may be responsible for the trigger of the formation of the superclusters and voids observed today
TL;DR: In this paper, the authors apply the basic concepts of general relativity to the global motion of a particle in a mass-filled universe, leading to a loss of momentum relative to the rest frame of the universe.
Abstract: Applying the basic concepts of general relativity to the global motion of a particle in a mass-filled universe leads to a loss of momentum relative to the rest frame of the Universe This loss is caused by the different running times of the gravitational interaction quanta exchanged with masses in front and behind the moving particle, if the signal velocity is limited to the speed of light Due to this ‘gravitational viscosity’ of space, the energy of photons will be reduced with the time, and thus with the distance of the emitting source This red shift is superimposed on the Doppler shift in an expanding universe A discussion of the limiting case of vanishing expansion leads to predictions about mass and radius of the Universe The value of the mass density in such a steady-state universe must be about three times the closing density discussed in Big-Bang theories The existence of the ‘gravitational viscosity’ casts severe doubts on all estimations of the age of the Universe derived from the red-shift data
TL;DR: In this paper, the authors discuss the effect of such a state of decompression on the evolution of the scale factor in a homogeneous and isotropic universe admitting energy-dependent bulk viscosity.
Abstract: For various reasons the description of matter in terms of a negative pressure (or state of tension) may be a realistic possibility in the early universe. The effect of such a state of decompression on the evolution of the scale factor in a homogeneous and isotropic universe admitting energy-dependent bulk viscosity is briefly discussed.
TL;DR: In this paper, it is shown that the flatness and horizon problems can be resolved in this framework without invoking inflation, and that it is possible to solve the horizon problem in this model.
Abstract: The hypothesis that gravity at very high energies and, hence, around the Planck epoch in the early universe is described by an action quadratic in the curvature, asymptotically free in the coupling is explored. It is shown that the flatness and horizon problems can be resolved in this framework without invoking inflation.
TL;DR: In this article, a simple derivation of the relevant expressions is given, based on the wavefront method, which is applied to observations of the quasar Q 0957+561 A, B. Assuming a simple model of this system, and using the most probable values of the observed quantities, the theory leads to an estimated Hubble age of about 17*109 years, corresponding to a Hubble parameter H0 approximately=57 km s-1 Mpc-1, which is in reasonable agreement with the results of conventional methods.
Abstract: It is explained how the Hubble age of the Universe may be determined from observation of gravitational lens images. A simple derivation of the relevant expressions is given, based on the wavefront method. The theory is applied to observations of the quasar Q 0957+561 A, B. Assuming a simple model of this system, and using the most probable values of the observed quantities, the theory leads to an estimated Hubble age of about 17*109 years, corresponding to a Hubble parameter H0 approximately=57 km s-1 Mpc-1, which is in reasonable agreement with the results of conventional methods. If the Universe has a density close to the critical mass density, this implies that the age of the Universe is about 11*109 years.
TL;DR: In this paper, a linear regression of the square of the line-spacing parameter as a polynomial in the redshift 1 + z with a vanishing linear term was proposed.
Abstract: The interpretation of the Lyman-α forests of quasars as suggested by Hoell and Priester (1991) supports a Friedmann-Lemaǐtre model for the universe. The components of the Hubble expansion rate are found by a linear regression of the square of the line-spacing parameter as a polynomial in the redshift 1 + z with a vanishing linear term. In this essay, we try to restrict the model to the special Eddington-Lemaǐtre model, which develops the deSitter expansion from the Einstein universe. We show the regression results under this restriction and discuss some of its consequences.
TL;DR: In this article, the magnitude-number count (m-N) relation of galaxies is investigated by taking into account the amplification of fluxes due to inhomogeneities, and the amplification probability function, which was derived by Futamase and Sasaki in the case of the flat dust-filled background universe, is generalized to the flat open background models which can have a non vanishing cosmological term.
Abstract: The magnitude-number count (m-N) relation of galaxies is investigated by taking into account the amplification of fluxes due to inhomogeneities. On the basis of relativistic optical equations, the amplification probability function, which was firt derived by Futamase and Sasaki in the case of the flat dust-filled background universe, is generalized to the flat open background models which can have a non-vanishing cosmological term. The validity and limitation of the probability function are investigated by comparing it with the corresponding results of the numerical simulation, where the relativistic optical equations are solved in a model universe
TL;DR: In this article, the authors use Vilenkin's method to discuss quantum cosmology with conformal scalar field and the corresponding Wheeler-DeWitt equation is derived and the wave function of the universe is calculated.