Showing papers on "Cosmology published in 1993"
Book•
19 Apr 1993
TL;DR: Peebles as mentioned in this paper provides a comprehensive overview of today's physical cosmology, including the history of the discovery of the expanding universe, and discusses the most notable recent attempts to understand the origin and structure of the universe.
Abstract: During the last twenty years, dramatic improvements in methods of observing astrophysical phenomena from the ground and in space have added to our knowledge of what the universe is like now and what it was like in the past, going back to the hot big bang. In this overview of today's physical cosmology, P.J.E. Peebles shows how observation has combined with theoretical elements to establish the subject as a mature science, while he also discusses the most notable recent attempts to understand the origin and structure of the universe. A successor to Peebles's classic volume Physical Cosmology (Princeton, 1971), the book is a comprehensive overview addressed not only to students but also to scientists active in fields outside cosmology. The first chapter of the work presents the elements of physical cosmology, including the history of the discovery of the expanding universe. The second, on the cosmological tests that measure the geometry of spacetime, discusses general relativity theory as the basis for the tests, and then surveys the broad variety of ways the tests can be applied with the new generations of telescopes and detectors. The third chapter deals with the origin of galaxies and the large-scale structure of the universe, and reviews ideas about how the evolution of the universe might be traced back to very early epochs when structure originated. Each section of these chapters begins with an introduction that can be understood with no special knowledge beyond undergraduate physics, and then progresses to more specialized topics. P.J.E. Peebles is Albert Einstein Professor of Science at Princeton University. He is a Fellow of the American Academy of Arts and Sciences and the Royal Society.
3,399 citations
CERN1
TL;DR: The duality-type symmetries of string cosmology naturally lead us to expect a pre-big-bang phase of accelerated evolution as the dual counterpart of the decelerating expansion era of standard cosmology as discussed by the authors.
876 citations
TL;DR: In this article, the authors investigated how the rms linear fluctuation in the mass distribution on scales of 8 h − 1 Mpc 1 (denoted by σ 8 ) is constrained by the masses and abundances of rich clusters of galaxies.
Abstract: We investigate how the rms linear fluctuation in the mass distribution on scales of 8 h −1 Mpc 1 (denoted by σ 8 ) is constrained by the masses and abundances of rich clusters of galaxies. The derived value of σ 8 is almost independent of the shape of the fluctuation spectrum, but depends strongly on the cosmological density parameter. We find σ 8 ≃ 0.52-0.62 for a critical density universe, and σ 8 ≃ 1.25-1.58 for a spatially flat universe with Ω 0 = 0.2. Our results conflict with the high amplitude inferred for an Ω = 1 cold dark matter universe from the COBE anisotropy measurements and advocated on other grounds by Couchman & Carlberg
525 citations
TL;DR: In this paper, the spontaneous breaking of local Lorentz invariance in the early Universe, associated with a first order phase transition at a critical time, generates a large increase in the speed of light and a superluminary communication of information, allowing all regions in the Universe to be causally connected.
Abstract: The spontaneous breaking of local Lorentz invariance in the early Universe, associated with a first order phase transition at a critical time tc, generates a large increase in the speed of light and a superluminary communication of information occurs, allowing all regions in the Universe to be causally connected. This solves the horizon problem, leads to a mechanism of monopole suppression in cosmology and can resolve the flatness problem. After the critical time tc, local Lorentz (and diffeomorphism) invariance is restored and light travels at its presently measured speed. The kinematical and dynamical aspects of the generation of quantum fluctuations in the superluminary Universe are investigated. A scale invariant prediction for the fluctuation density amplitude is obtained.
310 citations
TL;DR: In this article, the authors consider whether current notions about superstring theory below the Planck scale are compatible with cosmology and find that the anticipated form for the dilaton interaction creates a serious roadblock for inflation and makes it unlikely that the universe ever reaches a state with zero cosmological constant and time independent gravitational constant.
261 citations
CERN1
TL;DR: The baryon asymmetry of the Universe which would arise during a first-order electroweak phase transition due to minimal-standard-model processes agrees in sign and magnitude with the observed baryonic excess and for reasonable Kobayashi-Maskawa parameters and mt in the expected range.
Abstract: We calculate the baryon asymmetry of the Universe which would arise during a first-order electroweak phase transition due to minimal-standard-model processes. It agrees in sign and magnitude with the observed baryonic excess, for reasonable Kobayashi-Maskawa parameters and mt in the expected range, and plausible values of bubble velocity and other high temperature effects. © 1993 The American Physical Society.
186 citations
TL;DR: Because tensor perturbations give rise to the anisotropy of the cosmic background radiation (CBR) solely through the Sachs-Wolfe effect, the transfer function is provided, and it is shown that it is unlikely that the stochastic background of gravity waves can be detected directly in the foreseeable future.
Abstract: In principle, the tensor metric (gravity-wave) perturbations that arise in inflationary models can, beyond probing the underlying inflationary model, provide information about the Universe: ionization history, presence of a cosmological constant, and epoch of matter-radiation equality. Because tensor perturbations give rise to the anisotropy of the cosmic background radiation (CBR) solely through the Sachs-Wolfe effect we are able to calculate analytically their contribution to the variance of the multipole moments of the CBR temperature anisotropy. In so doing, we carefully take account of the effect of tensor perturbations that entered the Hubble radius during both the matter-dominated and radiation-dominated epochs by means of a transfer function. (Previously, only those modes that entered during the matter era were properly taken into account.) The striking feature in the spectrum of multipole amplitudes is a dramatic falloff for l\ensuremath{\gtrsim} \ensuremath{\surd}1+${\mathit{z}}_{\mathrm{LSS}}$ , where ${\mathit{z}}_{\mathrm{LSS}}$ is the redshift of the last-scattering surface, which depends upon the ionization history of the Universe. Finally, using our transfer function we provide a more precise formula for the energy density in stochastic gravitational waves from inflation, and, using the Cosmic Background Explorer Differential Microwave Radiometer (COBE DMR) quadrupole normalization, we express this energy density in terms of the ``tilt'' of the spectrum of tensor perturbations alone and show that it is unlikely that the stochastic background of gravity waves can be detected directly in the foreseeable future.
184 citations
TL;DR: In this article, a universe is envisioned in which there was a major creation episode when the mean universal density was about 10 to the -27 g/cu cm. Explicit equations are given for the creation of matter; in a cosmological approximation, these equations lead to expressions for the time-dependence of the cosmology scale factor S(t), but do not entail, as big bang cosmology does, that S( t) tend to zero at some finite time t.
Abstract: A universe is envisioned in which there was a major creation episode when the mean universal density was about 10 to the -27 g/cu cm. Explicit equations are given for the creation of matter; in a cosmological approximation, these equations lead to expressions for the time-dependence of the cosmological scale factor S(t), but do not entail, as big bang cosmology does, that S(t) tend to zero at some finite time t. The equations therefore possess a universality that is absent from big bang cosmology. Creation occurs when certain conservation equations involving the gradient of a scalar field C(i) are satisfied.
180 citations
TL;DR: In particular, non-standard models often allow for a larger range of conditions to be present in the early universe than those allowed by the SBB while satisfying observational constraints such as the inferred primordial isotopic abundances and the number of neutrino species derived from recent e+e− collider experiments as discussed by the authors.
154 citations
TL;DR: Full radiative transport calculations of the two contributions of gravitational waves are described and it is shown how anisotropy experiments probing large- and small-angular scales can combine to distinguish the imprint due to gravitational waves.
Abstract: Long-wavelength gravitational waves can induce significant temperature anisotropy in the cosmic microwave background. Distinguishing this from anisotropy induced by energy density fluctuations is critical for testing inflationary cosmology and theories of large-scale structure formation. We describe full radiative transport calculations of the two contributions and show that they differ dramatically at angular scales below a few degrees. We show how anisotropy experiments probing large- and small-angular scales can combine to distinguish the imprint due to gravitational waves.
144 citations
TL;DR: In this article, a large class of solutions for second-order irrotational perturbations is derived in the framework of the Lagrangian theory of gravitational instability of a homogeneous and isotropic universe investigated in earlier papers.
Abstract: A large class of solutions for second-order irrotational perturbations is derived in the framework of the Lagrangian theory of gravitational instability of a homogeneous and isotropic universe investigated in earlier papers. The solutions are evaluated in detail for perturbations in a flat background universe. The form of the solutions is designed for use in studies of the formation of large-scale structure from generic initial conditions. Some general remarks on the properties of the solutions are made. The result is illustrated by a special case and discussed. In particular, it is found that sheet-like structures stay compact after shell-crossing (as in the competing adhesion model), and that the collapse of first objects occurs earlier (as expected from numerical simulations)
01 Jan 1993
TL;DR: Hoyle as discussed by the authors gave a critical overview of the structure of the universe and its evolution from the Big Bang to the present day, including the formation of structures in the universe, as well as local observations of cosmological significance.
Abstract: Foreword by Professor Sir Fred Hoyle 1. The large-scale structure of the universe 2. General relativity 3. From relativity to cosmology 4. The Friedman models 5. Relics of the Big Bang 6. The very early universe 7. The formation of structures in the universe 8. Alternative cosmologies 9. Local observations of cosmological significance 10. Observations of distant parts of the universe 11. A critical overview.
TL;DR: The distinction between Hubble's linear redshift distance z(L) law and the linear velocity distance V(L), which emerged later is discussed, using first the expanding space paradigm and then the Robertson-Walker metric as discussed by the authors.
Abstract: The distinction between Hubble's linear redshift-distance z(L) law and the linear velocity-distance V(L) law that emerged later is discussed, using first the expanding space paradigm and then the Robertson-Walker metric. The z(L) and V(L) laws are theoretically equivalent only in the limit of small redshifts, and failure to distinguish between the two laws obscures the basic elementary principles of modern cosmology. The linear V(L) law [V=HL, where H(t) is the Hubble term] applies quite generally in expanding homogeneous and isotropic cosmological models, and recession velocities can exceed the velocity of light
TL;DR: In this article, the evolution of the physical state of a representative piece of the universe has been studied, including not only the dynamics of dark matter, but also the hydrodynamics of the gaseous component.
Abstract: We have supplemented our code, which computes the evolution of the physical state of a representative piece of the universe to include, not only the dynamics of dark matter (with a standard PM code), and the hydrodynamics of the gaseous component (including detailed collisional and radiative processes), but also galaxy formation on a heuristic but plausible basis. If, within a cell the gas is Jeans unstable, collapsing, and cooling rapidly, it is transformed to galaxy subunits, which are then followed with a collisionless code. These particles emit UV radiation and supernova blasts with energy efficiencies (in units of mc 2 ) equal to (e UV , e SN )=(10 −4 , 10 −4.5 )
TL;DR: In this paper, the authors report the concluding results of the HST Snapshot Survey for gravitationally lensed quasars and present tables summarizing all of the snapshot observations, with measured V-magnitudes, accurate to 0.1 mag.
Abstract: We report the concluding results of the HST Snapshot Survey for gravitationally lensed quasars. New observations of 153 high-luminosity z above 1 quasars are presented, bringing to 498 the total number of quasars observed in the survey. The new observations do not reveal new candidates for gravitational lensing. We present tables summarizing all of the snapshot observations, with measured V-magnitudes, accurate to 0.1 mag, for each of the quasars successfully observed. The observed frequency of lensing of quasars into multiple images is 3-6 out of 502, depending on whether one counts candidates that are not yet securely confirmed and cases in which clusters play a role. This frequency is in the range predicted by calculations with a vanishing cosmological constant, assuming galaxies can be modeled by unevolving isothermal spheres dominated in their centers by dark matter. The observed frequency is an order of magnitude lower than expected in such models when the universe is strongly dominated by a cosmological constant. This conclusion is, however, sensitive to the model assumptions and to the precise number of actual lensed quasars.
TL;DR: In this paper, it is shown that the standard Friedmann cosmology with k = 0 can be described equivalently in a conformal frame in which the spacetime is Minkowskian but all particle masses uniformly scale with epoch.
Abstract: It is known that the standard Friedmann cosmology with k = 0 can be described equivalently in a conformal frame in which the spacetime is Minkowskian but all particle masses uniformly scale with epoch. In a Machian theory of gravity this spacetime dependence of mass is understood in terms of inertial interactions. This picture is shown to be more versatile than standard cosmology because it allows one to interpret objects of anomalously high redshift to be 'young' objects whose particle masses are lagging behind the universal mass function. We discuss here a variety of extragalactic phenomena within the framework of this model and show that these can be understood without recourse to adjustable parameters such as evolution, cosmological constant, etc.
TL;DR: It is shown how observations of the density perturbation (scalar) spectrum and the gravitational wave (tensor) spectrum allow a reconstruction of the potential responsible for cosmological inflation.
Abstract: We show how observations of the density perturbation (scalar) spectrum and the gravitational wave (tensor) spectrum allow a reconstruction of the potential responsible for cosmological inflation. A complete functional reconstruction or a perturbative approximation about a single scale are possible; the suitability of each approach depends on the data available. Consistency equations between the scalar and tensor spectra are derived, which provide a powerful signal of inflation.
TL;DR: In this paper, it was shown that the dynamics of a spatially dosed Friedmann-Robertson-Walker universe conformally coupled to a real, free, massive scalar field, is chaotic, for large enough field amplitudes.
Abstract: We show that the dynamics of a spatially dosed Friedmann-Robertson-Walker universe conformally coupled to a real, free, massive scalar field, is chaotic, for large enough field amplitudes. We do so by proving that this system is integrable under the adiabatic approximation, but that the corresponding KAM tori break up when non-adiabatic terms are considered. This finding is confirmed by numerical evaluation of the Lyapunov exponents associated with the system, among other criteria. Chaos sets strong limitations on our ability to predict the value of the field at the big crunch, from its given value at the big bang.
TL;DR: In this article, the expected properties of the model when normalized to the anisotropy measured by COBE, for various large-scale structure observations: the CfA and IRAS galaxy power spectra, the galaxy peculiar velocities, the bulk-flow motion, the APM galaxy angular correlation function, and the cluster mass function.
Abstract: A flat, scale-free, low-density cold dark matter model with a positive cosmological constant is one of the surviving scenarios after the COBE discovery of large-scale anisotropy in the cosmic background radiation. We calculate the expected properties of the model when normalized to the anisotropy measured by COBE, for various large-scale structure observations: the CfA and IRAS galaxy power spectra, the galaxy peculiar velocities, the bulk-flow motion, the APM galaxy angular correlation function, and the cluster mass function. Several effects due to the cosmological constant and properties of primordial fluctuations from inflation are taken into account
TL;DR: In this paper, the evolution of nonlinear density fluctuations around the Jeans mass shortly after cosmological recombination is analyzed using a three-dimensional hydrodynamics/dark-matter code.
Abstract: The evolution of nonlinear density fluctuations around the Jeans mass shortly after cosmological recombination is analyzed using a three-dimensional hydrodynamics/dark-matter code. The cosmic background radiation (CBR) exerts Compton friction on free electrons in resistance to their peculiar velocities. The baryonic dynamics therefore depends strongly on the gas ionization history. For a variety of scenarios for the local reionization and in systems with or without non-baryonic components, the baryons lose angular momentum efficiently and collapse to form a compact optically thick object which would probably quickly evolve into a massive black hole
TL;DR: An exact formula is derived for the angular correlation function of the temperature fluctuations caused by squeezed gravitational waves, which can, in principle, be revealed by observations like those by the Cosmic Background Explorer.
Abstract: Cosmological perturbations generated quantum mechanically (as a particular case, during inflation) possess statistical properties of squeezed quantum states. The power spectra of the perturbations are modulated and the angular distribution of the produced temperature fluctuations of the cosmic microwave background radiation is quite specific. An exact formula is derived for the angular correlation function of the temperature fluctuations caused by squeezed gravitational waves. The predicted angular pattern can, in principle, be revealed by observations like those by the Cosmic Background Explorer.
TL;DR: In this paper, the influence of matter creation processes on the dynamics of the early universe is investigated within a phenomenological approach by using a balance law for the particle number in addition to the familiar relations for viscous fluid cosmologies.
TL;DR: In this paper, the effects of a non-zero cosmological constant on the growth, collapse and virialization of spherical and non-spherical density inhomogeneities in the post-recombination universe were investigated.
Abstract: We calculate some effects of a non-zero cosmological constant upon the growth, collapse and virialization of spherical and non-spherical density inhomogeneities in the post-recombination Universe
TL;DR: The Lyra's geometry, which is a generalization of Weyl's geometry (removing the defect of non-integrability of length transfer) and the gravitational theory and cosmology based on this geometry have been reviewed in this paper.
Abstract: The Lyra's geometry, which is a generalization of Weyl's geometry (removing the defect of non-integrability of length transfer) and the gravitational theory and cosmology based on this geometry have been reviewed. Further, cosmological models with both constant and time dependent displacement field have been discussed. Some of these models solve the singularity, entropy and horizon problems. Finally some possibilities of further problems and their investigations have been pointed out.
TL;DR: In this paper, the authors estimate the entropy associated to a background of squeezed cosmic gravitons and argue that the process of cosmological pair production from the vacuum may explain the large amount of entropy of our present universe.
TL;DR: In this article, the evolution of a diffuse baryonic medium in a flat Friedmann universe containing cold or hybrid (cold plus hot) dark matters has been studied in the linear regime.
Abstract: The evolution of a diffuse baryonic medium in a flat Friedmann universe containing cold or hybrid (cold plus hot) dark matters has been studied in the linear regime. This approximation is reasonable if one considers only the features of the intergalactic medium (IGM) on large scales where the details of energy and mass exchanges between the diffuse medium and lumpy objects (quasars and galaxies) are less important. One can then avoid a direct description of the interaction, but approximate the medium as a polytropic gas. Numerical and analytical calculations showed that for all models considered, the spectrum of density fluctuations of the IGM can be expressed on average as a proportion of those of dark matters by a factor less than 1, in which the only parameter is the Jeans length of the medium