Showing papers on "Cosmology published in 2003"
TL;DR: A modified gravity, which eliminates the need for dark energy and which seems to be stable, is considered in this article, where the terms with positive powers of curvature support the inflationary epoch while the terms that serve as effective dark energy, supporting current cosmic acceleration.
Abstract: A modified gravity, which eliminates the need for dark energy and which seems to be stable, is considered. The terms with positive powers of curvature support the inflationary epoch while the terms with negative powers of curvature serve as effective dark energy, supporting current cosmic acceleration. The equivalent scalar-tensor gravity may be compatible with the simplest solar system experiments.
2,100 citations
TL;DR: The extent to which precision distance-redshift observations can map out the recent expansion history of the universe, including the acceleration-deceleration transition, and the components and equations of state of the energy density is examined.
Abstract: Exploring the recent expansion history of the universe promises insights into the cosmological model, the nature of dark energy, and potentially clues to high energy physics theories and gravitation. We examine the extent to which precision distance-redshift observations can map out the history, including the acceleration-deceleration transition, and the components and equations of state of the energy density. We consider the ability to distinguish between various dynamical scalar field models for the dark energy, as well as higher dimension and alternate gravity theories. Finally, we present a new, advantageous parametrization for the study of dark energy.
2,003 citations
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TL;DR: In this paper, the authors present an alternative explanation which allows scalar fields to evolve cosmologically while having couplings to matter of order unity in the solar system, where the mass of the fields depends on the local matter density.
Abstract: The evidence for the accelerated expansion of the universe and the time-dependence of the fine-structure constant suggests the existence of at least one scalar field with a mass of order H_0 If such a field exists, then it is generally assumed that its coupling to matter must be tuned to unnaturally small values in order to satisfy the tests of the Equivalence Principle (EP) In this paper, we present an alternative explanation which allows scalar fields to evolve cosmologically while having couplings to matter of order unity In our scenario, the mass of the fields depends on the local matter density: the interaction range is typically of order 1 mm on Earth (where the density is high) and of order 10-10^4 AU in the solar system (where the density is low) All current bounds from tests of General Relativity are satisfied Nevertheless, we predict that near-future experiments that will test gravity in space will measure an effective Newton's constant different by order unity from that on Earth, as well as EP violations stronger than currently allowed by laboratory experiments Such outcomes would constitute a smoking gun for our scenario
1,388 citations
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TL;DR: In this paper, the authors discuss the initial conditions for Population III star formation, as given by variants of the cold dark matter cosmology, and show how complementary observations, both at high redshifts and in our local cosmic neighborhood, can be utilized to probe the first epoch of star formation.
Abstract: We review recent theoretical results on the formation of the first stars in the universe, and emphasize related open questions. In particular, we discuss the initial conditions for Population III star formation, as given by variants of the cold dark matter cosmology. Numerical simulations have investigated the collapse and the fragmentation of metal-free gas, showing that the first stars were predominantly very massive. The exact determination of the stellar masses, and the precise form of the primordial initial mass function, is still hampered by our limited understanding of the accretion physics and the protostellar feedback effects. We address the importance of heavy elements in bringing about the transition from an early star formation mode dominated by massive stars, to the familiar mode dominated by low mass stars, at later times. We show how complementary observations, both at high redshifts and in our local cosmic neighborhood, can be utilized to probe the first epoch of star formation.
849 citations
TL;DR: In this article, the authors considered the deSitter universe and Nariai universe induced by quantum CFT with classical phantom matter and perfect fluid and showed that it is easier to achieve the acceleration of the scale factor preserving the energy conditions in such unified model.
Abstract: We consider deSitter universe and Nariai universe induced by quantum CFT with classical phantom matter and perfect fluid. The model represents the combination of trace-anomaly driven inflation and phantom driven deSitter universe. The similarity of phantom matter with quantum CFT indicates that phantom scalar may be the effective description for some quantum field theory. It is demonstrated that it is easier to achieve the acceleration of the scale factor preserving the energy conditions in such unified model. Some properties of unified theory (anti-gravitating solutions, negative ADM mass Nariai solution, relation with steady state) are briefly mentioned.
831 citations
TL;DR: In this paper, physical motivations, phenomenological consequences, and open problems of the so-called pre-big bang scenario in superstring cosmology are reviewed, as well as some open problems.
803 citations
01 Jan 2003
TL;DR: In this paper, the authors use the Wilkinson Microwave Anisotropy Probe (WMAP) data, in combination with complementary small-scale cosmic microwave background (CMB) measurements and large-scale structure data, to explore the parameter space of inflationary models that is consistent with the WMAP data.
Abstract: We confront predictions of inflationary scenarios with the Wilkinson Microwave Anisotropy Probe (WMAP) data, in combination with complementary small-scale cosmic microwave background (CMB) measurements and large-scale structure data. The WMAP detection of a large-angle anticorrelation in the temperature-polarization cross-power spectrum is the signature of adiabatic superhorizon fluctuations at the time of decoupling. The WMAP data are described by pure adiabatic fluctuations: we place an upper limit on a correlated cold dark matter (CDM) isocurvature component. Using WMAP constraints on the shape of the scalar power spectrum and the amplitude of gravity waves, we explore the parameter space of inflationary models that is consistent with the data. We place limits on inflationary models; for example, a minimally coupled �� 4 is disfavored at more than 3 � using WMAP data in combination with smaller scale CMB and large-scale structure survey data. The limits on the primordial parameters using WMAP data alone are nsðk0 ¼ 0:002 Mpc � 1 Þ¼ 1:20 þ0:12 � 0:11 , dns=d ln k ¼� 0:077 þ0:050 � 0:052 , Aðk0 ¼ 0:002 Mpc � 1 Þ¼ 0:71 þ0:10 � 0:11 (68% CL), and rðk0 ¼ 0:002 Mpc � 1 Þ < 1:28 (95% CL). Subject headings: cosmic microwave background — cosmology: observations — early universe
802 citations
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10 Dec 2003
TL;DR: In this article, an inflationary de Sitter phase is obtained with a ghost condensate and the transition to radiation dominance is triggered by the ghost itself, without any slow-roll potential density perturbations are generated by fluctuations around the ghost and can be reliably computed in the effective field theory.
Abstract: We propose a new scenario for early cosmology, where an inflationary de Sitter phase is obtained with a ghost condensate The transition to radiation dominance is triggered by the ghost itself, without any slow-roll potential Density perturbations are generated by fluctuations around the ghost condensate and can be reliably computed in the effective field theory The fluctuations are scale invariant as a consequence of the de Sitter symmetries, however, the size of the perturbations are parametrically different from conventional slow-roll inflation, and the inflation happens at far lower energy scales The model makes definite predictions that distinguish it from standard inflation, and can be sharply excluded or confirmed by experiments in the near future The tilt in the scalar spectrum is predicted to vanish (n_s=1), and the gravity wave signal is negligible The non-Gaussianities in the spectrum are predicted to be observable: the 3-point function is determined up to an overall order 1 constant, and its magnitude is much bigger than in conventional inflation, with an equivalent f_NL ~ 100, not far from the present WMAP bounds
594 citations
TL;DR: Weak gravitational lensing provides a unique method to map directly the distribution of dark matter in the universe and to measure cosmological parameters as mentioned in this paper, which is a cosmic-shear technique.
Abstract: ▪ Abstract Weak gravitational lensing provides a unique method to map directly the distribution of dark matter in the universe and to measure cosmological parameters. This cosmic-shear technique is...
538 citations
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TL;DR: In this paper, the precise mathematical structure underlying loop quantum cosmology and the sense in which it implements the full quantization program in a symmetry reduced model has been made explicit, thereby providing a firmer mathematical and conceptual foundation to the subject.
Abstract: Applications of Riemannian quantum geometry to cosmology have had notable successes. In particular, the fundamental discreteness underlying quantum geometry has led to a natural resolution of the big bang singularity. However, the precise mathematical structure underlying loop quantum cosmology and the sense in which it implements the full quantization program in a symmetry reduced model has not been made explicit. The purpose of this paper is to address these issues, thereby providing a firmer mathematical and conceptual foundation to the subject.
TL;DR: The MAP mission as mentioned in this paper was designed to determine the geometry, content and evolution of the universe via a 13' full width half-maximum (FWHM) resolution full-sky map of the temperature anisotropy of the cosmic microwave background radiation with uncorrelated pixel noise, minimal systematic errors, multifrequency observations, and accurate calibration.
Abstract: The purpose of the MAP mission is to determine the geometry, content, and evolution of the universe via a 13' full width half-maximum (FWHM) resolution full-sky map of the temperature anisotropy of the cosmic microwave background radiation with uncorrelated pixel noise, minimal systematic errors, multifrequency observations, and accurate calibration. These attributes were key factors in the success of NASA's Cosmic Background Explorer (COBE) mission, which made a 7° FWHM resolution full sky map, discovered temperature anisotropy, and characterized the fluctuations with two parameters, a power spectral index and a primordial amplitude. Following COBE, considerable progress has been made in higher resolution measurements of the temperature anisotropy. With 45 times the sensitivity and 33 times the angular resolution of the COBE mission, MAP will vastly extend our knowledge of cosmology. MAP will measure the physics of the photon-baryon fluid at recombination. From this, MAP measurements will constrain models of structure formation, the geometry of the universe, and inflation. In this paper we present a prelaunch overview of the design and characteristics of the MAP mission. This information will be necessary for a full understanding of the MAP data and results, and will also be of interest to scientists involved in the design of future cosmic microwave background experiments and/or space science missions.
TL;DR: In this article, the emerging standard model of cosmology, a flat Lambda-dominated universe seeded by nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data.
Abstract: WMAP precision data enables accurate testing of cosmological models. We find that the emerging standard model of cosmology, a flat Lambda-dominated universe seeded by nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data. With parameters fixed only by WMAP data, we can fit finer scale CMB measurements and measurements of large scle structure (galaxy surveys and the Lyman alpha forest). This simple model is also consistent with a host of other astronomical measurements. We then fit the model parameters to a combination of WMAP data with other finer scale CMB experiments (ACBAR and CBI), 2dFGRS measurements and Lyman alpha forest data to find the model's best fit cosmological parameters: h=0.71+0.04-0.03, Omega_b h^2=0.0224+-0.0009, Omega_m h^2=0.135+0.008-0.009, tau=0.17+-0.06, n_s(0.05/Mpc)=0.93+-0.03, and sigma_8=0.84+-0.04. WMAP's best determination of tau=0.17+-0.04 arises directly from the TE data and not from this model fit, but they are consistent. These parameters imply that the age of the universe is 13.7+-0.2 Gyr. The data favors but does not require a slowly varying spectral index. By combining WMAP data with other astronomical data sets, we constrain the geometry of the universe, Omega_tot = 1.02 +- 0.02, the equation of state of the dark energy w = -1), and the energy density in stable neutrinos, Omega_nu h^2 < 0.0076 (95% confidence limit). For 3 degenerate neutrino species, this limit implies that their mass is less than 0.23 eV (95% confidence limit). The WMAP detection of early reionization rules out warm dark matter.
TL;DR: A simple geometrical model of a finite space—the Poincaré dodecahedral space—which accounts for WMAP's observations with no fine-tuning required is presented, and the model also predicts temperature correlations in matching circles on the sky.
Abstract: The current ‘standard model’ of cosmology posits an infinite flat universe forever expanding under the pressure of dark energy. First-year data from the Wilkinson Microwave Anisotropy Probe (WMAP) confirm this model to spectacular precision on all but the largest scales1,2. Temperature correlations across the microwave sky match expectations on angular scales narrower than 60° but, contrary to predictions, vanish on scales wider than 60°. Several explanations have been proposed3,4. One natural approach questions the underlying geometry of space—namely, its curvature5 and topology6. In an infinite flat space, waves from the Big Bang would fill the universe on all length scales. The observed lack of temperature correlations on scales beyond 60° means that the broadest waves are missing, perhaps because space itself is not big enough to support them. Here we present a simple geometrical model of a finite space—the Poincare dodecahedral space—which accounts for WMAP's observations with no fine-tuning required. The predicted density is Ω0 ≈ 1.013 > 1, and the model also predicts temperature correlations in matching circles on the sky7.
TL;DR: The MAP mission as discussed by the authors was designed to determine the geometry, content and evolution of the universe via a 13 arcmin full-width-half-max (FWHM) resolution full sky map of the temperature anisotropy of the cosmic microwave background radiation with uncorrelated pixel noise, minimal systematic errors, multifrequency observations, and accurate calibration.
Abstract: The purpose of the MAP mission is to determine the geometry, content, and evolution of the universe via a 13 arcmin full-width-half-max (FWHM) resolution full sky map of the temperature anisotropy of the cosmic microwave background radiation with uncorrelated pixel noise, minimal systematic errors, multifrequency observations, and accurate calibration. These attributes were key factors in the success of NASA's Cosmic Background Explorer (COBE) mission, which made a 7 degree FWHM resolution full sky map, discovered temperature anisotropy, and characterized the fluctuations with two parameters, a power spectral index and a primordial amplitude. Following COBE considerable progress has been made in higher resolution measurements of the temperature anisotropy. With 45 times the sensitivity and 33 times the angular resolution of the COBE mission, MAP will vastly extend our knowledge of cosmology. MAP will measure the physics of the photon-baryon fluid at recombination. From this, MAP measurements will constrain models of structure formation, the geometry of the universe, and inflation. In this paper we present a pre-launch overview of the design and characteristics of the MAP mission. This information will be necessary for a full understanding of the MAP data and results, and will also be of interest to scientists involved in the design of future cosmic microwave background experiments and/or space science missions.
TL;DR: The Cosmic Microwave Background (CMB) anisotropy power on the largest angular scales observed both by WMAP and COBE DMR appears to be lower than the one predicted by the standard model of cosmology with almost scale free primordial perturbations arising from a period of inflation.
Abstract: The Cosmic Microwave Background (CMB) anisotropy power on the largest angular scales observed both by WMAP and COBE DMR appears to be lower than the one predicted by the standard model of cosmology with almost scale free primordial perturbations arising from a period of inflation. One can either interpret this as a manifestation of cosmic variance or as a physical effect that requires an explanation. We discuss various mechanisms that could be responsible for the suppression of such low l multipoles. Features in the late time evolution of metric fluctuations may do this via the integral Sachs–Wolfe effect. Another possibility is a suppression of power at large scales in the primordial spectrum induced by a fast rolling stage in the evolution of the inflaton field at the beginning of the last 65 e-folds of inflation. We illustrate this effect in a simple model of inflation and fit the resulting CMB spectrum to the observed temperature–temperature (TT) power spectrum. We find that the WMAP observations suggest a cutoff at kc = 4.9+1.3−1.6 × 10−4 Mpc−1 at 68% confidence, but only an upper limit of kc < 7.4 × 10−4 Mpc−1 at 95%. Thus, although it improves the fit of the data, the presence of a cutoff in power spectrum is only required at a level close to 2σ. This is obtained with a prior which corresponds to equal distribution w.r.t. kc. We discuss how other choices (such as an equal distribution w.r.t. lnkc, which is natural in the context of inflation) can affect the statistical interpretation.
TL;DR: In this article, it is suggested that current cosmic acceleration arises due to modification of general relativity by the terms with negative powers of curvature, and that such a model which seems to eliminate the need for dark energy may have the origin in M-theory.
28 Nov 2003
TL;DR: In this paper, the authors review the major challenges for high-energy neutrino astrophysics, among which the nature of dark matter, the origin of cosmic rays, and the physics of extreme objects such as active galactic nuclei, gamma-ray bursts, pulsars, and supernova remnants are of prime importance.
Abstract: ▪ Abstract High-energy (>100 MeV) neutrino astrophysics enters an era of opportunity and discovery as the sensitivity of detectors approaches astrophysically relevant flux levels. We review the major challenges for this emerging field, among which the nature of dark matter, the origin of cosmic rays, and the physics of extreme objects such as active galactic nuclei, gamma-ray bursts, pulsars, and supernova remnants are of prime importance. Variable sources at cosmological distances allow the probing of neutrino propagation properties over baselines up to about 20 orders of magnitude larger than those probed by terrestrial long-baseline experiments. We review the possible astrophysical sources of high-energy neutrinos, which also act as an irreducible background to searches for phenomena at the electroweak and grand-unified-theory symmetry-breaking scales related to possible supersymmetric dark matter and topological defects. Neutrino astronomy also has the potential to discover previously unimagined high-...
Book•
31 Oct 2003
TL;DR: In this paper, the authors discuss cosmological models as dynamical systems, with particular emphasis on applications in the early universe and point out the important role of self-similar models.
Abstract: Dynamical systems theory is especially well-suited for determining the possible asymptotic states (at both early and late times) of cosmological models, particularly when the governing equations are a finite system of autonomous ordinary differential equations In this book we discuss cosmological models as dynamical systems, with particular emphasis on applications in the early Universe We point out the important role of self-similar models We review the asymptotic properties of spatially homogeneous perfect fluid models in general relativity We then discuss results concerning scalar field models with an exponential potential (both with and without barotropic matter) Finally, we discuss the dynamical properties of cosmological models derived from the string effective action This book is a valuable source for all graduate students and professional astronomers who are interested in modern developments in cosmology
01 Jan 2003
TL;DR: In this paper, a detailed study of cosmological effects of homogeneous tachyon matter coexisting with nonrelativistic matter and radiation is presented, focusing on the inverse square potential and the exponential potential for the tachyonic scalar field.
Abstract: We present a detailed study of cosmological effects of homogeneous tachyon matter coexisting with nonrelativistic matter and radiation, concentrating on the inverse square potential and the exponential potential for the tachyonic scalar field. A distinguishing feature of these models (compared to other cosmological models) is that the matter density parameter and the density parameter for tachyons remain comparable even in the matter dominated phase. For the exponential potential, the solutions have an accelerating phase, followed by a phase with a(t)∝t ⅔ as t∝∞. This eliminates the future event horizon present in cold dark matter models with a cosmological constant (ΛCDM) and is an attractive feature from the string theory perspective. A comparison with supernova type Ia data shows that for both the potentials there exists a range of models in which the universe undergoes an accelerated expansion at low redshifts which are also consistent with the requirements of structure formation. They do require fine-tuning of parameters but not any more than in the case of ΛCDM models or quintessence models.
TL;DR: In this article, it was shown that even if the precise value of w X is known from observations, it is not possible to determine the nature of the unknown dark energy source using only kinematical and geometrical measurements.
Abstract: Current cosmological observations show a strong signature of the existence of a dark energy component with negative pressure. The most obvious candidate for this dark energy is the cosmological constant (with the equationof state w X = p/ρ = -1), which, however, raises several theoretical difficulties. This has led to models for a dark energy component that evolves with time. We discuss certain questions related to the determination of the nature of the dark energy component from observations of high-redshift supernovae. The main results of our analysis are as follows. (i) Even if the precise value of w X is known from observations, it is not possible to determine the nature of the unknown dark energy source using only kinematical and geometrical measurements. We have given explicit examples to show that different types of sources can give rise to a given w X . (ii) Although the full data set of supernova observations (which are currently available) strongly rule out models without dark energy, the high- (z > 0.25) and low- (z < 0.25) redshift data sets, individually, admit decelerating models with zero dark energy. Any possible evolution in the absolute magnitude of the supernovae, if detected, might allow the decelerating models to be consistent with the data. (iii) We have introduced two parameters, which can be obtained entirely from theory, to study the sensitivity of the luminosity distance on w X . Using these two parameters, we have argued that although one can determine the present value of w X accurately from the data, one cannot constrain the evolution of w X .
TL;DR: In this paper, the authors present analytical estimates as well as one-dimensional radiation hydrodynamical calculations of the evolution of these first HII regions in the universe, and find that most of the gas surrounding the first stars will leave the dark halo whether or not the stars produce supernovae.
Abstract: We simulate the ionization environment of z ~ 20 luminous objects formed within the framework of the current CDM cosmology and compute their UV escape fraction. These objects are likely single very massive stars that are copious UV emitters. We present analytical estimates as well as one--dimensional radiation hydrodynamical calculations of the evolution of these first HII regions in the universe. The initially D--type ionization front evolves to become R--type within $\lesssim 10^5$ yrs at a distance $\sim1$ pc. This ionization front then completely overruns the halo, accelerating an expanding shell of gas outward to velocities in excess of 30 km s$^{-1}$, about ten times the escape velocity of the confining dark matter halo. We find that the evolution of the HII region depends only weakly on the assumed stellar ionizing luminosities. Consequently, most of the gas surrounding the first stars will leave the dark halo whether or not the stars produce supernovae. If they form the first massive seed black holes these are unlikely to accrete within a Hubble time after they formed until they are incorporated into larger dark matter halos that contain more gas. Because these I--fronts exit the halo on timescales much shorter than the stars' main sequence lifetimes their host halos have UV escape fractions of $\gtrsim 0.95$, fixing an important parameter for theoretical studies of cosmological hydrogen reionization.
TL;DR: In this article, the authors compared the results from the Wilkinson Microwave Anisotropic Probe (WMAP) and the CMB baryometer with the current state of BBN theory and light element observations, including their possible lingering systematic errors.
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TL;DR: In this paper, the authors discuss a class of phantom cosmological models and discuss the problem of singularities for these cosmologies, and find an interesting relation between the phantom models and standard matter models which is like the duality symmetry of string cosmology.
Abstract: We discuss a class of phantom ($p < - \varrho$) cosmological models Except for phantom we admit various forms of standard types of matter and discuss the problem of singularities for these cosmologies The singularities are different from those of standard matter cosmology since they appear for infinite values of the scale factor We also find an interesting relation between the phantom models and standard matter models which is like the duality symmetry of string cosmology
TL;DR: In this article, the authors assess a scenario where the universe was reionized by ''miniquasars'' powered by intermediate-mass black holes (IMBHs), the remnants of the first generation of massive stars.
Abstract: Motivated by the recent detection by WMAP of a large optical depth to Thomson scattering -- implying a very early reionization epoch -- we assess a scenario where the universe was reionized by `miniquasars' powered by intermediate-mass black holes (IMBHs), the remnants of the first generation of massive stars. Pregalactic IMBHs form within minihalos above the cosmological Jeans mass collapsing at z=24, get incorporated through mergers into larger and larger systems, sink to the center owing to dynamical friction, and accrete cold material. The merger history of dark halos and associated IMBHs is followed by Monte Carlo realizations of the merger hierarchy in a LCDM cosmology. While seed IMBHs that are as rare as the 3.5-sigma peaks of the primordial density field evolve largely in isolation, a significant number of black hole binary systems will form if IMBHs populate the more numerous 3-sigma peaks instead. In the case of rapid binary coalescence a fraction of IMBHs will be displaced from galaxy centers and ejected into the IGM by the `gravitational rocket' effect, rather than accrete and shine as miniquasars. We show that, under a number of plausible assumptions for the amount of gas accreted onto IMBHs and their emission spectrum, miniquasars powered by IMBHs may be responsible for cosmological reionization at z~15. Reionization by miniquasars with a hard spectrum may be more `economical' than stellar reionization, as soft X-rays escape more easily from the dense sites of star formation and travel further than EUV radiation. Energetic photons will make the diffuse IGM warm and weakly ionized prior to the epoch of reionization breakthrough, set an entropy floor, and reduce gas clumping. Future 21 cm observations may detect a preheated, weakly-ionized IGM in emission against the CMB. (abridged)
01 Jan 2003
TL;DR: The second edition of the Introduction to Cosmology as discussed by the authors is an exciting update of an award-winning textbook aimed primarily at advanced undergraduate students in physics and astronomy, but is also useful as a supplementary text at higher levels.
Abstract: This second edition of Introduction to Cosmology is an exciting update of an award-winning textbook. It is aimed primarily at advanced undergraduate students in physics and astronomy, but is also useful as a supplementary text at higher levels. It explains modern cosmological concepts, such as dark energy, in the context of the Big Bang theory. Its clear, lucid writing style, with a wealth of useful everyday analogies, makes it exceptionally engaging. Emphasis is placed on the links between theoretical concepts of cosmology and the observable properties of the universe, building deeper physical insights in the reader. The second edition includes recent observational results, fuller descriptions of special and general relativity, expanded discussions of dark energy, and a new chapter on baryonic matter that makes up stars and galaxies. It is an ideal textbook for the era of precision cosmology in the accelerating universe.
TL;DR: In this paper, a model consisting of tachyon which may have the negative kinetic energy plus scalar phantom and plus conformal quantum matter was discussed, and it was demonstrated that such a model naturally admits two de Sitter phases where the early universe inflation is produced by quantum effects and the late time accelerating universe is caused by phantom/tachyon.
TL;DR: In this article, the authors investigate tachyon dynamics with an inverse power-law potential V (φ)∝φ−α and find global attractors of the dynamics leading to a dust behavior for α > 2 and to an accellerating universe for 0 <α≤ 2.
Pennsylvania State University1, University of Arizona2, Princeton University3, Fermilab4, Adler Planetarium5, University of Chicago6, University of Pittsburgh7, University of Washington8, Microsoft9, Max Planck Society10, New York University11, Apache Corporation12, California Institute of Technology13, Massachusetts Institute of Technology14, Spanish National Research Council15, University of Tokyo16, Johns Hopkins University17, Lawrence Berkeley National Laboratory18, University of Sussex19, Space Telescope Science Institute20, University of Edinburgh21, Rensselaer Polytechnic Institute22, Rochester Institute of Technology23
TL;DR: The second edition of the Sloan Digital Sky Survey (SDSS) Quasar catalog as mentioned in this paper consists of the 16,713 objects in the SDSS First Data Release that have luminosities larger than Mi = -22.
Abstract: We present the second edition of the Sloan Digital Sky Survey (SDSS) Quasar Catalog. The catalog consists of the 16,713 objects in the SDSS First Data Release that have luminosities larger than Mi = -22 (in a cosmology with H0 = 70 km s-1 Mpc-1, ΩM = 0.3, and ΩΛ = 0.7), have at least one emission line with FWHM larger than 1000 km s-1, and have highly reliable redshifts. The area covered by the catalog is ≈1360 deg2. The quasar redshifts range from 0.08 to 5.41, with a median value of 1.43. For each object, the catalog presents positions accurate to better than 02 rms per coordinate, five-band (ugriz) CCD-based photometry with typical accuracy of 0.03 mag, and information on the morphology and selection method. The catalog also contains some radio, near-infrared, and X-ray emission properties of the quasars, when available, from other large-area surveys. Calibrated digital spectra of all objects in the catalog, covering the wavelength region 3800–9200 A at a spectral resolution of 1800–2100, are available. This publication supersedes the first SDSS Quasar Catalog, which was based on material from the SDSS Early Data Release. A summary of corrections to current quasar databases is also provided. The majority of the objects were found in SDSS commissioning data using a multicolor selection technique. Since the quasar selection algorithm was undergoing testing during the entire observational period covered by this catalog, care must be taken when assembling samples from the catalog for use in statistical studies. A total of 15,786 objects (94%) in the catalog were discovered by the SDSS; 12,173 of the SDSS discoveries are reported here for the first time. Included in the new discoveries are five quasars brighter than i = 16.0 and 17 quasars with redshifts larger than 4.5.
TL;DR: A review of black hole and brane production in TeV-scale gravity is presented in this article, where the formation and subsequent decay of these super-Planckian objects would be detectable in particle colliders and high energy cosmic ray detectors, and have interesting implications in cosmology and astrophysics.
Abstract: In models with large extra dimensions, particle collisions with center-of-mass energy larger than the fundamental gravitational scale can generate nonperturbative gravitational objects such as black holes and branes. The formation and the subsequent decay of these super-Planckian objects would be detectable in particle colliders and high energy cosmic ray detectors, and have interesting implications in cosmology and astrophysics. In this paper we present a review of black hole and brane production in TeV-scale gravity.