Journal ArticleDOI
Evidence for a positive cosmological constant from flows of galaxies and distant supernovae
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TLDR
In this article, an independent constraint on the lower bound to the mass density was derived based on deviations of galaxy velocities from a smooth universal expansion, and together with a nearly flat universe in which the contributions from mass density and the cosmological constant are comparable.Abstract:
Recent observations1,2 of high-redshift supernovae seem to suggest that the global geometry of the Universe may be affected by a ‘cosmological constant’, which acts to accelerate the expansion rate with time. But these data by themselves still permit an open universe of low mass density and no cosmological constant. Here we derive an independent constraint on the lower bound to the mass density, based on deviations of galaxy velocities from a smooth universal expansion3,4,5,6,7. This constraint rules out a low-density open universe with a vanishing cosmological constant, and together the two favour a nearly flat universe in which the contributions from mass density and the cosmological constant are comparable. This type of universe, however, seems to require a degree of fine tuning of the initial conditions that is in apparent conflict with ‘common wisdom’.read more
Citations
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Journal ArticleDOI
The Case for a Positive Cosmological Λ-Term
TL;DR: In this article, the authors review both observational and theoretical aspects of a small cosmological Λ-term and discuss the current observational situation focusing on cosmology tests of Λ including the age of the universe, high redshift supernovae, gravitational lensing, galaxy clustering and the cosmic microwave background.
Existential risks: analyzing human extinction scenarios and related hazards
TL;DR: This paper analyzes a recently emerging category: that of existential risks, threats that could case the authors' extinction or destroy the potential of Earth - originating intelligent life.
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Dark matter and background light
James Overduin,Paul S. Wesson +1 more
TL;DR: In this article, the authors review what is known about dark matter and energy from their impact on the light of the night sky and conclude that the dark matter is most likely to be WIMPs if conventional cosmology holds; or higher-dimensional sources if spacetime needs to be extended.
Journal ArticleDOI
Current Cosmological Constraints from a 10 Parameter Cosmic Microwave Background Analysis
Max Tegmark,Matias Zaldarriaga +1 more
TL;DR: In this article, the authors compute the constraints on a "standard" 10 parameter cold dark matter (CDM) model from the most recent CMB data and other observations, exploring 30 million discrete models and two continuous parameters.
Journal ArticleDOI
Experimental constraints on the axion dark matter halo density
S.J. Asztalos,E. J. Daw,H. Peng,L.J. Rosenberg,D. B. Yu,C. A. Hagmann,Darin Kinion,Wolfgang Stoeffl,K. van Bibber,J. LaVeigne,Pierre Sikivie,Neil Sullivan,David B. Tanner,F. A. Nezrick,D. M. Moltz +14 more
TL;DR: In this article, a search that probes the local Galactic halo axion density using the Sikivie radio frequency cavity technique was carried out and it was shown that axions of Kim and Shifman, Vainshtein, and Zakharov contribute no more than 0.45 GeV cm 3 of mass density to the local dark matter halo over this mass range.
References
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Journal ArticleDOI
Measurements of Omega and Lambda from 42 High-Redshift Supernovae
Saul Perlmutter,Saul Perlmutter,Greg Aldering,Gerson Goldhaber,Gerson Goldhaber,R. A. Knop,Peter Nugent,P. G. Castro,P. G. Castro,Susana E. Deustua,Sebastien Fabbro,Sebastien Fabbro,A. Goobar,A. Goobar,Donald E. Groom,I. M. Hook,I. M. Hook,A. G. Kim,A. G. Kim,A. G. Kim,M. Y. Kim,Julia C. Lee,Julia C. Lee,Nelson J. Nunes,Nelson J. Nunes,Reynald Pain,Reynald Pain,C. R. Pennypacker,C. R. Pennypacker,Robert Quimby,Christopher Lidman,Richard S. Ellis,Mike Irwin,Richard G. McMahon,Pilar Ruiz-Lapuente,Nicholas A. Walton,Bradley E. Schaefer,B. J. Boyle,Alexei V. Filippenko,Thomas Matheson,A. S. Fruchter,Nino Panagia,Nino Panagia,Heidi Jo Newberg,Warrick J. Couch +44 more
TL;DR: In this paper, the mass density, Omega_M, and cosmological-constant energy density of the universe were measured using the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology project.
Journal ArticleDOI
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
Adam G. Riess,Alexei V. Filippenko,Peter Challis,Alejandro Clocchiatti,Alan H. Diercks,Peter M. Garnavich,R. L. Gilliland,Craig J. Hogan,Saurabh Jha,Robert P. Kirshner,Bruno Leibundgut,Mark M. Phillips,David J Reiss,Brian P. Schmidt,R. A. Schommer,R. Chris Smith,R. Chris Smith,Jason Spyromilio,Christopher W. Stubbs,Nicholas B. Suntzeff,John L. Tonry +20 more
TL;DR: In this article, the authors used spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 " z " 0.62.
Journal ArticleDOI
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
Adam G. Riess,Alexei V. Filippenko,Peter Challis,Alejandro Clocchiattia,Alan H. Diercks,Peter M. Garnavich,R. L. Gilliland,Craig J. Hogan,Saurabh Jha,Robert P. Kirshner,Bruno Leibundgut,Mark M. Phillips,David J Reiss,Brian P. Schmidt,Robert A. Schommer,R. Chris Smith,Jason Spyromilio,Christopher W. Stubbs,Nicholas B. Suntzeff,John L. Tonry +19 more
TL;DR: In this paper, the authors present observations of 10 type Ia supernovae (SNe Ia) between 0.16 0 and 4.0 sigma confidence levels, for two fitting methods respectively.
Journal ArticleDOI
Measurements of Omega and Lambda from 42 High-Redshift Supernovae
Saul Perlmutter,Greg Aldering,G. Goldhaber,R. A. Knop,Peter Nugent,P. G. Castro,Susana E. Deustua,Sebastien Fabbro,A. Goobar,D. E. Groom,I. M. Hook,A. G. Kim,M. Y. Kim,Julia C. Lee,Nelson J. Nunes,Reynald Pain,C. R. Pennypacker,R. M. Quimby,C. Lidman,Richard S. Ellis,Michael G. Irwin,Richard G. McMahon,P. Ruiz-Lapuente,Nicholas A. Walton,Bradley E. Schaefer,B. J. Boyle,Alexei V. Filippenko,Thomas Matheson,A. S. Fruchter,Nino Panagia,Heidi Jo Newberg,W. J. Couch +31 more
TL;DR: In this paper, the mass density, Omega_M, and cosmological-constant energy density of the universe were measured by the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology Project.
Journal ArticleDOI
The Cosmological Constant Problem
TL;DR: In this article, five different approaches to the cosmological constant problem are described, and a brief review of the history of this problem is given. But none of the approaches are considered in this paper.
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