Dark matter and dark energy
Varun Sahni
- 13 Mar 2004
Vol. 653, pp 141-180
TL;DR: A review of the current understanding of dark matter and dark en- ergy can be found in this paper, where the authors discuss the significance of the cosmological constant problem, current constraints and the 'abundance of substructure' and 'cuspy core' issues which arise in CDM.
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Abstract: I briefly review our current understanding of dark matter and dark en- ergy. The first part of this paper focusses on issues pertaining to dark matter includ- ing observational evidence for its existence, current constraints and the 'abundance of substructure' and 'cuspy core' issues which arise in CDM. I also briefly describe MOND. The second part of this review focusses on dark energy. In this part I dis- cuss the significance of the cosmological constant problem which leads to a predicted value of the cosmological constant which is almost 10 123 times larger than the ob- served value �/8�G ≃ 10 47 GeV 4 . Settingto this small value ensures that the acceleration of the universe is a fairly recent phenomenon giving rise to the 'cosmic coincidence' conundrum according to which we live during a special epoch when the density in matter andare almost equal. Anthropic arguments are briefly dis- cussed but more emphasis is placed upon dynamical dark energy models in which the equation of state is time dependent. These include Quintessence, Braneworld models, Chaplygin gas and Phantom energy. Model independent methods to deter- mine the cosmic equation of state and the Statefinder diagnostic are also discussed. The Statefinder has the attractive property ... a /aH 3 = 1 for LCDM, which is helpful for differentiating between LCDM and rival dark energy models. The review ends with a brief discussion of the fate of the universe in dark energy models.
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Figures
Table 1. ![Fig. 10. The time evolution of the statefinder pair {r, s} for quintessence models and the Chaplygin gas. Solid lines to the right of LCDM represent tracker potentials V = V0/φ α, while those to the left correspond to the Chaplygin gas. Dot-dashed lines represent DE with a constant equation of state w. Tracker models tend to approach the LCDM fixed point (r = 1, s = 0) from the right at t → ∞, whereas the Chaplygin gas approaches LCDM from the left. For Chaplygin gas κ is the ratio between matter density and the density of the Chaplygin gas at early times. The dashed curve in the lower right is the envelope of all quintessence models, while the dashed curve in the upper left is the envelope of Chaplygin gas models (the latter is described by κ = Ωm/1−Ωm). The region outside the dashed curves is forbidden for both classes of dark energy models. The ability of the Statefinder to differentiate between dark energy models is clearly demonstrated. From Alam, Sahni, Saini and Starobinsky [2].](/figures/figure10-1-6ne5updx298r.png)
Fig. 10. The time evolution of the statefinder pair {r, s} for quintessence models and the Chaplygin gas. Solid lines to the right of LCDM represent tracker potentials V = V0/φ α, while those to the left correspond to the Chaplygin gas. Dot-dashed lines represent DE with a constant equation of state w. Tracker models tend to approach the LCDM fixed point (r = 1, s = 0) from the right at t → ∞, whereas the Chaplygin gas approaches LCDM from the left. For Chaplygin gas κ is the ratio between matter density and the density of the Chaplygin gas at early times. The dashed curve in the lower right is the envelope of all quintessence models, while the dashed curve in the upper left is the envelope of Chaplygin gas models (the latter is described by κ = Ωm/1−Ωm). The region outside the dashed curves is forbidden for both classes of dark energy models. The ability of the Statefinder to differentiate between dark energy models is clearly demonstrated. From Alam, Sahni, Saini and Starobinsky [2]. ![Fig. 2. The power spectrum inferred from observations of large scale structure, the Lymanα forest, gravitational lensing and the CMB. The solid line shows the power spectrum prediction for a flat scale-invariant LCDM model with Ωm = 0.28, Ωb/Ωm = 0.16, h = 0.72; from Tegmark et al. [201].](/figures/figure2-1-1i8d57h30qfc.png)
Fig. 2. The power spectrum inferred from observations of large scale structure, the Lymanα forest, gravitational lensing and the CMB. The solid line shows the power spectrum prediction for a flat scale-invariant LCDM model with Ωm = 0.28, Ωb/Ωm = 0.16, h = 0.72; from Tegmark et al. [201]. ![Fig. 9. The relative difference between the Hubble parameter reconstructed from SNe data and the LCDM value is shown as a function of redshift. SNe data from Tonry et al (2003) were used for the reconstruction. The best-fit is represented by the thick solid line assuming Ωm = 0.3. The light (dark) grey contours represents the 1σ (2σ) confidence levels around the best-fit. The dashed horizontal line shows LCDM. From Alam, Sahni, Saini and Starobinsky [4].](/figures/figure9-1-1fa4sv37f2xh.png)
Fig. 9. The relative difference between the Hubble parameter reconstructed from SNe data and the LCDM value is shown as a function of redshift. SNe data from Tonry et al (2003) were used for the reconstruction. The best-fit is represented by the thick solid line assuming Ωm = 0.3. The light (dark) grey contours represents the 1σ (2σ) confidence levels around the best-fit. The dashed horizontal line shows LCDM. From Alam, Sahni, Saini and Starobinsky [4]. ![Fig. 11. Target statistical uncertainty of the SNe experiment is shown overlaid with current results from CMB and LSS observations. From Aldering [11].](/figures/figure11-1-4mh7uvu9v5ac.png)
Fig. 11. Target statistical uncertainty of the SNe experiment is shown overlaid with current results from CMB and LSS observations. From Aldering [11]. 
Fig. 4. Spontaneous symetry breaking in many field theory models takes the form of the Mexican top hat potential shown above. The dashed line shows the potential before the cosmological constant has been ‘renormalized’ and the solid line after. (From Sahni and Starobinsky 2000.)
![Fig. 10. The time evolution of the statefinder pair {r, s} for quintessence models and the Chaplygin gas. Solid lines to the right of LCDM represent tracker potentials V = V0/φ α, while those to the left correspond to the Chaplygin gas. Dot-dashed lines represent DE with a constant equation of state w. Tracker models tend to approach the LCDM fixed point (r = 1, s = 0) from the right at t → ∞, whereas the Chaplygin gas approaches LCDM from the left. For Chaplygin gas κ is the ratio between matter density and the density of the Chaplygin gas at early times. The dashed curve in the lower right is the envelope of all quintessence models, while the dashed curve in the upper left is the envelope of Chaplygin gas models (the latter is described by κ = Ωm/1−Ωm). The region outside the dashed curves is forbidden for both classes of dark energy models. The ability of the Statefinder to differentiate between dark energy models is clearly demonstrated. From Alam, Sahni, Saini and Starobinsky [2].](/figures/figure10-1-6ne5updx298r.webp)
![Fig. 2. The power spectrum inferred from observations of large scale structure, the Lymanα forest, gravitational lensing and the CMB. The solid line shows the power spectrum prediction for a flat scale-invariant LCDM model with Ωm = 0.28, Ωb/Ωm = 0.16, h = 0.72; from Tegmark et al. [201].](/figures/figure2-1-1i8d57h30qfc.webp)
![Fig. 9. The relative difference between the Hubble parameter reconstructed from SNe data and the LCDM value is shown as a function of redshift. SNe data from Tonry et al (2003) were used for the reconstruction. The best-fit is represented by the thick solid line assuming Ωm = 0.3. The light (dark) grey contours represents the 1σ (2σ) confidence levels around the best-fit. The dashed horizontal line shows LCDM. From Alam, Sahni, Saini and Starobinsky [4].](/figures/figure9-1-1fa4sv37f2xh.webp)
![Fig. 11. Target statistical uncertainty of the SNe experiment is shown overlaid with current results from CMB and LSS observations. From Aldering [11].](/figures/figure11-1-4mh7uvu9v5ac.webp)
Citations
Reconstructing the interaction rate in holographic models of dark energy
Anjan A. Sen,Diego Pavón +1 more
TL;DR: Zimdahl and Pavon as mentioned in this paper reconstructed the interaction rate of the holographic dark energy model with observational data from supernovae type Ia, baryon acoustic oscillations, gas mass fraction in galaxy clusters, and the growth factor.
Exact cosmological solution of a scalar-tensor gravity theory compatible with the {Lambda}CDM model
TL;DR: In this article, the authors considered the massive scalar-tensor theory in the Jordan frame and reduced the equations of motion to a system of two differential equations of first order which can be exactly solved.
Thermodynamics in Kaluza-Klein Universe
Muhammad Sharif,Rabia Saleem +1 more
TL;DR: In this article, the validity of the first and generalized second laws of thermodynamics for Kaluza-Klein universe in the state of thermal equilibrium, composed of dark matter and dark energy, were investigated.
Crossing the phantom divide line in the Chaplygin gas model
TL;DR: In this paper, the role of the interaction in reaching and crossing the phantom divide line in the Chaplygin gas model is discussed, and necessary properties of interaction that allow the model to arrive at or cross the phantom Divide line are obtained.
Logarithm of the scale factor as a generalised coordinate in a Lagrangian for dark matter and dark energy
TL;DR: In this paper, a Lagrangian for the k-essence field is set up with canonical kinetic terms and incorporating the scaling relation of [RJ Scherrer, Phys Rev Lett 93 (2004) 011301].
References
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.
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.
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.
A Universal Density Profile from Hierarchical Clustering
TL;DR: In this article, the authors used high-resolution N-body simulations to study the equilibrium density profiles of dark matter halos in hierarchically clustering universes, and they found that all such profiles have the same shape, independent of the halo mass, the initial density fluctuation spectrum, and the values of the cosmological parameters.
10.3K
An Alternative to compactification
TL;DR: In this paper, a single 3-brane embedded in five dimensions was shown to reproduce four-dimensional Newtonian and general relativistic gravity to more than adequate precision, even without a gap in the Kaluza-Klein spectrum.
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