Title:
The cosmological constant problem
Authors:
Weinberg, Steven
Affiliation:
AA(Theory Group, Department of Physics, University of Texas, Austin, Texas 78712)
Publication:
Reviews of Modern Physics, Volume 61, Issue 1, January 1989, pp.1-23 (RvMP Homepage)
Publication Date:
01/1989
Origin:
AIP; APS ttp://www.aip.org ttp://www.aps.org
DOI:
10.1103/RevModPhys.61.1
Bibliographic Code:
1989RvMP...61....1W

Abstract

Astronomical observations indicate that the cosmological constant is many orders of magnitude smaller than estimated in modern theories of elementary particles. After a brief review of the history of this problem, five different approaches to its solution are described.

Title:
The cosmological constant and dark energy
Authors:
Peebles, P. J.; Ratra, Bharat
Affiliation:
AA(Joseph Henry Laboratories, Princeton University, Princeton, New Jersey 08544), AB(Department of Physics, Kansas State University, Manhattan, Kansas 66506)
Publication:
Reviews of Modern Physics, vol. 75, Issue 2, pp. 559-606 (RvMP Homepage)
Publication Date:
04/2003
Origin:
APS
DOI:
10.1103/RevModPhys.75.559
Bibliographic Code:
2003RvMP...75..559P

Abstract

Physics welcomes the idea that space contains energy whose gravitational effect approximates that of Einstein’s cosmological constant, Λ; today the concept is termed dark energy or quintessence. Physics also suggests that dark energy could be dynamical, allowing for the arguably appealing picture of an evolving dark-energy density approaching its natural value, zero, and small now because the expanding universe is old. This would alleviate the classical problem of the curious energy scale of a millielectron volt associated with a constant Λ. Dark energy may have been detected by recent cosmological tests. These tests make a good scientific case for the context, in the relativistic Friedmann-Lemaître model, in which the gravitational inverse-square law is applied to the scales of cosmology. We have well-checked evidence that the mean mass density is not much more than one-quarter of the critical Einstein de Sitter value. The case for detection of dark energy is not yet as convincing but still serious; we await more data, which may be derived from work in progress. Planned observations may detect the evolution of the dark-energy density; a positive result would be a considerable stimulus for attempts at understanding the microphysics of dark energy. This review presents the basic physics and astronomy of the subject, reviews the history of ideas, assesses the state of the observational evidence, and comments on recent developments in the search for a fundamental theory.

Title:
Cosmological constant-the weight of the vacuum
Authors:
Padmanabhan, T.
Affiliation:
AA(IUCAA, Pune University Campus, Ganeshkhind, 411007, Pune, India)
Publication:
Physics Reports, Volume 380, Issue 5-6, p. 235-320.
Publication Date:
07/2003
Origin:
ELSEVIER
DOI:
10.1016/S0370-1573(03)00120-0
Bibliographic Code:
2003PhR...380..235P

Abstract

Recent cosmological observations suggest the existence of a positive cosmological constant /Λ with the magnitude Λ(G planckv/c3)~10-123. This review discusses several aspects of the cosmological constant both from the cosmological (Sections 1-6) and field theoretical (Sections 7-11) perspectives. After a brief introduction to the key issues related to cosmological constant and a historical overview, a summary of the kinematics and dynamics of the standard Friedmann model of the universe is provided. The observational evidence for cosmological constant, especially from the supernova results, and the constraints from the age of the universe, structure formation, Cosmic Microwave Background Radiation (CMBR) anisotropies and a few others are described in detail, followed by a discussion of the theoretical models (quintessence, tachyonic scalar field, /...) from different perspectives. The latter part of the review (Sections 7-11) concentrates on more conceptual and fundamental aspects of the cosmological constant like some alternative interpretations of the cosmological constant, relaxation mechanisms to reduce the cosmological constant to the currently observed value, the geometrical structure of the de Sitter spacetime, thermodynamics of the de Sitter universe and the role of string theory in the cosmological constant problem.

Title:
The cosmological constant
Authors:
Carroll, Sean M.; Press, William H.; Turner, Edwin L.
Affiliation:
AA(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AB(Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), AC(Princeton Univ. Observatory, NJ)
Publication:
In: Annual review of astronomy and astrophysics. Vol. 30 (A93-25826 09-90), p. 499-542. (Annual Reviews Homepage)
Publication Date:
00/1992
Category:
Astrophysics
Origin:
STI
NASA/STI Keywords:
COSMOLOGY, GRAVITATIONAL LENSES, HUBBLE CONSTANT, RELATIVISTIC THEORY, COMPUTATIONAL ASTROPHYSICS, GRAVITATIONAL FIELDS, UNIVERSE
DOI:
10.1146/annurev.aa.30.090192.002435
Bibliographic Code:
1992ARA&A..30..499C

Abstract

The cosmological constant problem is examined in the context of both astronomy and physics. Effects of a nonzero cosmological constant are discussed with reference to expansion dynamics, the age of the universe, distance measures, comoving density of objects, growth of linear perturbations, and gravitational lens probabilities. The observational status of the cosmological constant is reviewed, with attention given to the existence of high-redshift objects, age derivation from globular clusters and cosmic nuclear data, dynamical tests of OmegaLambda, quasar absorption line statistics, gravitational lensing, and astrophysics of distant objects. Finally, possible solutions to the physicist's cosmological constant problem are examined.

Title:
Dynamics of Dark Energy
Authors:
Copeland, Edmund J.; Sami, M.; Tsujikawa, Shinji
Affiliation:
AA(School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7, 2RD, , UK; ), AB(Centre for Theoretical Physics, Jamia Millia Islamia, New Delhi, , India; ), AC(Department of Physics, Gunma National College of Technology, Gunma 371-8530, , Japan; )
Publication:
International Journal of Modern Physics D, Volume 15, Issue 11, pp. 1753-1935 (2006). (IJMPD Homepage)
Publication Date:
00/2006
Origin:
WSPC
Keywords:
Dark energy, cosmological constant, scalar fields, particle physics, modified gravity
DOI:
10.1142/S021827180600942X
Bibliographic Code:
2006IJMPD..15.1753C

Abstract

We review in detail a number of approaches that have been adopted to try and explain the remarkable observation of our accelerating universe. In particular we discuss the arguments for and recent progress made towards understanding the nature of dark energy. We review the observational evidence for the current accelerated expansion of the universe and present a number of dark energy models in addition to the conventional cosmological constant, paying particular attention to scalar field models such as quintessence, K-essence, tachyon, phantom and dilatonic models. The importance of cosmological scaling solutions is emphasized when studying the dynamical system of scalar fields including coupled dark energy. We study the evolution of cosmological perturbations allowing us to confront them with the observation of the Cosmic Microwave Background and Large Scale Structure and demonstrate how it is possible in principle to reconstruct the equation of state of dark energy by also using Supernovae Ia observational data. We also discuss in detail the nature of tracking solutions in cosmology, particle physics and braneworld models of dark energy, the nature of possible future singularities, the effect of higher order curvature terms to avoid a Big Rip singularity, and approaches to modifying gravity which leads to a late-time accelerated expansion without recourse to a new form of dark energy.

Title:
The Cosmological Constant
Authors:
Carroll, Sean M.
Affiliation:
AA(Enrico Fermi Institute and Department of Physics, University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637, U.S.A.)
Publication:
Living Reviews in Relativity
Publication Date:
02/2001
Origin:
LRR; Physical Cosmology
Keywords:
cosmology, cosmological constant, vacuum energy
Bibliographic Code:
2001LRR.....4....1C

Abstract

This is a review of the physics and cosmology of the cosmological constant. Focusing on recent developments, I present a pedagogical overview of cosmology in the presence of a cosmological constant, observational constraints on its magnitude, and the physics of a small (and potentially nonzero) vacuum energy.

Title:
Probing dark energy: Methods and strategies
Authors:
Huterer, Dragan; Turner, Michael S.
Affiliation:
AA(Department of Physics, Enrico Fermi Institute, The University of Chicago, Chicago, Illinois 60637-1433), AB(Department of Physics, Enrico Fermi Institute, The University of Chicago, Chicago, Illinois 60637-1433,)
Publication:
Physical Review D (Particles, Fields, Gravitation, and Cosmology), Volume 64, Issue 12, 15 December 2001, p.123527 (PhRvD Homepage)
Publication Date:
12/2001
Origin:
APS
DOI:
10.1103/PhysRevD.64.123527
Bibliographic Code:
2001PhRvD..64l3527H

Abstract

The presence of dark energy in the Universe is inferred directly from the accelerated expansion of the Universe, and, indirectly, from measurements of cosmic microwave background (CMB) anisotropy. Dark energy contributes about two-thirds of the critical density, is smoothly distributed, has large negative pressure, and is very mysterious. For now, all of its discernible cosmological consequences follow from its effect on the expansion rate of the Universe. Absent a compelling theoretical model (or even a class of models), we describe the dark energy by its equation of state w=pX/ρX which is allowed to vary with time. We describe and compare different approaches for determining w(t), including a magnitude-redshift (Hubble) diagram, number counts of galaxies and clusters, and CMB anisotropy. We focus particular attention on the use of a sample of several thousand type Ia supernova with redshifts z<~1.7, as might be gathered by the proposed SNAP satellite. Among other things, we derive optimal strategies for constraining cosmological parameters using type Ia supernovae. The redshift range z~=0.2-2 has the most leverage for probing wX; supernovae and number counts appear to have the most potential to probe dark energy. Because the expansion rate depends upon both w(t) and ΩM, an independent measurement of the matter density is critical for obtaining the most information about dark energy from cosmological observations.

Title:
Reconstructing Dark Energy
Authors:
Sahni, Varun; Starobinsky, Alexei
Affiliation:
AA(Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007, , India; ), AB(Landau Institute for Theoretical Physics, Kosygina 2, Moscow 119334, , Russia; )
Publication:
International Journal of Modern Physics D, Volume 15, Issue 12, pp. 2105-2132 (2006). (IJMPD Homepage)
Publication Date:
00/2006
Origin:
WSPC
Keywords:
Dark energy, cosmic acceleration, cosmological reconstruction, cosmological constant, vacuum energy
DOI:
10.1142/S0218271806009704
Bibliographic Code:
2006IJMPD..15.2105S

Abstract

This review summarizes recent attempts to reconstruct the expansion history of the universe and to probe the nature of dark energy. Reconstruction methods can be broadly classified into parametric and non-parametric approaches. It is encouraging that, even with the limited observational data currently available, different approaches give consistent results for the reconstruction of the Hubble parameter H(z) and the effective equation of state w(z) of dark energy. Model independent reconstruction using current data allows for modest evolution of dark energy density with redshift. However, a cosmological constant (= dark energy with a constant energy density) remains an excellent fit to the data. Some pitfalls to be guarded against during cosmological reconstruction are summarized and future directions for the model independent reconstruction of dark energy are explored.

Title:
Dark Energy and the Accelerating Universe
Authors:
Frieman, Joshua A.; Turner, Michael S.; Huterer, Dragan
Publication:
Annual Review of Astronomy & Astrophysics, vol. 46, Issue 1, pp.385-432 (Annual Reviews Homepage)
Publication Date:
09/2008
Origin:
WEB
DOI:
10.1146/annurev.astro.46.060407.145243
Bibliographic Code:
2008ARA&A..46..385F

Abstract

Ten years ago, the discovery that the expansion of the universe is accelerating put in place the last major building block of the present cosmological model, in which the universe is composed of 4% baryons, 20% dark matter, and 76% dark energy. At the same time, it posed one of the most profound mysteries in all of science, with deep connections to both astrophysics and particle physics. Cosmic acceleration could arise from the repulsive gravity of dark energy—for example, the quantum energy of the vacuum—or it may signal that general relativity (GR) breaks down on cosmological scales and must be replaced. We review the present observational evidence for cosmic acceleration and what it has revealed about dark energy, discuss the various theoretical ideas that have been proposed to explain acceleration, and describe the key observational probes that will shed light on this enigma in the coming years.

Title:
The dynamics of quintessence, the quintessence of dynamics
Authors:
Linder, Eric V.
Affiliation:
AA(Berkeley Lab, University of California)
Publication:
General Relativity and Gravitation, Volume 40, Issue 2-3, pp. 329-356 (GReGr Homepage)
Publication Date:
02/2008
Origin:
SPRINGER
DOI:
10.1007/s10714-007-0550-z
Bibliographic Code:
2008GReGr..40..329L

Abstract

Quintessence theories for cosmic acceleration imbue dark energy with a non-trivial dynamics that offers hope in distinguishing the physical origin of this component. We review quintessence models with an emphasis on the dynamics and discuss classifications of the different physical behaviors. The pros and cons of various parameterizations are examined as well as the extension from scalar fields to other modifications of the Friedmann expansion equation. New results on the ability of cosmological data to distinguish among and between thawing and freezing fields are presented.

Title:
The acceleration of the universe and the physics behind it
Authors:
Uzan, Jean-Philippe
Publication:
eprint arXiv:astro-ph/0605313
Publication Date:
05/2006
Origin:
ARXIV
Keywords:
Astrophysics, General Relativity and Quantum Cosmology, High Energy Physics - Phenomenology
Comment:
18 pages, 18 figures; Gen.Rel.Grav.39:307-342,2007; doi:10.1007/s10714-006-0385-z
Bibliographic Code:
2006astro.ph..5313U

Abstract

Using a general classification of dark enegy models in four classes, we discuss the complementarity of cosmological observations to tackle down the physics beyond the acceleration of our universe. We discuss the tests distinguishing the four classes and then focus on the dynamics of the perturbations in the Newtonian regime. We also exhibit explicitely models that have identical predictions for a subset of observations.