Invited review for Annual Reviews of Astronomy and Astrophysics
arXiv:0803.0982v1

For a PDF version of the article, click here.

DARK ENERGY AND THE ACCELERATING UNIVERSE

Joshua A. Frieman

Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P. O. Box 500, Batavia, IL 60510;
Kavli Institute for Cosmological Physics, The University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637; email: frieman@fnal.gov

Michael S. Turner

Kavli Institute for Cosmological Physics, The University of Chicago, 5640 S. Ellis Ave., Chicago, IL 60637; email: mturner@uchicago.edu

Dragan Huterer

Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI, 48109; email: huterer@umich.edu


Key Words: cosmology, cosmological constant, supernovae, galaxy clusters, large-scale structure, weak gravitational lensing


Abstract. The discovery ten years ago 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 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.


Table of Contents

INTRODUCTION

BASIC COSMOLOGY
Friedmann-Robertson-Walker cosmology
Distances and the Hubble diagram
Growth of structure and Lambda CDM

FROM EINSTEIN TO ACCELERATED EXPANSION
Greatest blunder?
Steady state and after
Enter inflation
Discovery

CURRENT STATUS
Cosmic microwave background and large-scale structure
Recent supernova results
X-ray clusters
Age of the Universe
Cosmological parameters

UNDERSTANDING COSMIC ACCELERATION
Dark energy models
Modified gravity
Unmodified gravity
Theory summary

DESCRIBING DARK ENERGY
Parametrizations
Direct reconstruction
Principal components
Kinematic description

PROBES OF COSMIC ACCELERATION
Supernovae
Clusters
Baryon acoustic oscillations
Weak gravitational lensing
Other probes
Role of the CMB
Probing new gravitational physics
Summary and comparison

DARK ENERGY PROJECTS
Ground-based surveys
Space-based surveys

DARK ENERGY & COSMIC DESTINY

CONCLUDING REMARKS
Take-home facts
Open issues and challenges

APPENDIX
Figure(s) of merit
Fisher information matrix

REFERENCES

Next