Vacuum Energy: If Not Now, Then When?

Abstract

We review the cosmological evidence for a low matter density universe and a cosmological constant or dynamical vacuum energy and address the cosmolog$ coincidence problem: why is the matter density about one-half the vacuum energy {\em now}. This is reasonble, following the anthropic argument of Efstathiou and of Martel, Schapiro & Weinberg.

4 pages (latex)

References in corpus (4)

• Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
• Supernova Limits on the Cosmic Equation of State
• Likely Values of the Cosmological Constant
• Baryonic Mass Fraction in Rich Clusters and the Total Mass Density in the Cosmos

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• Tracking Dark Energy with the ISW effect: short and long-term predictions
• Dark Energy in Practice
• Toward a Possible Solution to the Cosmic Coincidence Problem
• Forecasting Cosmic Doomsday from CMB/LSS Cross-Correlations
• Field theory models for variable cosmological constant
• Anthropic prediction in a large toy landscape
• Taming the Runaway Problem of Inflationary Landscapes
• A quantum cosmology approach to cosmic coincidence and inflation
• Anthropic prediction for a large multi-jump landscape
• A stringy perspective on the coincidence problem
• The vacuum energy crisis
• Cosmological Constraints on the Undulant Universe