Everpresent Lambda

• Main Authors: Ahmed, Maqbool, Dodelson, Scott, Greene, Patrick B, Sorkin, Rafael
• Format: Journal Article
• Language: English
• Published: 13.09.2002
• Subjects: Physics - Astrophysics of Galaxies; Physics - Cosmology and Nongalactic Astrophysics; Physics - Earth and Planetary Astrophysics; Physics - General Relativity and Quantum Cosmology; Physics - High Energy Astrophysical Phenomena; Physics - High Energy Physics - Theory; Physics - Instrumentation and Methods for Astrophysics; Physics - Solar and Stellar Astrophysics
• DOI: 10.48550/arxiv.astro-ph/0209274

Phys.Rev.D69:103523,2004 A variety of observations indicate that the universe is dominated by dark energy with negative pressure, one possibility for which is a cosmological constant. If the dark energy is a cosmological constant, a fundamental question is: Why has it become relevant at so late an epoch, making today the only time in the history of the universe at which the cosmological constant is of order the ambient density. We explore an answer to this question drawing on ideas from unimodular gravity, which predicts fluctuations in the cosmological constant, and causal set theory, which predicts the magnitude of these fluctuations. The resulting ansatz yields a fluctuating cosmological ``constant'' which is always of order the ambient density.