Abstract
Recent observations of Type 1a supernovae indicating an accelerating universe have once more drawn attention to the possible existence, at the present epoch, of a small positive Λ-term (cosmological constant). In this paper we review both observational and theoretical aspects of a small cosmological Λ-term. We discuss the current observational situation focusing on cosmological tests of Λ including the age of the universe, high redshift supernovae, gravitational lensing, galaxy clustering and the cosmic microwave background. We also review the theoretical debate surrounding Λ: the generation of Λ in models with spontaneous symmetry breaking and through quantum vacuum polarization effects — mechanisms which are known to give rise to a large value of Λ hence leading to the "cosmological constant problem." More recent attempts to generate a small cosmological constant at the present epoch using either field theoretic techniques, or by modelling a dynamical Λ-term by scalar fields are also extensively discussed. Anthropic arguments favouring a small Λ-term are briefly reviewed. A comprehensive bibliography of recent work on Λ is provided.
Keywords
PhysicsCosmological constantLambda-CDM modelCosmic microwave backgroundNon-standard cosmologyMetric expansion of spaceAstrophysicsTheoretical physicsCosmologyPhysical cosmologyGalaxyDark energyQuantum mechanics
Affiliated Institutions
Related Publications
Measurement of the Cosmic Microwave Background Polarization Lensing Power Spectrum with the POLARBEAR Experiment
Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale ...
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: baryon acoustic oscillations in the Data Release 9 spectroscopic galaxy sample
We present measurements of galaxy clustering from the Baryon Oscillation\nSpectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey III\n(SDSS-III). These use t...
First‐Year <i>Wilkinson Microwave Anisotropy Probe</i> ( <i>WMAP</i> ) Observations: Determination of Cosmological Parameters
WMAP precision data enables accurate testing of cosmological models. We find that the emerging standard model of cosmology, a flat Λ−dominated universe seeded by a nearly scalei...
CFHTLenS tomographic weak lensing: quantifying accurate redshift distributions
The Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS) comprises deep multicolour (u^*g′r′i′z′) photometry spanning 154 deg^2, with accurate photometric redshifts and shap...
Planck 2018 results. VI. Cosmological parameters
We present cosmological parameter results from the final full-mission Planck\nmeasurements of the CMB anisotropies. We find good consistency with the\nstandard spatially-flat 6-...
Publication Info
- Year
- 2000
- Type
- article
- Volume
- 09
- Issue
- 04
- Pages
- 373-443
- Citations
- 2539
- Access
- Closed
External Links
Social Impact
Altmetric
PlumX Metrics
Social media, news, blog, policy document mentions
Citation Metrics
2539
OpenAlex
Cite This
Varun Sahni,
Alexei A. Starobinsky
(2000).
THE CASE FOR A POSITIVE COSMOLOGICAL Λ-TERM.
International Journal of Modern Physics D
, 09
(04)
, 373-443.
https://doi.org/10.1142/s0218271800000542
Identifiers
- DOI
- 10.1142/s0218271800000542