# cosmological constant

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## cosmological constant

(koz-mŏ-loj -ă-kăl) A constant term that can be added to Einstein's field equations of general relativity theory. The cosmological constant was originally put forward by Albert Einstein in 1917 to ensure that the application of general relativity theory to the Universe results in a static Universe rather than an expanding or contracting Universe. The discovery that the Universe is expanding removed the necessity for introducing the cosmological constant but cosmological models with a nonzero cosmological constant have been considered by theoreticians.

For many years it was thought that the value of the cosmological constant is exactly zero but, starting in the late 1990s, evidence began to accumulate that the cosmological constant has a small but nonzero value. This has the consequence that the expansion of the Universe is accelerating. There have been many attempts to show why the value of the cosmological constant is either zero or very small but there is no consensus as to why this should be the case.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Cosmological Constant

the constant A introduced by A. Einstein in 1917 into his equations of gravitation (1916) so that these equations would have solutions describing a static universe and would satisfy the requirement of the relativity of inertia. The physical meaning of the introduction of the constant consists in the assumed existence of special cosmic forces (of repulsion at ∧ > 0 and of attraction at ∧ < 0) that increase with distance. Since the requirement of a static universe became redundant with the discovery that galaxies are receding from one another, Einstein abandoned the cosmological constant in 1931. From this time on, it was assumed that ∧ ≡ 0. Another possibility is being considered at present (the 1970’s), namely, that the cosmological constant is extremely small (∽10−55 cm−2).

### REFERENCE

Zel’dovich, la. B., and I. D. Novikov. Reliativistskaia astrofizika. Moscow, 1967.

G. I. NAAN

## cosmological constant

[¦käz·mə¦läj·ə·kəl ′kän·stənt]
(relativity)
The multiplicative constant for a term proportional to the metric in Einstein's equation relating the curvature of space to the energy-momentum tensor.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Zhitnitsky, "Cosmological constant from the ghost: a toy model," Physical Review D: Particles, Fields, Gravitation and Cosmology, vol.
Poplawski, "Cosmological constant from quarks and torsion," Annalen der Physik, vol.
Vitiello, "Dark energy, cosmological constant and neutrino mixing," International Journal of Modern Physics A, vol.
Such universe models can theoretically exist but must involve very long coasting phases, which are difficult to compute accurately even in double-precision arithmetic since the delicate relationship between the attraction of gravity and the repulsion of the cosmological constant is an unstable one.
Running the program with an empty universe ([[Omega].sub.0] = 0) and no cosmological constant term ([[Omega].sub.[Lambda]] = 0) gives a simple straight-line graph.
Hollowood, "General properties of the self-tuning domain wall approach to the cosmological constant problem," Nuclear Physics B, vol.
Toporensky, "Induced cosmological constant and other features of asymmetric brane embedding," Journal of Cosmology and Astroparticle Physics, vol.

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