cosmological constant

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Cosmological models with different deceleration parametersclick for a larger image
Cosmological models with different deceleration parameters

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.

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).


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


cosmological constant

[¦käz·mə¦läj·ə·kəl ′kän·stənt]
The multiplicative constant for a term proportional to the metric in Einstein's equation relating the curvature of space to the energy-momentum tensor.
References in periodicals archive ?
In the de Sitter cosmology, the cosmological constant [LAMBDA] corresponding to a positive vacuum energy density sets the expansion rate H = -[square root of 1/3 [LAMBDA]] for a flat Universe, which is the photon energy decay rate of light traveling in vacuum.
Moreover the cosmological constant [lambda] satisfies the relation r + 6[[alpha].
Equation (82) can be considered as the gauge of the cosmological constant, with which it is possible to use Equation (81) to find the metric.
In questions to Dr Trotta, Sheridan Williams asked whether the cosmological constant is generally accepted as the explanation of dark energy.
Weinberg, "Anthropic Bound on the Cosmological Constant," Physical Review Letters 59 (1987): 2607-10; V.
Again an Einstein equation with cosmological constant is given by
The cosmological constant contribution to the curvature of space-time is represented by the term [LAMBDA].
Berman (Instituto Albert Einstein, Brazil) writes for undergraduates who need an introduction to general relativity theory and the cosmological constant (lambda) problem.
However, the observed cosmological constant (lambda) is perhaps as much as 1,000 times lower than its estimated value (Weinberg, 1989; Carroll and Press, 1992).
Einstein fudged his equations with a mythical cosmological constant to avoid the implications of his own work--a suggestion that the universe wasn't static and unchanging--which contradicted his own beliefs as well as the conventional wisdom of his time.
The cosmological constant is usually associated with the energy of the vacuum.