anisotropic homogeneous cosmological model
model-e keyhânšenâxti-ye hamgen o nâ-izogard
Fr.: modèle cosmiologique homogène mais anisotrope
Bianchi cosmological model
model-e keyhânšenâxti-ye Bianchi
Fr.: modèle cosmologique de Bianchi
A cosmological model based on the theory of → general relativity, which is homogeneous but → anisotropic. There are actually ten dinstinct Bianchi types, classified according to the particular kinds of symmetry they posses.
Pertaining or relating to → cosmology.
pâyâ-ye keyhânšenâsik, ~ keyhânšenâxti
Fr.: constante cosmologique
A term introduced by Einstein into his gravitational → field equations in order to allow a solution corresponding to a → static Universe. The cosmological constant is physically interpreted as due to the → vacuum energy of quantized fields. See also → dark energy.
cosmological constant problem
parâse-ye pâyâ-ye keyhânšenâxti
Fr.: problème de la constante cosmologique
The impressive discrepancy of about 120 orders of magnitude between the theoretical value of the → cosmological constant and its observed value. → Quantum field theory interprets the cosmological constant as the density of the → vacuum energy. This density can be derived from the maximum energy at which the theory is valid, i.e. the → Planck energy scale (1018 GeV). The theoretical vacuum → energy density is (1018 GeV)4 = (1027 eV)4 = 10112 erg cm-3. On the other hand, the observed vacuum energy density is estimated to be about (10-3 eV)4 = 10-8 erg cm-3. There is, therefore, a discrepancy of about 120 orders of magnitude.
durâ-ye keyhânšenâsik, ~ keyhânšenâxti
Fr.: distance cosmologique
The distance to a remote galaxy based on its redshift assuming that the redshift is caused by the → Doppler effect and reflects the general expansion of the Universe.
model-e keyhânšenâsik, ~ keyhânšenâxti
Fr.: modèle cosmologique
A mathematical description of the Universe, based on observation, which tries to explain its current aspect, and to describe its evolution during time.
parvaz-e keyhânšenâsik, ~ keyhânšenâxti
Fr.: principe cosmologique
The → hypothesis that on → large scales the → Universe is → isotropic and → homogeneous, that is, it appears the same at all places and, from any one place, looks the same in all directions. See also → perfect cosmological principle.
sorxkib-e keyhânšenâsik, ~ keyhânšenâxti
Fr.: décalage vers le rouge cosmologique, redshift ~
The → redshift of a remote object (galaxy, quasar, supenova) due to the expansion of the Universe.
current cosmological epoch
zime-ye keyhânšenâxti-ye konuni
Fr.: époque cosmologique actuelle
The Universe at the → redshift z = 0.
Milne cosmological model
model-e keyhânšenâxti-ye Milne (#)
Fr.: modèle cosmologique de Milne
Same as → Milne Universe.
perfect cosmological principle
parvaz-e keyhânšenâsik-e farsâxt
Fr.: principe cosmologique parfait
The → assumption, adopted by the → steady-state theory, that all observers, everywhere at all times, would view the same large-scale distribution of matter in the → Universe in all regions and in every direction. In contrast to the → cosmological principle, the perfect cosmological principle adds the assumption that the Universe does not change with time on the large scale.