An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 12 Search : cosmological
anisotropic homogeneous cosmological model
  مدل ِ کیهانشناختی ِ همگن و نا-ایزوگرد   
model-e keyhânšenâxti-ye hamgen o nâ-izogard

Fr.: modèle cosmiologique homogène mais anisotrope   

A solution to Einstein's theory of → general relativity that is spatially homogeneous but allows for rotation and/or shear. See also → Bianchi cosmological model.

anisotropic; → homogeneous; → cosmological; → model.

Bianchi cosmological model
  مدل ِ کیهانشناختی ِ بیانکی   
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.

Luigi Bianchi (1856-1928), Italian mathematician; → cosmological; → model.

cosmological
  کیهان‌شناختی، کیهان‌شناسیک   
keyhânšenâxti, keyhânšenâsik

Fr.: cosmologique   

Pertaining or relating to → cosmology.

cosmology; → -al.

cosmological constant
  پایای ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
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.

cosmological constant problem
  پراسه‌ی ِ پایای ِ کیهانشناختی   
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.

cosmological; → constant; → problem.

cosmological distance
  دورای ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
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.

cosmological; → distance .

cosmological model
  مدل ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
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.

cosmological; → model.

cosmological principle
  پروز ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
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.

Introduced by E.A. Milne in 1933; → cosmological; → principle.

cosmological redshift
  سرخ کیب ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
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.

cosmological; → redshift.

current cosmological epoch
  زیمه‌ی ِ کیهانشناختی ِ کنونی   
zime-ye keyhânšenâxti-ye konuni

Fr.: époque cosmologique actuelle   

The Universe at the → redshift z = 0.

current; → present; → cosmological; → epoch.

Milne cosmological model
  مدل ِ کیهان‌شناختی ِ میلن   
model-e keyhânšenâxti-ye Milne (#)

Fr.: modèle cosmologique de Milne   

Same as → Milne Universe.

Milne Universe; → cosmological; → model.

perfect cosmological principle
  پروز ِ کیهان‌شناسیک ِ فرساخت   
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.

perfect; → cosmological; → principle.