An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 53 Search : metric
Robertson-Walker metric
  متریک ِ روبرتسون-واکر   
metrik-e Robertson-Walker (#)

Fr.: métrique de Robertson-Walker   

The mathematical description of the interval (→ space-time separation) between → events ("points" in space-time) in a → homogeneous and → isotropic → Universe. It results from an exact solution of → Einstein's field equations of → general relativity. Under the assumptions, the Robertson-Walker interval is expressed by:
ds2 = c2dt2 - R2(t) [dr2/(1 - kr2) + r22 + r2sin2θ dθ2)].
Same as Friedmann-Lemaître-Robertson-Walker metric. Compare → Minkowski metric.

Named after Howard Percy Robertson (1903-1961), American mathematician and physicist, and Arthur Geoffrey Walker (1909-2001), British mathematician and physicist, for their contributions to physics and physical cosmology; → metric.

Schwarzschild metric
  متریک ِ شو‌آرتسشیلد   
metrik-e Schwarzschild

Fr.: métrique de Schwarzschild   

In → general relativity, the → metric that describes the → space-time outside a static mass with spherically symmetric distribution.

Schwarzschild black hole; → metric.

skew-symmetric tensor
  تانسور ِ پاد-همامون   
tânsor-e pâdhamâmun

Fr.: tenseur antisymétrique   

A tensor that is the negative of its → transpose. For example, a second-order covariant tensor Ajk if its components satisfy the equality: Ajk = - Akj. Also called antisymmetric tensor.

skew; → symmetric; → tensor.

Tânsor, → tensor; pâd-, → anti-; hamâmun, → symmetric.

Spectro-Polarimetric High-contrast Exoplanet (SPHERE)
     

Fr.: Spectro-Polarimetric High-contrast Exoplanet (SPHERE)   

The → extreme adaptive optics system and → coronagraphic facility at the → European Southern Observatory (ESO) → Very Large Telescope (VLT) (UT3) available from May 2014. Its primary science goal is imaging, low-resolution spectroscopic, and polarimetric characterization of → exoplanetary system at → visible and → near-infrared wavelengths (0.5-2.32 μm). SPHERE is capable of obtaining → diffraction-limited images at 0''.02 to 0''.08 resolution depending on the wavelength. Its → spectral resolution is 30 to 350, depending on the mode.

spectro-; → polarimetric; → high; → contrast; → exoplanet.

spectrophotometric
  بیناب-شیدسنجیک   
binâb-šidsanjik

Fr.: spectrophotométrie   

Of or relating to → spectrophotometry.

spectrum; → photometry.

spectropolarimetric
  بیناب-قطبش‌سنجی، بیناب-قطبش‌سنجیک   
binâb-qotbešsanji, binâb-qotbešsanjik

Fr.: spectropoolarimétrique   

Of or relating to → spectropolarimetry.

spectropolarimetry; → -ic.

stoichiometric
  استویخیوسنجیک   
stoyxiyosanjik

Fr.: stoechiométrique   

1) Of or pertaining to → stoichiometry.
2) Pertaining to or involving substances that are in the exact proportions required for a given reaction.

stoichiometry; → -ic.

symmetric relation
  بازانش ِ همامون   
bâzâneš-e hamâmun

Fr.: relation symétrique   

A relation between two quantities such that the first is to the second as the second is to the first. In symbols: a R b = b R a. For example, multiplication is an operation with a symmetric relation between the factors: 5 x 3 = 3 x 5.

symmetric; → relation.

symmetric tensor
  تانسور ِ همامون   
tânsor-e hamâmun

Fr.: tenseur symétrique   

A tensor that is → invariant under any → permutation of its indices (→ index). In other words, a tensor that equals its → transpose. For example, a second-order → covariant tensor Ajk if its components satisfy the equality: Ajk = Akj.

symmetric; → tensor.

symmetric, symmetrical
  همامون   
hamâmun

Fr.: symétrique   

Characterized by or exhibiting → symmetry.

Adj. of → symmetry.

trigonometric
  سه‌برسنجیک   
sebarsanjik

Fr.: trigonométrique, circulaire   

Relating to or used in → trigonometry. → trigonometric function.

trigonometry; → -ic.

trigonometric function
  کریای ِ سه‌برسنجیک   
karyâ-ye sebarsanjik

Fr.: fonction circulaire, ~ trigonomtérique   

A function of an angle, one of six functions (sine, cosine, tangent, cotangent, secant, and cosecant) that represent ratios of sides of right triangles. Also called circular function.

trigonometric; → function.

trigonometric parallax
  دیدگشت ِ سه‌برسنجی، ~ سه‌برسنجیک   
didgašt-e sebarsanji, ~ sebarsanjik

Fr.: parallaxe trigonométrique   

The → parallax of a nearby star (less than 300 → light-years) against the background of more distant stars resulting from the motion of the Earth in its orbit around the Sun.

trigonometric; → parallax.

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