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:
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.
Fr.: métrique de Schwarzschild
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.
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.
Of or relating to → spectrophotometry.
Of or relating to → spectropolarimetry.
1) Of or pertaining to → stoichiometry.
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.
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.
Characterized by or exhibiting → symmetry.
Adj. of → symmetry.
Fr.: trigonométrique, circulaire
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.
didgašt-e sebarsanji, ~ sebarsanjik
Fr.: parallaxe trigonométrique