An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



Number of Results: 11 Search : scalar
electric scalar potential
  توند ِ مرپلی ِ برقی   
tavand-e marpeli-ye barqi

Fr.: potentiel électrique scalaire   

A potential φ defined so that the → electric field  E is expressed by a combination of its → gradient and the variation of the → magnetic vector potential over time: E = -∇φ -∂A/∂t.

electric; → scalar; → potential.

Ricci scalar
  مرپلی ِ ریتچی   
marpeli-ye Ricci

Fr.: scalaire de Ricci   

The simplest curvature invariant for a → Riemannian manifold. It is derived from the → Ricci tensor Rμν ≡  Rαμαν by contracting indices. Taking the trace of the Ricci tensor gives the Ricci scalar: R ≡ Rμνgμnu; = Rμν = Rαμαμ. Also called → scalar curvature.

Ricci tensor; → scalar.

  مرپلی، مرپل‌وار   
marpeli, marpelvâr

Fr.: scalaire   

Any quantity which is sufficiently defined only with its magnitude, when given in appropriate units. Compare → vector.
See also:
electric scalar potential, → scalar field, → scalar potential, → scalar processor, → scalar product, → scalar wave, → scalar-tensor theory, → tensor-vector-scalar (TeVeS) theory.

Of or pertaining to → scale.

scalar density
  چگالی ِ مرپلی   
cagâli-ye marpeli

Fr.: densité scalaire   

A → tensor density of → order 0.

scalar; → density.

scalar field
  میدان ِ مرپلی   
meydân-e marpeli

Fr.: champ scalaire   

A → field whose value at every point of space is independent of → direction and → position. Examples include → temperature distribution throughout space and → pressure distribution in a → fluid. Similarly, a → potential field, such as the Newtonian → gravitational field or the electric potential in → electrostatics are scalar fields. In quantum field theory, a scalar field is associated with → spin zero particles, such as → mesons or → bosons. Therefore, the → Higgs boson is associated with a scalar field. The → derivative of a scalar field results in a → vector field is called the → gradient. In contrast to a vector field, a scalar field is → invariant under the → rotation of the → coordinate system. The → inflation in the → early Universe is supposed to be driven by a scalar field, called the → inflaton field.

scalar; → field.

scalar perturbation
  پرتورش ِ مرپلی   
partureš-e marpeli

Fr.: perturbation scalaire   

The energy density fluctuations in the → photon-baryon plasma that bring about hotter and colder regions. This perturbation creates velocity distributions that are out of phase with the acoustic density mode. The fluid velocity from hot to cold regions causes blueshift of the photons, resulting in → quadrupole anisotropy.

scalar; → perturbation.

scalar processor
  آمایشگر ِ مرپلی   
âmâyeš:gar-e marpeli

Fr.: processeur scalaire   

Computers: A type of central processing unit in which only one operation on data is executed at a time. By contrast, in a vector processor, a single instruction operates simultaneously on multiple data items.

scalar; → processor.

scalar product
  فر‌آورد ِ مرپلی   
farâvard-e marpeli

Fr.: produit scalaire   

A multiplication of two vectors giving a scalar. The scaler product of V1 and V2 is defined by: V1.V2 = V1.V2 cos α, where V1 and V2 are the magnitudes of the vectors and α is the angle between them. Same as dot product. See also → vector product.

scalar; → product.

scalar wave
  موج ِ مرپلی   
mowj-e marpeli

Fr.: onde scalaire   

In theories of gravitation, a kind of → gravitational wave, transversal and/or longitudinal, characterized by → spin zero.

scalar; → wave.

scalar-tensor theory
  نگره‌ی ِ مرپلی-تانسوری   
negare-ye marpel-tânsori

Fr.: théorie scalaire-tensorielle   

An alternative to the standard → general relativity of gravity that contains not only the → tensor field (or → metric), but also a → scalar field. In this formalism, the → gravitational constant is considered to vary over time. As a consequence, the measured strength of the gravitational interaction is a function of time. Same as → Jordan-Brans-Dicke theory.

scalar; → tensor; → theory.

tensor-vector-scalar (TeVeS) theory


A theory put forward to provide a basis for a relativistic generalization of the → MOdified Newtonian Dynamics (MOND) paradigm. TeVeS is based on three dynamical fields: a tensor field, a vector field, and a scalar field. In contrast to general relativity, it has two metrics, an Einstein metric and a physical metric. TeVeS has attracted considerable attention, since it can explain many galactic and cosmological observations without the need for → dark matter. Proposed by J. D. Bekenstein, 2004, "Relativistic gravitation theory for the modified Newtonian dynamics paradigm", Phys. Rev. D, 70, 083509, arXiv:astro-ph/0403694.

tensor; → vector; → scalar; → theory.