An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 639
EHB star
  ستاره‌ی ِ EHB   
setâre-ye EHB

Fr.: étoile EBH   

Same as → extreme horizontal branch star.

extreme horizontal branch star.


Fr.: fonction propre   

1) Math.: An → eigenvector for a linear → operator on a → vector space whose vectors are → functions. Also known as proper function.
2) Quantum mechanics: A → wave function corresponding to an → eigenvalue. Eigenfunctions represent the stationary → quantum states of a system.

From Ger. Eigenfunktion, from eigen- "characteristic, particular, own" (from P.Gmc. *aigana- "possessed, owned," Du. eigen, O.E. agen "one's own") + → function.

Viž-karyâ, from viž, contraction of vižé "particular, charcteristic" + karyâ, → function. Vižé, from Mid.Pers. apēcak "pure, sacred," from *apa-vēcak "set apart," from prefix apa- + vēcak, from vēxtan (Mod.Pers. bixtan) "to detach, separate, sift, remove," Av. vaēk- "to select, sort out, sift," pr. vaēca-, Skt. vic-, vinakti "to sift, winnow, separate; to inquire."

  ویژ حالت   

Fr.: état propre   

Quantum mechanics: A dynamical state whose state vector (or wave function) is an → eigenvector of an → operator corresponding to a specified physical quantity.

eigenfunction; → state.

  ویژ ارزه   

Fr.: valeur propre   

1) Math.: The one of the → scalars λ such that T(v) = λv, where T is a linear → operator on a → vector space, and v is an → eigenvector.
2) Quantum mechanics: The specified values of → quantized energy for which the → Schrodinger equation is soluble, subject to the appropriate → boundary conditions.

eigenfunction; → value.


Fr.: vecteur propre   

Math.: A nonzero vector v whose direction is not changed by a given linear transformation T; that is, T(v) = λ v for some scalar λ.

eigenfunction; → vector.

hašt (#)

Fr.: huit   

A → cardinal number between → seven and → nine.

M.E. eighte, from O.E. eahta, æhta, related to O.Norse atta, Swed. åtta, Du. acht, O.H.G. Ahto, Ger. acht; Pars. hašt, as below, from PIE *okto(u) "eight."

Hašt, from Mid.Pers. hašt; Av. ašta; cognate with Skt. asta; Gk. okto; L. octo (from which It. otto, Sp. ocho, Fr. huit).

einstein (#)

Fr.: einstein   

A unit of radiation energy sometimes used in the investigation of photochemical processes. The unit is defined as NA, where NA is → Avogadro's number and is the energy of a → quantum of the radiation. One einstein (or Einstein unit) is the energy per → mole of photons carried by a beam of monochromatic light.

Named for Albert Einstein (1879-1955).

Einstein coefficient
  همگر ِ اینشتین   
hamgar-e Einstein

Fr.: coefficient d'Einstein   

A measure of the probability that a particular atomic transition leading to the formation of an atomic spectral line occurs. The coefficient of spontaneous emission is denoted by Aij, and the coefficient of stimulated emission by Bij, i representing the lower level and j is the upper level.

Named after Albert Einstein (1879-1955) who introduced the coefficients in 1916; → coefficient.

Einstein cross
  چلیپای ِ اینشتین   
calipâ-ye Einstein

Fr.: croix d'Einstein   

An image of a distant quasar (redshift 1.7) formed by a foreground spiral galaxy (redshift 0.039) through gravitational lensing. The image of the quasar is split into four point sources forming a cross at the center of the galaxy.

Einstein; → cross.

Einstein equivalence principle
  پروز ِ هموگ-ارزی ِ اینشتین   
parvaz-e hamug-arzi-ye Einstein

Fr.: principe d'équivalence d'Einstein   

The → equivalence principle as stated by Einstein, on which is based the theory of → general relativity. It comprises the three following items:
1) The → weak equivalence principle is valid.
2) The outcome of any local non-gravitational experiment is independent of the velocity of the freely-falling → reference frame in which it is performed. Also known as → local Lorentz invariance.
3) The outcome of any local non-gravitational experiment is independent of where and when in the Universe it is performed. Also called → local position invariance.

Einstein; → equivalence; → principle.

Einstein model
  مدل ِ اینشتین   
model-e Einstein

Fr.: modèle d'Einstein   

A model for the → specific heat of solids in which the specific heat is due to the vibrations of the atoms of the solids. The vibration energy is → quantized and the atoms have a single frequency, ν. Put forward in 1907 by Einstein, this model was the first application of → quantum theory to the solid state physics. The expression for the specific heat is given by: CV = 3Rx2ex/(ex -1)2, where R is the → gas constant, x = TE/T, TE = hν/k, h is → Planck's constant, and k is → Boltzmann's constant. TE is called the → Einstein temperature. This model could explain the temperature behavior of specific heat but not very satisfactorily at low temperatures. It has therefore been superseded by the → Debye model. See also → Dulong-Petit law.

Albert Einstein in 1907; → model.

Einstein notation
  نمادگان ِ اینشتین   
namâdgân-e Einstein

Fr.: convention Einstein   

A notation convention in → tensor analysis whereby whenever there is an expression with a repeated → index, the summation is done over that index from 1 to 3 (or from 1 to n, where n is the space dimension). For example, the dot product of vectors a and b is usually written as: a.b = Σ (i = 1 to 3) In the Einstein notation this is simply written as a.b = This notation makes operations much easier. Same as Einstein summation convention.

Einstein; → notation.

Einstein solid
  مدل ِ اینشتین   
model-e Einstein

Fr.: modèle d'Einstein   

Same as → Einstein model.

Einstein; → solid.

Einstein static Universe
  گیتی ِ ایستای ِ اینشتین   
giti-ye istâ-ye Einstein

Fr.: Univers stationnaire d'Einstein   

A cosmological model in which a static (neither expanding nor collapsing) Universe is maintained by introducing a cosmological repulsion force (in the form of the cosmological constant) to counterbalance the gravitational force.

Einstein; → static; arr; universe.

Einstein temperature
  دمای ِ اینشتین   
damâ-ye Einstein (#)

Fr.: température d'Einstein   

A characteristic parameter occurring in the → Einstein model of → specific heats.

Einstein; → temperature.

Einstein tensor
  تانسور ِ اینشتین   
tânsor-e Einstein (#)

Fr.: tenseur d'Einstein   

A mathematical entity describing the → curvature of → space-time in → Einstein's field equations, according to the theory of → general relativity. It is expressed by Gμν = Rμν - (1/2) gμνR, where Rμν is the Ricci tensor, gμν is the → metric tensor, and R the scalar curvature. This tensor is both symmetric and divergence free.

Named after Albert Einstein (1879-1955); → tensor.

Einstein's elevator
  بالابر ِ اینشتین   
bâlâbar-e Einstein

Fr.: ascenseur d'Einstein   

A → thought experiment, involving an elevator, first conceived by Einstein to show the → principle of equivalence. According to this experiment, it is impossible for an observer situated inside a closed elevator to decide if the elevator is being pulled upward by a constant force or is subject to a gravitational field acting downward on a stationary elevator. Einstein used this experiment and the principle of equivalence to deduce the bending of light by the force of gravity.

einstein; elevator, from L. elevator, agent noun from p.p. stem of elevare "to lift up, raise," from → ex- "out" + levare "lighten, raise," from levis "light" in weight, → lever.

Bâlâbar, → lift.

Einstein's field equations
  هموگش‌های ِ میدان ِ اینشتین   
hamugešhâ-ye meydân-e Einstein

Fr.: équations de champ d'Einstein   

A system of ten non-linear → partial differential equations in the theory of → general relativity which relate the curvature of → space-time with the distribution of matter-energy. They have the form: Gμν = -κ Tμν, where Gμν is the → Einstein tensor (a function of the → metric tensor), κ is a coupling constant called the → Einstein gravitational constant, and Tμν is the → energy-momentum tensor. The field equations mean that the curvature of space-time is due to the distribution of mass-energy in space. A more general form of the field equations proposed by Einstein is: Gμν + Λgμν = - κTμν, where Λ is the → cosmological constant.

Named after Albert Einstein (1879-1955); → field; → equation.

Einstein's gravitational constant
  پایای ِ گرانشی ِ اینشتین   
pâyâ-ye gerâneši-ye Einstein (#)

Fr.: constante gravitationnelle d'Einstein   

The coupling constant appearing in → Einstein's field equations, expressed by: κ = 8πG/c4, where G is the Newtonian → gravitational constant and c the → speed of light.

einstein; → gravitational; → constant.

Einstein's theory of specific heat
  نگره‌ی ِ گرمای ِ آبیزه‌ی ِ اینشتین   
negare-ye garmâ-ye âbize-ye Einstein

Fr.: théorie de la chaleur spécifique d'Einstein   

Same as → Einstein model.

Einstein; → theory; → specific heat.

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