# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

Homepage

Number of Results: 13116 Search : far
 EHB star   ستاره‌ی ِ EHB   setâre-ye EHBFr.: étoile EBH   Same as → extreme horizontal branch star. eigenfunction   ویژکریا   viž-karyâFr.: 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." eigenstate   ویژ حالت   viž-hâlatFr.: 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. eigenvalue   ویژ ارزه   viž-arzéFr.: 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. eigenvector   ویژبردار   viž-bordârFr.: 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. eight   هشت   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   اینشتین   einstein (#)Fr.: einstein   A unit of radiation energy sometimes used in the investigation of photochemical processes. The unit is defined as NAhν, where NA is → Avogadro's number and hν 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 EinsteinFr.: 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 EinsteinFr.: 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 EinsteinFr.: 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 EinsteinFr.: 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 EinsteinFr.: 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) ai.bi. In the Einstein notation this is simply written as a.b = ai.bi. This notation makes operations much easier. Same as Einstein summation convention.→ Einstein; → notation. Einstein radius   شعاع ِ اینشتین   šo'â'-e EinsteinFr.: rayon d'Einstein   In gravitational lens phenomenon, the critical distance from the → lensing object for which the light ray from the source is deflected to the observer, provided that the source, the lens, and the observer are exactly aligned. Consider a massive object (the lens) situated exactly on the line of sight from Earth to a background source. The light rays from the source passing the lens at different distances are bent toward the lens. Since the bending angle for a light ray increases with decreasing distance from the lens, there is a critical distance such that the ray will be deflected just enough to hit the Earth. This distance is called the Einstein radius. By rotational symmetry about the Earth-source axis, an observer on Earth with perfect resolution would see the source lensed into an annulus, called Einstein ring, centered on its position. The size of an Einstein ring is given by the Einstein radius: θE = (4GM/c2)0.5 (dLS/(dL.dS)0.5, where G is the → gravitational constant, M is the mass of the lens, c is the → speed of light, dL is the angular diameter distance to the lens, dS is the angular diameter distance to the source, and dLS is the angular diameter distance between the lens and the source. The equation can be simplified to: θE = (0''.9) (M/1011Msun)0.5 (D/Gpc)-0.5. Hence, for a dense cluster with mass M ~ 10 × 1015 Msun at a distance of 1 Gigaparsec (1 Gpc) this radius is about 100 arcsec. For a gravitational → microlensing event (with masses of order 1 Msun) at galactic distances (say D ~ 3 kpc), the typical Einstein radius would be of order milli-arcseconds.→ Einstein; → radius. Einstein ring   حلقه‌ی ِ اینشتین   halqe-ye EinsteinFr.: anneau d'Einstein   The apparent shape of a background source unsergoing the effect of → gravitational lensing as seen from Earth, provided that the source, the intervening lens, and the observer are in perfect alignement through → Einstein radius.→ Einstein; → ring. Einstein solid   مدل ِ اینشتین   model-e EinsteinFr.: modèle d'Einstein   Same as → Einstein model.→ Einstein; → solid. Einstein static Universe   گیتی ِ ایستای ِ اینشتین   giti-ye istâ-ye EinsteinFr.: 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 time-scale   مرپل ِ زمانی ِ اینشتین   marpel-e zamâni-ye EinsteinFr.: échelle de temps d'Einstein   The time during which a → microlensing event occurs. It is given by the equation tE = RE/v, where RE is the → Einstein radius, v is the magnitude of the relative transverse velocity between source and lens projected onto the lens plane. The characteristic time-scale of → microlensing events is about 25 days.→ Einstein; → time-scale. Einstein's elevator   بالابر ِ اینشتین   bâlâbar-e EinsteinFr.: 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.