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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 153 Search : ten
 tensor contraction   ترنگش ِ تانسور   terengeš-e tânsorFr.: contraction de tenseur   An operation of tensor algebra that is obtained by setting unlike indices equal and summing according to a summation convention.→ contraction; → tensor. tensor density   چگالی ِ تانسور   cagâli-ye tânsorFr.: densité de tenseur   A generalization of the tensor concept that like a tensor transforms, except for the appearance of an extra factor, which is the → Jacobian matrix of the transformation of the coordinates, raised to some power, in transformation law. The exponent, which is a positive or negative integer, is called the weight of the tensor density. → weight of a tensor density. Ordinary tensors are tensor densities of weight 0. Tensor density is also called → relative tensor.→ tensor; → density. tensor field   میدان ِ تانسوری   meydân-e tânsoriFr.: champ tensoriel   A field of space and time each point of which has multiple directionality, and is describable by a tensor function.→ tensor; → field. tensor perturbation   پرتورش ِ تانسوری   partureš-e tânsoriFr.: perturbation tensorielle   The perturbation in the → primordial Universe plasma caused by → gravitational waves. These waves stretch and squeeze space in orthogonal directions and bring about → quadrupole anisotropy in incoming radiation temperature.→ tensor; → perturbation. tensor rank   رتبه‌ی ِ تانسور   rotbe-ye tânsorFr.: rang de tenseur   The total number of → contravariant and → covariant indices (→ index) of a → tensor.→ tensor; → rank. tensor-vector-scalar (TeVeS) theory      Fr.:   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. thermodynamic potential   توند ِ گرماتوانیک   tavand-e garmâtavânikFr.: potentiel thermodynaique   A measure of the energy level of a → thermodynamic system. It represents the amount of → work obtainable when the system undergoes a → change. The main types of thermodynamic potential are: → internal energy, → enthalpy, the → Helmholtz free energy, and the → Gibbs free energy. threaten   هرشیدن   haršidanFr.: menacer   1) To utter a threat against; menace. 2) To be a menace or source of danger to (Dictionary.com).From M.E. thretnen, from O.E. thrêatnian, → threatInfinitive from harš, → threat. tungsten   تنگستن   tangestan (#)Fr.: tungstène   A very hard, silver-white to steel-gray metal with a body-centered cubic crystalline structure; symbol W. Atomic number 74; atomic weight 183.85; melting point about 3,410°C; boiling point 5,660°C; specific gravity 19.3 at 20°C. The chemical element was discovered by the Swedish chemist Carl-Wilhelm Scheele in 1781. Tungsten metal was first isolated by the Spanish chemists Don Fausto d'Elhuyar and his brother Don Juan Jose d'Elhuyar in 1783.The name derives from the Swedish ng sten "heavy stone". The chemical symbol, W, is derived from the Ger. wolfram, which was found with tin and interfered with the smelting of tin. weight of a tensor density   وزن ِ چگالی ِ تانسور   vazn-e cagâli-ye tânsorFr.: poids d'une densité de tenseur   A constant the value of which is characteristic for any given → tensor density.→ weight; → tensor; → density. X-ray persistent   پرتو ِ X پریستنده   partow-e X paristandéFr.: rayons X persistants   An → X-ray source that does not display emission → outbursts, in contrast to → X-ray transients.→ X-ray; → persistent. Yagi antenna   آنتن ِ یاگی   ânten-e Yâgi (#)Fr.: antenne de Yagi   A very familiar antenna array, which is the commonest kind of terrestrial TV aerial to be found on the rooftops of houses. It consists of a single "feed" or "driven element," usually a dipole antenna. The rest of the elements help transmit the energy in a particular direction. These antennas typically operate in the HF to UHF bands (about 3 MHz to 3 GHz), although their bandwidth is typically small. In astronomy Yagi antennas are used as elements in some → radio interferometers. Same as Yagi-Uda antenna.Named after the Japanese electrical engineer Hidetsuga Yagi (1886-1976); → antenna. Yukawa potential   توند ِ یوکاوا   tavand-e YukawaFr.: potentiel de Yukawa   The potential function that is associated with the strong, short-ranged force resulting from the exchange of massive particles between two → nucleons in the same atomic nucleus. The potential has the form of V(r) = C. (1/r) exp (-K.r), where r is the distance between the nucleons and C and K are constants, giving measures of the strength and range of the force respectively.In honor of the Japanese physicist Hideki Yukawa (1907-1981), winner of the 1949 Nobel Prize in Physics; → potential.

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