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redshift space distortion cowlegi-ye fazâ-ye sorx-kib Fr.: distorsion dûe aux vitesses particulières sur la ligne
de visée The distortion observed in → redshift space of → galaxy clusters caused by peculiar velocities of the members (→ peculiar velocity). In a perfectly homogeneous → Friedmann-Lemaitre Universe the redshifts would accurately measure radial distances from the observer, and the mapping from real space to redshift space would simply be an identity. In an inhomogeneous Universe the peculiar velocities associated with any inhomogeneous structure will introduce a distortion in this mapping (N. Kaiser, 1987, MNRAS 227, 1). See also: → fingers of God, → Kaiser effect. → redshift; → space; → distortion;. |
redshift survey bardid-e sorx kib Fr.: relevé de décalages vers le rouge A survey of a large region of the sky to measure the redshifts of all the galaxies down to a certain limiting magnitude. |
redshift-distance relation bâzâneš-e sorxkib-durâ Fr.: relation décalage vers le rouge-distance The correlation, first established by E. Hubble, between the cosmological recession velocities of galaxies and their distances. |
redshifted line xatt-e sorx kibideh Fr.: raie décalée vers le rouge A spectral line whose wavelength does not coincide with its theoretical value and is shifted toward longer wavelengths. |
reduce 1) bâzhâxtan, bâzhâzidan; 2) kâstan Fr.: réduire 1) To bring to a certain state, condition, arrangement, etc. M.E. reducen "to lead back," from O.Fr. reducer, from L. reducere, from → re- "back" + ducere "to bring, to lead." From bâz-, → re- +
Mid.Pers. hâxtan, hâzidan
"to lead, guide, persuade," Av. hak-, hacaiti "to attach oneself to, to join," cf.
Skt. sacate "accompanies, follows," Gk. hepesthai
"to follow," L. sequi "to follow;" PIE *sekw- "to follow." |
reduced mass jerm-e bâhâzidé Fr.: masse réduite The "effective" → inertial mass appearing in the → two-body problem of → Newtonian mechanics. The reduced mass is a quantity which allows the two-body problem to be solved as if it were a one-body problem. For the masses m_{1} and m_{2}, it is given by the ratio μ = m_{1}m_{2} / (m_{1} + m_{2}). The value of μ is generally smaller than m_{1} and m_{2}. The larger the difference between the two masses, the closer μ will be to the smaller mass. If the particles are of equal mass, μ is half the mass of either. |
reduced Planck constant pâyâ-ye Planck-e bâzhâzidé Fr.: constante de Planck réduite The → Planck constant divided by 2π and denoted ħ, pronounced h-bar. Also called the → Dirac constant. Reduced, p.p. of → reduce; → Planck's constant. |
reduced Planck's constant pâyâ-ye Planck-e bâzhâzidé Fr.: constante de Planck réduite |
reducing agent konešgar-e bâzhâzandé Fr.: réducteur A substance which removes → oxygen from, or adds → hydrogen, to another substance. In the more general sense, one which loses electrons. Also called → reductant. |
reducing atmosphere javv-e bâzhâzandé, havâsepehr-e ~ Fr.: atmosphère réductrice 1) An atmospheric condition in which oxidation is prevented by removal
of oxygen and other oxidating gasses or vapours. Usually nitrogen or
hydrogen gas is used in order to produce specific effects, e.g. on
ceramic wares being fired. Reducing verbal adj. of → reduce; → atmosphere. |
reductant bâzhâzandé Fr.: réducteur Same as → reducing agent. Agent noun from → reduce. |
reductio ad absurdum bâzhâzeš bé yâvé Fr.: raisonnement par l'absurde Logic, Math.: A method of → reasoning in which one assumes some statement to be → true and from that → assumption proceeds to deduce a logical → absurdity and hence to a conclusion that the original assumption must have been → false. L. reductio ad absurdum "reduction to absurdity," → reduction; → absurd. |
reduction bâzhâzeš Fr.: réduction 1) In → data processing, the transformation of data from
a "raw" form to some usable form. Verbal noun of → reduce. |
redundancy afzun-âyi Fr.: redondance The fact of repeating or duplicity. From L. redundantia "an overflowing, excess," from redundare "to flow back, overflow, be excessive," from → re- "again" + undare "rise in waves," from unda "a wave." Afzun-âyi "redundancy, superabounding," from afzun "more, greater; more ample," from afzudan "to add, increase" (Mid.Pers. abzudan "to increase, grow;" O.Pers. abijav- "to increase, add to, promote," from abi-, aiby- "in addition to; to; against" + root jav- "press forward;" Av. gav- "to hasten, drive;" Sk. jav- "to press forward, impel quickly, excite," javate "hastens") + âyi verbal noun of ây- present stem of âmadan "to come, arrive, become" (Av. ay- "to go, to come," aēiti "goes;" O.Pers. aitiy "goes;" Skt. e- "to come near," eti "arrival;" L. ire "to go;" Goth. iddja "went," Lith. eiti "to go;" Rus. idti "to go"). |
Rees-Sciama effect oskar-e Rees-Sciama Fr.: effet de Rees-Sciama The → Sachs-Wolfe effect in which the calculations are extended to nonlinear mass concentrations. In the non-linear regime of large-scale → structure formation the → gravitational potential changes with time, and photons climb out of a → potential well slightly different from the one that they fell into. Therefore, nonlinear density fluctuations produce extra evolution of the potentials against the background expansion. On large scales, the nonlinear contribution to the full ISW effect is expected to be dominated by the linear ISW effect in a Universe with → cosmological constant (Seljak, 1996, ApJ 460, 549). Martin J. Rees (1942-) & Dennis W. Sciama (1926-1999), 1968, Nature 217, 511; → effect. |
refer bâzbordan (#) Fr.: référer 1) To direct for information or anything required. M.E. referren, from L. referre "to bring back," from → re- "back" + ferre "carry, bear," cognate with Pers. bordan "to carry, bear," as below. Bâzbordan, literally "to bring back," from bâz "back," → re- + bordan "to carry, bear" (Mid.Pers. burdan, O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive)," Skt. bharati "he carries," Gk. pherein, L. fero "to carry;" PIE base *bher- "to carry"). |
reference bâzbord (#) Fr.: référence 1) An act or instance of referring. Verbal noun of → refer. |
reference ellipsoid beyzivâr-e bâzbord Fr.: ellipsoïde de référence A mathematically defined surface that approximates the Earth's shape, which is basically a sphere "flattened" at its poles. The length of one of the axes at the Equator is chosen so that the ellipsoid coincides at this latitude with the mean sea level. It is the first-order definition of the non-spherical shape of the Earth as an ellipsoid of revolution. To first order, it accounts for over 90% of the → geoid. |
reference frame cârcub-e bâzbord Fr.: système de référence A set of axes to which positions and motions in a system can be referred. Same as → frame of reference. |
reference source xan-e bâzbord Fr.: source de référence An astronomical source in a field used as a reference for the detection of another object, astrometry, etc. |
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