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Lorentz Lorentz Fr.: Lorentz Contraction of the full name of Hendrik Antoon Lorentz (1853-1928), a Dutch physicist, who made important contribution to physics. He won (with Pieter Zeeman) the Nobel Prize for Physics in 1902 for his theory of electromagnetic radiation, which, confirmed by findings of Zeeman, gave rise to Albert Einstein's special theory of relativity. |
Lorentz contraction terengeš-e Lorentz Fr.: contraction de Lorentz The decrease in the length of a body moving in the direction of its length as measured by an observer situated in that direction. The shortening factor is [1 - (v/c)^{2}]^{1/2}, where v is the relative velocity and c light speed. → Lorentz; → contraction. |
Lorentz factor karvand-e Lorentz Fr.: facteur de Lorentz In → special relativity, an important parameter which appears in several equations, including → time dilation, → length contraction, and → relativistic mass. It is defined as γ = 1 / [1 - (v/c)^{2}]^{1/2} = dt/dτ, where v is the velocity as observed in the reference frame where time t is measured, τ is the proper time, and c the → velocity of light. Same as Lorentz γ factor. |
Lorentz force niru-ye Lorentz (#) Fr.: force de Lorentz The force acting upon a → charged particle as it moves in a → magnetic field. It is expressed by F = q.v x B, where q is the → electric charge, v is its → velocity, and B the → magnetic induction of the field. This force is perpendicular both to the velocity of the charge and to the magnetic field. The magnitude of the force is F = qvB sinθ, where θ is the angle between the velocity and the magnetic field. This implies that the magnetic force on a stationary charge or a charge moving parallel to the magnetic field is zero. The direction of the force is given by the → right-hand rule. |
Lorentz invariance nâvartâyi-ye Lorentz Fr.: invariance de Lorentz Of a physical law, invariance with respect to a → Lorentz transformation. → Lorentz; → invariance. |
Lorentz resonance bâzâvâyi-ye Lorentz Fr.: résonance de Lorentz A repeated electromagnetic force on an electrically charged ring particle, nudging the particle in the same direction and at the same point in its orbit. Lorentz resonances are especially important for tiny ring particles whose charge-to-mass ratio is high and whose orbit periods are a simple integer fraction of the rotational period of the planet's magnetic field (Ellis et al., 2007, Planetary Ring Systems, Springer). |
Lorentz transformation tarâdis-e Lorentz Fr.: transformation de Lorentz A set of linear equations that expresses the time and space coordinates of one → reference frame in terms of those of another one when one frame moves at a constant velocity with respect to the other. In general, the Lorentz transformation allows a change of the origin of a coordinate system, a rotation around the origin, a reversal of spatial or temporal direction, and a uniform movement along a spatial axis. If the system S'(x',y',z',t') moves at the velocity v with respect to S(x,y,z,t) in the positive direction of the x-axis, the Lorentz transformations will be: x' = γ(x - vt), y' = y, z' = z, t' = γ [t - (vx/c^{2})], where c is the → velocity of light and γ = [1 - (v/c)^{2}]^{-1/2}. For the special case of velocities much less than c, the Lorentz transformation reduces to → Galilean transformation. → Lorentz; → transformation. |
Lorentzian profile farâpâl-e Lorentzi Fr.: profil lorentzien A spectral profile in which the intensity distribution follows a specific mathematical function (Lorentz or Cauchy probability). Compared to the normal or Gaussian profile, Lorentzian has a pointed peak and more important wings. |
Lorimer burst belk-e Lorimer Fr.: sursaut Lorimer, impulsion ~ The first ever discovered → fast radio burst. It was done during a search of archival data from a 1.4-GHz survey of the → Magellanic Clouds using the multi-beam receiver on the 64-m Parkes Radio Telescope in Australia. D. R. Lorimer et al., 2007, Science, 318, 777; → burst. |
Loschmidt's number adad-e Loschmidt Fr.: nombre de Loschmidt The number of molecules in 1 cm^{3} of an ideal gas (2.687 x 10^{19} per cm^{3}). Joseph Loschmidt (1821-1895), Austrian physicist. |
loss dastraft Fr.: perte In physics, a measure of the energy, mass, or other physical quantities lost in a system, by conversion or external effects. From O.E. los "loss, destruction," from P.Gmc. *lausa, from PIE base *leu- "to loosen, divide, cut apart, untie, separate" (cf. Gk. lyein "to loosen, untie, slacken," lysus "a loosening;" L. luere "to loose, release, atone for;" Skt. lunati "cuts, cuts off," lavitram "sickle;" Pers. las "loose," lâ "slit, cut;" → analysis). Dastraft, literally "gone from hand," from dast "hand" (Mid.Pers. dast; O.Pers. dasta-; Av. zasta-; cf. Skt. hásta-; Gk. kheir; L. praesto "at hand;" Arm. jern "hand;" Lith. pa-žastis "arm-pit;" PIE *ghes-to-) + raft p.p. of raftan "to go, elapse, glide by, depart" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack"). |
loud boland (#) Fr.: fort, sonore, bruillant High in volume of sound. M.E., O.E. hlud "making noise, sonorous" (cf. M.Du. luut, Du. luid, O.H.G. hlut, Ger. laut "loud"), from PIE *klutos- (cf. Skt. sruta-, Gk. klytos "heard of, celebrated," Arm. lu "known." Boland, → high. |
loudness bolandi-ye sedâ (#) Fr.: sonie, force The magnitude of the sensation produced by a sound wave when it reaches the ear. The loudness of a sound depends upon the effective → acoustic pressure and → frequency. The basis of loudness scales is the → Weber-Fechner law. |
loudspeaker bolandgu (#) Fr.: haut-parleur A device in which electric signals are converted into audible sound. → loud, + agent noun of speak M.E. speken, O.E. specan, variant of sprecan "to speak" (cf. O.S. sprecan, M.Du. spreken, O.H.G. sprehhan, Ger. sprechen "to speak," O.N. spraki "rumor, report"). Bolandgu, from boland, → loud + gu agent noun of goftan "to speak, to say," from Mid.Pers. guftan "to say, tell, utter;" O.Pers. gaub- "to say." |
low 1) kam (#), keh (#); 2) kutâh (#), pâyin (#) Fr.: bas, faible 1) Below the average or expected degree, amount, or intensity.
Having or containing a relatively small amount. From M.E. lah, from O.N. lagr "low," from P.Gmc. *lægaz (cf. O.Fris. lech, Du. laag, Ger. läge "low"), literally "that which is lying flat;" related to E. lie (v.). Kam "little, few; deficient, wanting; scarce,"
from Mid.Pers. kam "little, small, few," O.Pers./Av. kamna- "small, few." |
low redshift keh sorxkib Fr.: faible décalage vers le rouge A redshift characterizing a near-by receding object. |
low resolution keh vâgošud Fr.: faible résolution The quality of an instrument that lacks sufficient resolution for a specific observation. This is a relative quality, but presently a resolution below about 1 arcsecond. → low; → resolution. |
low surface brightness galaxy (LSBG) kahkešân bâ deraxšandegi-ye ruye-yi-ye kam Fr.: galaxie à faible brillance de surface A member of a particularly faint population of galaxies with a central → surface brightness below the brightness of the background sky. The central regions of many of them resemble a → dwarf galaxy, but most of the mass is contained in a large gaseous disk of low density that is observable only with long-exposure optical images or at radio wavelengths. Some are as massive as a large → spiral galaxy, for example Malin 1. The proportion of LSBGs relative to normal galaxies is unknown. They may however represent a significant fraction of mass in the Universe. LSBGs are thought to be primitive systems because they have total masses similar to normal galaxies, but have typically converted less than 10% of their gas into stars. Spiral LSBGs do not obey → Freeman's law. → low; → surface; → brightness; → galaxy. |
low tide owpas (#), jazr (#) Fr.: marée basse The state of the → tide when at its lowest level. Owpas, from Persian Gulf dialects, literally "backward water," from ow,
variant of âb, → water, + pas
"→ back, behind." |
low water owpas, jazr Fr.: marée basse Also known as → low tide. |
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