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Hamiltonian operator âpârgar-e Hamilton Fr.: opérateur hamiltonien The dynamical operator in → quantum mechanics that corresponds to the → Hamiltonian function in classical mechanics. → Hamiltonian function; → operator. |
Hawking temperature damâ-ye Hawking Fr.: température de Hawking The temperature inferred for a → black hole based on the → Hawking radiation. For a → Schwarzschild black hole, one has T_{H} = ħc^{3}/(8πGMk) where ħ is the → reduced Planck's constant, c is the → speed of light, G is the → gravitational constant, M is the mass, and k is → Boltzmann's constant. The formula can approximately be written as: T_{H}≅ 6.2 x 10^{-8} (Msun/M) K. Thus radiation from a solar mass black hole would be exceedingly cold, about 5 x 10^{7} times colder than the → cosmic microwave background. Larger black holes would be colder still. Moreover, smaller black holes would have higher temperatures. A → mini black hole of mass about 10^{15} g would have T_{H}≅ 10^{11} K. → Hawking radiation; → temperature. |
Hayashi temperature damâ-ye Hayashi Fr.: température de Hayashi The minimum → effective temperature required for a → pre-main sequence star of given mass and radius to be in → hydrostatic equilibrium. This temperature delimits the boundary of the → Hayashi forbidden zone. → Hayashi track; → temperature. |
Henry Draper system râžmân-e Henry Draper Fr.: système de Henry Draper A catalog of stars in which every star is classified by its stellar spectrum. This system is named for the astronomer Henry Draper, but was cataloged by Annie J. Cannon (225,300 stars), and later extended by Margaret W. Mayall. Henry Draper (1837-1882), an American pioneer of astronomical spectroscopy who established the observing techniques and program for the work that would bear his name when published, seven years after his early death; → system. |
Hermitian operator âpârgar-e Hermiti Fr.: opérateur hermitien An operator A that satisfies the relation A = A^{*}, where A^{*} is the adjoint of A. → Hermitian conjugate. → Hermitian conjugate; → operator. |
Hertz experiment âzmâyeš-e Hertz (#) Fr.: expérience de Hertz A laboratory experiment carried out by Heinrich Hertz in 1888 to generate and detect → electromagnetic waves for the first time. It involved a high voltage power source, consisting of two → capacitors, each provided with a conducting rod. The rods were separated by a small → spark gap and connected to an → induction coil. When the electrodes were raised to a sufficiently high → potential difference, a spark passed across the gap, and an oscillating discharge took place. A group of waves with a wavelength of a few meters were emitted at each discharge. A wire loop provided with a detecting spark gap, held away from the oscillating sparks, produced sparks upon arrival of the oscillating electric and magnetic fields. → hertz (Hz); → experiment. |
Hesperian era dowrân-e hesperisi Fr.: ère hespérienne The Martian geologic era after the Noachian Era which lasted from about 3500 million to 2500 million years ago. During this period Martian climate began to change to drier, dustier conditions. Water that flowed on the Martian surface during the Noachian Era may have frozen as underground ice deposits, and most river channels probably experienced their final flow episodes during this era. → Noachian era; → Amazonian era. Named after the Martian plains of Hesperis; → era. |
Hesperus setâre-ye šâmgâh (#) Fr.: étoile du soir An → evening star, especially the planet Venus in its appearance as the evening star. M.E., from L., from Gk. hesperos "evening, western;" → west. Setâre-ye šâmgâh "evening star," from setâré→ star + šâmgâh "evening," from šâm "evening, evening meal" + gâh "time." The first component, šâm, from Mid.Pers. šâm "evening meal, supper," from Av. xšāfnya- "evening meal," from Av. xšap-, xšapā-, xšapan-, xšafn- "night" (O.Pers. xšap- "night," Mid.Pers. šap, Mod.Pers. šab "night"); cf. Skt. ksap- "nigh, darkness;" Hittite ispant- "night." The second component gâh "time," Mid.Pers. gâh, gâs "time," O.Pers. gāθu-, Av. gātav-, gātu- "place, throne, spot;" cf. Skt. gâtu- "going, motion; free space for moving; place of abode;" PIE *gwem- "to go, come." |
historical supernova abar-novâ-ye târixi, abar-now-axtar-e ~ (#) Fr.: supernova historique A supernova event recorded in the course of history before the invention of the telescope. The well recorded supernovae of this small group are SN 185, SN 1006, SN 1054 (→ Crab Nebula), SN 1181, SN 1572 (→ Tycho's star), and SN 1604 (→ Kepler's star). → historical; → supernova. |
hyper- 1) abar- (#); 2) hiper- (#) Fr.: hyper- A prefix appearing in loanwords from Greek meaning: From Gk. hyper, preposition and adverb, "over, beyond, overmuch, above;" cognate with L. super- and Pers. abar-, as below. 1) Mid.Pers. abar; O.Pers.
upariy "above; over, upon, according to;" Av. upairi "above, over,"
upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;"
L. super-; O.H.G. ubir "over;" PIE base *uper "over." |
hyperbola hozluli (#) Fr.: hyperbole A two-branched open curve, a type of conic section, defined as the intersection between a right circular conical surface and a plane which cuts through both halves of the cone. From Gk. hyperbole "excess, exaggeration" literally "a throwing beyond," from hyperballein "to throw over or beyond," from → hyper- "beyond" + bol-, nom. stem of ballein "to throw." Hozluli, loanword from Ar. |
hyperbolic hozluli (#) Fr.: hyperbolique Of or pertaining to a → hyperbola. |
hyperbolic cosine kosinus-e hozluli Fr.: cosinus hyperbolique A function, denoted cosh x, defined for all real values of x, by the relation: cosh x = (1/2) (e^{x} + e^{-x}). → hyperbolic; → cosine. |
hyperbolic function karyâ-ye hozluli Fr.: fonction hyperbolique Any of the six functions sinh, cosh, tanh, coth, csch, and sech that are related to the → hyperbola in the same way the → trigonometric functions relate to the → circle. Many of the formulae satisfied by the hyperbolic functions are similar to corresponding formulae for the trigonometric functions, except for + and - signs. For example: cosh^{2}x - sinh^{2}x = 1. See also: → hyperbolic cosine, → hyperbolic sine. Hyperbolic functions were first introduced by the Swiss mathematician Johann Heinrich Lambert (1728-1777). → hyperbolic; → function. |
hyperbolic orbit madâr-e hozluli (#) Fr.: orbite hyperbolique An orbit that is an open curve whose ends get wider apart at any rate between that of an ellipse and a straight line. Some comets' orbits become hyperbolic through the gravitational influence of a planet the comet passes near. → hyperbolic; → orbit. |
hyperbolic sine sinus-e hozluli Fr.: sinus hyperbolique A function, denoted cosh x, defined for all real values of x, by the relation: cosh x = (1/2) (e^{x} - e^{-x}). → hyperbolic; → sine. |
hyperbolic space fazâ-ye hozluli (#) Fr.: espace hyperbolique A three-dimensional space whose geometry resembles that of a saddle-shaped surface and is said to have negative curvature. → hyperbolic; → space. |
hyperboloid hozlulivâr (#) Fr.: hyperboloïde A surface or body obtained by rotating a hyperbola about its axis of symmetry. Hyperboloid, from hyperbol(a) + → -oid a suffix meaning "resembling, like." Hozlulivâr, from hozluli, → hyperbola, + -vâr a suffix of similarity. |
hyperfine abar-nâzok Fr.: hyperfine Extremely fine or thin, especially of a → spectral line split into two or more very thin components. → hyperfine structure; → hyperfine transition. → hyper-, → fine structure. |
hyperfine structure sâxtâr-e abar-nâzok (#) Fr.: structure hyperfine In spectroscopy, the → splitting of a spectral line into a number of very thin components. It results from a small perturbation in the energy levels of atoms or molecules due to the magnetic dipole-dipole interaction arising from the interaction of the nuclear → magnetic moment with the → spin of the electron. It can be observed only at high spectral dispersion. → fine structure. |
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