1) pergâli; 2) vâpeš-e pergalandé
Fr.: 1) performatif; d'interprétation; 2) performativité
A sentence or expression which is not only describing a given reality, but actually does or accomplishes something. For example "I now declare you husband and wife" (when uttered by the authorized officiator during a marriage ceremony).
Fr.: interprète, acteur, artiste
1) Someone who performs in front of an audience, for example an actor or musician.
Planck's blackbody formula
disul-e siyah jesm-e Planck
Fr.: formule du corps noir de Planck
A formula that determines the distribution of intensity of radiation that prevails under conditions of thermal equilibrium at a temperature T: Bv = (2hν3 / c2)[exp(hν / kT) - 1]-1 where h is Planck's constant and ν is the frequency.
Fr.: déformation plastique
Fr.: formalisme post-newtonien
An approximate version of → general relativity that applies when the → gravitational field is → weak, and the matter → velocity is → small. Post-Newtonian formalism successfully describes the gravitational field of the solar system. It can also be applied to situations involving compact bodies with strong internal gravity, provided that the mutual gravity between bodies is weak. It also provides a foundation to calculate the → gravitational waves emitted by → compact binary star systems, as well as their orbital evolution under radiative losses. The formalism proceeds from the Newtonian description and then, step by step, adds correction terms that take into account the effects of general relativity. The correction terms are ordered in a systematic way (from the largest effects to the smallest ones), and the progression of ever smaller corrections is called the → post-Newtonian expansion.
Fr.: formalisme de Press-Schechter
A mathematical analysis, based on → self-similarity, used to predict the → mass function of spherically collapsing → dark matter halos. The formalism assumes that the fraction of mass in halos more massive than M is related to the fraction of the volume in which the smoothed initial density field is above some threshold δcρ, where ρ is the average density of the Universe, with the volume encompassing a mass larger than M. A variety of smoothing → window functions and thresholds have been argued, but the most common is a top-hat window in real space and δc≅ 1.69. The Press-Schechter formalism provides a relatively good fit to the results of numerical simulations in cold dark matter theories.
First described by William H. Press and Paul Schechter's paper (1974, ApJ 187, 425); → formalism.
Fr.: formule quadratique
A formula relating the unknown part of a → quadratic equation to the known parts.
Fr.: information quantique
The science concerned with the transmission, storage, and processing of information using quantum mechanical systems. It exploits the notion of → quantum entanglement between systems and joins several fields of knowledge, mainly quantum physics, information, computation, and probability.
1) bâzdisi; 2) bâzdisida,
Fr.: 1) réforme; réformer
1) (n.) The improvement, amendment, or reorganization of something
that is considered to be wrong, ineffective, or unsatisfactory;
e.g. calendar reform.
From M.E. reformen, from M.Fr. reformer, from O.Fr., from L. reformare "to form again, change, alter," from → re- "again" + formare "to form," from forma "form, mold, shape, case," origin unknown.
1) Bâzdisi, from bâz- "again," → re-, +
dis, disé "form, appearance," (variants -diz, -diš (tandis
"body form, like a body; effigy; statute;" mâhdis "moon-like;"
šabdiz "night color; a horse of
dark rusty color;" andiš- "to think, contemplate"); Mid.Pers.
dêsag "form, appearance," dêsidan
"to form, build;" Av. daēs- "to show," daēsa- "sign, omen;"
cf. Skt. deś- "to show, point out;" PIE *deik- "to show"
(cf. Gk. deiknumi "to show,"
dike "manner, custom;" L. dicere "to utter, say;" O.H.G. zeigon,
Ger. zeigen "to show;" O.E. teon "to accuse," tæcan "to teach")
+ -i noun suffix.
Fr.: formule de Rydberg
A formula, used in atomic physics, which describes the wavelengths or frequencies of light in various series of related spectral lines, such as those emitted by hydrogen atoms.
semiempirical binding energy formula
disul-e nime-ârvini-ye kâruž-e bandeš
Fr.: formule semi-empirique de l'énérgie de liaison
Same as → Weizsacker formula.
sequential star formation
diseš-e peyâye-yi-e setâré
Fr.: formation séquentielle d'étoiles
The formation of second-generation stars in a → molecular cloud, as triggered by the presence of → massive stars. The observation that some nearby → OB associations contain distinct, spatially separate subgroups of → OB stars in a sequence of monotonically changing age led Blaauw (1964, ARA&A 2, 213) to suggest that star formation in fact occurs in sequential bursts during the lifetimes of the corresponding molecular clouds. The first quantitative model of this mechanism was presented by Elmegreen and Lada (1977, ApJ 214, 725), who showed that the powerful ultraviolet photons of the massive star create an → ionization front which advances in the molecular cloud and is preceded by a → shock front. The compressed neutral gas lying between the ionization and shock fronts is gravitationally unstable and collapses in time-scales of a few million years to form a new generation of massive stars. The propagation of successive births of OB groups would produce a chain of associations presenting a gradient of age. Elmegreen and Lada estimated the propagation velocity to be 5 km s-1. For a region with a length larger than 100 pc, this would imply an age difference of the order of 20 million years between the extremities. See also → stimulated star formation, → triggered star formation; → collect and collapse model.
Fr.: transformation de similarité
1) A transformation that preserves angles and changes all distances in the same ratio.
specific star formation rate (sSFR)
nerx-e âbize-ye diseš-e setâregân
Fr.: taux de formation d'étoiles spécifique
Star formation rate per unit → mass. More specifically, the → star formation rate in a galaxy divided by the → stellar mass of the galaxy. Observations of galaxies over a wide range of → redshifts suggest that the slope of the SFR-M* relation is about unity, which implies that their sSFR does not depend strongly on stellar mass. Specific star formation rates increase out to z ~ 2 and are constant, or perhaps slowly increasing, from z = 2 out to z = 6, though with a large scatter, sSFR ~ 2-10 Gyr-1 (Lehnert et al., 2015, A&A 577, A112, and references therein).
Fr.: formation d'étoiles
The process by which dense parts of molecular clouds collapse into a ball of plasma to form a star. As a branch of astronomy, star formation includes the study of the interstellar medium and molecular clouds as precursors to the star formation process as well as the study of young stellar objects.
star formation efficiency (SFE)
kârâyi-ye diseš-e setâré
Fr.: efficacité de formation d'étoiles
star formation history
târix-e diseš-e setâré
Fr.: histoire de formation d'étoiles
The → star formation rate as a function of time.
star formation quenching
osereš-e diseš-e setâregân
Fr.: assèchement de formation d'étoiles
The premature termination of star formation process in some galaxies. The ultimate quenching of star formation is caused by stripping of the gas reservoir which will finally turn into stars. A wide variety of mechanisms have been proposed to provide quenching. For example, → major mergers can transform spiral galaxies into ellipticals, and may also quench future star formation by ejecting the → interstellar medium from the galaxy via starburst, → active galactic nucleus, or shock-driven winds. In rich clusters, where merging is less efficient because of the large relative velocities of galaxies, rapid encounters or fly-bys may cause the formation of a bar and growth of a spheroidal component instead of larger scale star formation. Also, cold gas can be stripped out of the galaxy both by tidal forces and ram pressure in the intracluster medium. Similarly, the hot halo that provides future fuel for cooling and star formation may be efficiently stripped in dense environments, thus quenching further star formation (see, e.g., Kimm et al., 2009, MNRAS 394, 1131, arXiv:0810.2794).
star formation rate
nerx-e diseš-e setâré
Fr.: taux de formation d'étoiles
The rate at which a molecular cloud or a galaxy is currently converting gas into stars. It is given by the ratio of the number of stars to the star formation time-scale.