Fr.: point de bifurcation
The point or moment in the evolution of a → dynamical system that occurs if a parameter passes through a critical point. At this point the system branches into any number of qualitatively new types of behavior.
Fr.: théorie de bifurcation
1) A theory which studies how, in certain nonlinear systems, there may be paths
and shifts in behavior dependent on small changes in circumstances or the current position
of the system.
bozorg (#), meh (#)
Fr.: grand, gros
Of considerable size, number, quantity, large.
M.E., northern England dialect, of unknown origin.
Bozorg, → large. Meh "great, large;" Mid.Pers. meh, mas; Av. maz-, masan-, mazant- "great, important," mazan- "greatness, majesty," mazišta- "greatest;" cf. Skt. mah-, mahant-; Gk. megas; L. magnus; PIE *meg- "great."
Meh Bâng (#), Big Bang (#)
Fr.: Big Bang
A theory which states that the Universe came into existence in an "instantaneous" event some 14 billion years ago. Matter was created in that initial event and as time has gone by the Universe has expanded and the contents evolved into the galaxies and stars and of today. The Big Bang is sometimes described as an "explosion." However, matter and energy did not erupt into a pre-existing space, since they came into being simultaneously with space and time.
→ big; bang "a sudden loud noise, as of an explosion" (probably of Scandinavian origin; akin to Icelandic banga "to hammer"). The term was coined by Fred Hoyle in 1950 in the course of discussions entitled "the Nature of the Universe" broadcasted by BBC. Hoyle's intention was a pejorative term in order to ridicule the theory which his own → steady-state theory contested.
Meh Bâng, from meh "great, large," → big, + bâng "voice, sound, clamour," (Mid.Pers. vâng, Av. vaocanghê "to declare (by means of speech"), vacah- "word," from vac- "to speak, say," cf. Mod.Pers. vâžé "word," âvâz "voice, sound, song," Skt. vakti "speaks, says," vacas- "word;" Gk. epos "word," L. vox "voice;" PIE base *wek- "to speak").
Big Bang model
model-e Meh Bâng, ~ Big Bang
Fr.: modèle du big bang
Big Bang nucleosynthesis (BBN)
haste-handâyeš-e Meh Bâng, ~ Big Bang
Fr.: nucléosynthèse de Big Bang
The production of → light elements, roughly three minutes after the → Big Bang when the temperature of the → Universe dropped from 1032 K to approximately 109 K. In a short time interval → protons and → neutrons collided to produce → deuterium. Most of the deuterium then fused with other protons and neutrons to produce → helium and a small amount of → tritium. The element → lithium 7 could also arise form the coalescence of one tritium and two deuterium nuclei. According to the Big Bang nucleosynthesis theory, roughly 25% of the mass of the Universe consists of helium. It also predicts about 0.01% deuterium, and even smaller quantities of lithium. These predictions depend critically on the → baryon-photon ratio. Same as → primordial nucleosynthesis.
Big Bang singularity
takini-ye Big Bang
Fr.: singularité du Big Bang
A hypothetical state of → infinite energy density representing an infinite → gravitational field and infinite → space-time curvature. The singularity arises from using Einstein's theory of → general relativity concerning gravity. We know, however, that when the density and heat become extremely large, quantum physics of gravity becomes important. Yet Einstein's equations ignore quantum effects. In other words, in certain extreme conditions, Einstein's equations do not apply.
Big Bang theory
negare-ye Meh Bâng, ~ Big Bang
Fr.: théorie du big bang
big blue bump
quz-e âbi-ye bozorg
Fr.: grande bosse bleue
The broad continuum feature dominating the optical-ultraviolet spectra of AGNs. Most current models attribute the big blue bump to thermal emission from an optically thick accretion disk.
Meh Romb, rombeš-e farjâmin
Fr.: big crunch
The state of extremely high density and temperature into which a closed → Universe would → collapse in the distant future. If the Universe has a mass density exceeding the critical threshold, then gravity will eventually halt the expansion and cause the Big Crunch.
→ big; crunch "to crush, grind, or tread noisily; the act or sound of crunching," alteration of craunch, possibly of imitative origin.
haft barâdarân (#), haftowrang (#), camce-ye bozorg (#)
Fr.: Grand Chariot
A group of seven stars, an → asterism, lying inside the Northern constellation → Ursa Major. They are: → Dubhe, → Merak, → Phad, → Megrez, → Alioth, → Mizar, and → Alkaid. The group is also known as the Plough in Great Britain.
→ big; dipper a popular U.S. name for the asterism known in Britain as The Plough or Charles' Wain, from dip O.E. dyppan "immerse," from P.Gmc. *dupjanan.
Haft barâdarân "the seven brothers," from haft "seven"
(Mid.Pers. haft, Av. hapta, cf. Skt. sapta, Gk. hepta,
L. septem, P.Gmc. *sebun, Du. zeven, O.H.G. sibun,
Ger. sieben, E. seven; PIE *septm)
+ barâdarân, plural of barâdar "brother"
(Mid.Pers. brad, bardar, O.Pers./Av. brātar-, cf. Skt. bhrátar-,
Gk. phrater, L. frater, P.Gmc. *brothar;
PIE base *bhrater- "brother").
Fr.: gros grain
A type of → interstellar dust grains with a size ranging from 150 to 1000 Å. Big grains consist of graphite and silicates. They are in → thermal equilibrium with the radiation field and their emission can be described by a modified → blackbody radiation following from → Kirchhoff's law.
Fr.: big rip
A cosmological hypothesis regarding the ultimate fate of the → Universe whereby in a far future galaxies and stellar systems would be torn apart due to the → accelerating expansion of the Universe depending on the kind of the → dark energy content of the Universe. According to this hypothesis, after the disruption of galaxies, stars, and planets even atoms might not be able to withstand the internal force of the expansion imposed by the dark energy.
→ big; M.E. rippen, origin obscure, cf. Frisian rippe "to tear, rip," M.Du. reppen, rippen "to pull, jerk," Swed. reppa, Dan. rippe "to tear, rip."
Meh "large, big," see under → big; gosast stem of gosastan "to tear, cut, break," from Mid.Pers. wisistan "to break, split," Av. saed-, sid- "to split, break," asista- "unsplit, unharmed," Skt. chid- "to split, break, cut off," PIE base *skei- "to cut, split," cf. Gk. skhizein "to split," L. scindere "to split," Goth. skaidan, O.E. sceadan "to divide, separate."
A → mapping f from a → set A onto a set B which is both an → injection and a → surjection. More explicitly, for every element b of B there is a unique element a of A for which f(a) = b. Also known as → bijective mapping.
From bi- + → injection.
Of or pertaining to a → bijection.
Fr.: application bijective
Same as → bijection.
Fr.: morphisme bijectif
Same as → isomorphism.
Having or providing two modes, methods, systems, etc., in particular having or occurring with two statistical modes.
bimodal star formation
diseš-e domod-e setâregân
Fr.: formation bimodale d'étoile
A concept of → star formation in which → high-mass stars and → low-mass stars form in different physical conditions involving different → molecular clouds. Following the pioneering suggestion of Herbig (1962), successive investigations have generally supported the idea that star formation proceeds bimodally with respect to stellar mass. The star formation rate appears to differ both spatially and temporally for low mass and → massive stars. This is of considerable importance for galactic evolution, since the low-mass stars lock up mass and are long-lived, low luminosity survivors to the present epoch, whereas massive stars are short-lived, recycle and enrich interstellar gas, and leave dark remnants while producing a high luminosity per unit of mass (Silk, J., 1988, in Galactic and Extragalactic Star Formation, p. 503, eds. R. E. Pudritz and M. Fich).
The quality or state of being → bimodal.