# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 19 Search : condition
 Abbe sine condition   بوتار ِ سینوس ِ آبه   butâr-e sinus-e AbbeFr.: condition des sinus d'Abbe   In → geometric optics, a condition for eliminating → spherical aberration and → coma in an → optical system. It is expressed by the relationship: sin u'/U' = sin u/U, where u and U are the angles, relative to the → optical axis, of any two rays as they leave the object, and u' and U' are the angles of the same rays where they reach the image plane. A system which satisfies the sine condition is called → aplanatic.Named after Ernst Karl Abbe (1840-1905), a German physicist; → sine; → condition. adiabatic initial conditions   بوتارهای ِ آغازین ِ بی‌دررو   butârhâ-ye âqâzin-e bidarrowFr.: conditions initiales adiabatiques   The assumption whereby the density fluctuations in the very → early Universe would be produced by compressing or decompressing of all components of a homogeneous Universe. The adiabatic initial conditions lead to coherent oscillations in the form of peaks in the → temperature anisotropy spectrum. See also → acoustic peak, → baryon acoustic oscillation.→ adiabatic; → initial; → condition. boundary conditions   بوتارها‌ی ِ کران، ~ کرانی   butârhâ-ye karân, ~ karâniFr.: conditions à la limite   1) Math: Restriction on the limits of applicability of an equation. In a differential equation, conditions that allow to fix the constant of integration and reach a unique solution. The number of boundary conditions necessary to determine a solution matches the order of the equation. 2) Physics: Conditions needed to determine the evolution of a system, given the physical laws.→ boundary; → condition. condition   بوتار   butârFr.: condition   1) Physics: The state of a physical system at a given time. Also called → physical condition. 2) Math: A premise, statement, or restriction upon which a mathematical result or consequence depends. → initial conditions; → boundary conditions.From O.Fr. condition, from L. condicionem (nom. condicio) "agreement, situation," from condicere "to speak with, talk together," from → com- "together" + dicere "to speak," from PIE *deik- "to point out;" cf. Av. daēs- "to show; assign; make known," Skt. dis- "to show, point toward," disati "shows," Gk. deiknunai "to show," O.H.G. zeigon, Ger. zeigen "to show," E. token "indication, sign."Butâr, from Mid.Pers. but past tense stem of butan Mod.Pers. budan "to be, become," → exist, + -âr noun suffix (as in raftâr, jostâr, goftâr, kerdâr). conditional   بوتاری، بوتارمند   butâri, butârmandFr.: conditionnel   1) Imposing, containing, subject to, or depending on a condition or conditions; not absolute; made or allowed on certain terms. 2a) Logic: (of a proposition) Asserting that the existence or occurrence of one thing or event depends on the existence or occurrence of another thing or event. 2b) (of a → syllogism) Containing at least one → conditional proposition as a → premise (Dictionary.com). 2c) The "if ... then" relation.→ condition; → -al. conditional introduction   اندرهازش ِ بوتاری   andarhâzeš-e butâriFr.: introduction conditionnelle   A derivation rule that begins with an → assumption in a → subproof and allows for deriving a conditional outside the subproof. The derived conditional consists of the assumed proposition as the → antecedent and the derived conclusion in the subproof as the → consequent.→ conditional; → introduction. conditional probability   شوانایی ِ بوتاری   šavânâyi-ye butâriFr.: probabilité conditionnelle   Of an event B in relationship to an event A, the probability that event B occurs given that event A has already occurred. The notation for conditional probability is P(B|A), read as the probability of B given A: P(B|A) = P(A ∩ B)/P(A). → Bayes' theorem. conditional proof   آوین ِ بوتاری   âvin-e butâriFr.: preuve conditionnelle   A → proof in which one assumes the → truth of one of the → premises to show that if that premise is true then the → argument is → valid.→ conditional; → proof. conditional proposition   گزاره‌ی ِ بوتاری   gozâre-ye butâriFr.: proposition conditionelle   A compound → proposition in which one → clause asserts something as true provided that the other clause is true. A conditional statement consists of two parts, a hypothesis in the "if" clause and a conclusion in the "then"clause. For instance, "If it rains, then they cancel school." It rains is the hypothesis. "They cancel school" is the conclusion. The clause following if is traditionally called the → antecedent, whereas the clause following then is called the → consequent. Dirichlet condition   بوتار ِ دیریکله   butâr-e DirichletFr.: condition de Dirichlet   One of the following conditions for a → Fourier series to converge: 1) The function f(x) is defined and single valued, except possibly at a finite number of points in the interval -π, +π. 2) f(x) has a period of 2π. 3) f(x) and f'(x) are → piecewise continuous functions on -π, +π. Then, the Fourier series converges to: (a) f(x) if x is a point of continuity. (b) (f(x + 0) + f(x - 0))/2, if x is a point of discontinuity.Named after Peter Gustav Lejeune Dirichlet (1805-1859), German mathematician who made valuable contributions to → number theory, → analysis, and → mechanics; → condition. Gamow condition   بوتار ِ گاموف   butâr-e GamowFr.: condition de Gamow   The constraint on the → baryon number density at T ~ 109 K in the early → expanding Universe. Gamow recognized that a key to the element buildup is the reaction n + p ↔ d + γ. Deuterium needs to be produced in sufficient abundance for higher elements to form, but if all → neutrons are immediately locked up into → deuterium, no higher elements can form either. The Gamow condition is expressed by nb<σv>t ~ 1, where nb is the baryon number density, σ is the cross section for the reaction at relative → velocity v, and t the expansion time-scale for the → Universe. This means that the time-scale for the above reaction is comparable to the expansion time. From this condition the baryon number density at the start of element buildup is found to be nb ~ (σvt)-1 ~ 1018 cm-3 at T = 109 K (P. J. E. Peebles, 2013, Discovery of the Hot Big Bang: What happened in 1948, arXiv.1310.2146). initial conditions   بوتارهای ِ آغازین   butârhâ-ye âqâzinFr.: conditions initiales   1) Conditions at an initial time t = t0 from which a physical system or a given set of mathematical equations evolves. 2) Meteo.: A prescription of the state of a → dynamical system at a specified time; for all subsequent times, the → equation of motion and → boundary conditions determine the state of the system.→ initial; → condition. jump conditions   بوتارهای ِ جهش   butârhâ-ye jahešFr.: conditions de saut   Very different values of pressure and density (or temperature or energy) across a shock wave.→ jump; → condition. MHD condition   بوتار ِ MHD   butâr-e MHDFr.: condition MHD necessary and sufficient conditions   بوتارهای ِ بایسته و بسنده   butârhâ-ye bâyesté o basandéFr.: conditions nécessaire et suffisante   If event A must occur for event B to occur, then it is said that A is → necessary for B. If event A may cause B but there could be some other cause as well, then it is said that A is sufficient to cause B. See also → if and only if (iff).→ necessary; → and; → sufficient; → condition. physical condition   بوتار ِ فیزیکی   butâr-e fizikiFr.: condition physique   The state of a → physical system regarding its temperature, density, pressure, etc. at a given time.→ physical; → condition. Rankine-Hugoniot conditions   بوتارهای ِ رانکین-هوگونیو   butârhâ-ye Rankine-HugoniotFr.: conditions de Rankine-Hugoniot   Hydrodynamics → conservation laws (which can be extended to → magnetohydrodynamics, MHD) which describe the physical conditions of material across a → shock front. A fluid is completely described by its velocity, density, pressure, specific heat ratio, and magnetic field (in the MHD case). Mass, momentum, and energy fluxes are conserved in the shock, leading to the Rankine-Hugoniot relations. Also called Rankine-Hugoniot jump conditions. See also → jump condition.Named after William John Rankine, → Rankine scale, and Pierre Henri Hugoniot, → Hugoniot curve; → condition. Sakharov conditions   بوتارهای ِ ساخاروف   butârhâ-ye SakharovFr.: conditions de Sakharov   The three conditions that are necessary for the generation of a → baryon asymmetry in the → early Universe. These conditions are: 1) The → baryon number should not be → conserved. 2) The → charge conjugation and → CP symmetry should be → violated, and 3) Departure from → thermal equilibrium.Named after Andrei Sakharov (1921-1989), who in 1967 described these three minimum conditions (A. D. Sakharov, 1967, Zh. Eksp. Teor. Fiz. Pis'ma 5, 32; 1967, JETP Lett. 91B, 24); → condition. unconditional   نابوتاری، نابوتارمند   nâbutâri, nâbutârmandFr.: inconditionnel   Not limited by conditions; absolute.→ un-; → conditional.