An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 16 Search : formal
conformal
  همدیس   
hamdis

Fr.: conforme   

Math.: Of, pertaining to, or specifying a mapping of a surface upon another surface so that all angles between intersecting curves remain unchanged.

con- + → form + → -al.

conformal compactification
  همپکانش ِ همدیس   
hampakâneš-e hamdi

Fr.: compactification conforme   

A mapping of an infinite → space-time onto a finite one that may make the far away parts of the former accessible to study. The technique invented by Penrose defines an equivalence class of → metrics, gab being equivalent to ĝab = Ω2gab, where Ω is a positive scalar function of the space-time that modifies the distance scale making the asymptotics of the physical metric accessible to study.

conformal; → compactification.

conformal mapping
  همتایش ِ همدیس   
hamtâyeš-e hamdis

Fr.: application conforme   

A continuous mapping u = f(x) of a domain D in an n-dimensional Euclidean space (n≥ 2) into the n-dimensional Euclidean space is called conformal at a point x0D if it has the properties of constancy of dilation and preservation of angles at this point.

conformal; → mapping.

formal
  دیسه‌ای، دیسه‌ور   
diseyi, desevar

Fr.: formel   

1) According to, or following established or prescribed forms, conventions, etc.
2) Math., logic: Of a proof, in strict logical form with a justification for every step.
3) Math., logic: Of a calculation, correct in form; made with strict justification for every step; of or pertaining to manipulation of symbols without regard to their meaning.
4) → formal language.
5) → formal logic.

M.E. formal, formel, from L. formalis, from → form + → -al.

Diseyi, desevar, from dis, → form, + adj. suffixes -i and -var.

formal language
  زبان ِ دیسه‌ور   
zabân-e disevar

Fr.: langage formel   

A language designed for use in situations in which natural language is unsuitable, as for example in → mathematics, → logic, or → computer  → programming. The symbols and formulas of such languages stand in precisely specified syntactic and semantic relations to one another (Dictionary.com).

formal; → language.

formal logic
  گوییک ِ دیسه‌ای، ~ دیسه‌ور   
guyik-e diseyi, ~ disevar

Fr.: logique formelle   

The traditional or → classical logic in which the → validity or → invalidity of a conclusion is deduced from two or more statements (→ premises). Based on Aristotle's (384-322 BC) theory of → syllogism, systematized in his book "Organon," its focus is not on what is stated (the content) but on the structure (form) of the → argument and the validity of the inference drawn from the premises of the argument; if the premises are true then the logical consequence must also be true. Formal logic is → bivalent, that is it recognizes only two → truth values: → true and → false. The basic principles of formal logic are: 1) → principle of identity, 2) → principle of excluded middle, and 3) → principle of non-contradiction. See also → symbolic logic, → fuzzy logic.

formal; → logic.

formal system
  راژمان ِ دیسه‌ور   
râžmân-e diseyi, ~ disevar

Fr.: système formel   

In logic and mathematics, a system in which statements can be constructed and manipulated with logical rules.

formal; → system.

formaldehyde (H2CO)
  فورمالدهید   
formâldehid

Fr.: formaldehyde   

A colorless gas with a pungent, suffocating odor used as an adhering component of glues in many wood products. Formaldehyde (H2CO) is obtained most commonly by the oxidation of methanol or petroleum gases such as methane, ethane, etc.
In the → interstellar medium, formaldehyde is formed the surface of → dust grains. It is then converted into gas phase by → photodesorption. H2CO was the first → organic molecule discovered in the ISM (Lewis E. Snyder et al. 1969, Phys. Rev. Lett., 22, 679).

From form(ic) acid, from Fr. formique, + → aldehyde.

formalism
  دیسه‌گرایی   
disegerâyi

Fr.: formalisme   

1) Excessive adherence to prescribed forms.
2) Math., Logic: → Formalized expression of a set of elements; the nature of such expression.
3) A philosophical view of mathematics in which mathematics, including the logic used in proofs, can be based on the formal manipulation of symbols irrespective of their meaning.

From → formal + → -ism.

formality
  دیسه‌وری   
disevari

Fr.: formalité   

1) Condition or quality of being formal; accordance with required or traditional rules, procedures, etc.
2) Strict adherence to established rules and procedures (Dictionary.com).

formal; → -ity.

formalization
  دیسه‌ورش   
disevareš

Fr.: formalisation   

1) The act of giving something a form or structure by introducing rules and procedures.
2) The act of formalizing.

formalize; → -tion.

formalize
  دیسه‌ور کردن، دیسه‌وریدن   
disevar kardan, disevaridan

Fr.: formaliser   

1) To state in symbolic form; to give a definite structure to.
2) To give something legal or formal status.

From → formal + → -ize.

Compound verb, from disevar, → formal, + kardan "to do, to make;" Mid.Pers. kardan; O.Pers./Av. kar- "to do, make, build;" Av. kərənaoiti "he makes;" cf. Skt. kr- "to do, to make," krnoti "he makes, he does," karoti "he makes, he does," karma "act, deed;" PIE base kwer- "to do, to make."

Hamiltonian formalism
  دیسه‌گرایی ِ هامیلتون   
disegerâyi-ye Hamilton

Fr.: formalisme de Hamilton   

A reformulation of classical mechanics that predicts the same outcomes as classical mechanics. → Hamiltonian dynamics.

Hamiltonian; → mechanics.

Lagrangian formalism
  دیسه‌گرایی ِ لاگرانژ   
disegerâyi-ye Lâgranži

Fr.: formalisme lagrangien   

A reformulation of classical mechanics that describes the evolution of a physical system using → variational principle The formalism does not require the concept of force, which is replaced by the → Lagrangian function. The formalism makes the description of systems more simpler. Moreover, the passage from classical description to quantum description becomes natural. Same as → Lagrangian dynamics.

Lagrangian; → formalism.

post-Newtonian formalism
  دیسه‌گرایی ِ پسا-نیوتنی   
disegerâyi-ye pasâ-Newtoni

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.

post-; → Newtonian; → formalism.

Press-Schechter formalism
  دیسه‌گرایی ِ پرس-ششتر   
disegerâyi-ye Press-Schechter

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.