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 cyclic cosmology (CCC)
keyhânšenâsi-ye carxe-yi-ye hamdis
Fr.: cosmologie cyclique conforme
A cosmological model developped by Roger Penrose and colleagues according which the Universe undergoes repeated cycles of expansion. Each cycle, referred to an aeon, starts from its own "→ big bang" and finally comes to a stage of accelerated expansion which continues indefinitely. There is no stage of contraction (to a "→ big crunch") in this model. Instead, each aeon of the universe, in a sense "forgets" how big it is, both at its big bang and in its very remote future where it becomes physically identical with the big bang of the next aeon, despite there being an infinite scale change involved, on passing from one aeon to the next. This model considers a conformal structure rather than a metric structure. Conformal structure may be viewed as family of metrics that are equivalent to one another via a scale change, which may vary from place to place. Thus, in conformal space-time geometry, there is not a particular metric gab, but an equivalence class of metrics where the metrics ğab and gab are considered to be equivalent if there is a smooth positive scalar field Ω for which ğab = Ω gab (R. Penrose, 2012, The Basic Ideas of Conformal Cyclic Cosmology).
Fr.: géométrie conforme
The study of the set of angle-preserving transformations on a space.
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 x0∈ D if it has the properties of constancy of dilation and preservation of angles at this point.
cosmic star formation peak
cakâd-e keyhâni-ye diseš-e setâregân
Fr.: pic de formation stellaire cosmique
A crucial period in the history of the → Universe, when the bulk of stars in massive galaxies were likely formed. Observations of young stars in distant galaxies at different times in the past have indicated that the → star formation rate peaked at the → redshift of z ~ 2, some 10 billion years ago, before declining by a factor of around ten to its present value (P. Madau & Dickinson, 2014, arXiv:1403.0007).
1) vâdisidan; 2) vâdisândan
Fr.: 1) se déformer; 2) déformer
Fr.: miroir déformable
A very thin mirror whose shape can be changed by the force applied by many small pistons behind the mirror. Such a mirror is used in the → adaptive optics technique to correct the → wavefront affected by the → atmospheric turbulence. See also → tip-tilt mirror.
vâdis, vâdiseš, vâdisâneš
Altering in the size or shape of a body. See also → deformable.
Verbal noun of → deform.
Past participle of → deform.
Fr.: formule de Descartes
A formula that gives the position of an image formed by highly → paraxial rays from a → spherical mirror. It is quite accurately given by: 1/xo + 1/xi = 2/xC, where xo is the distance along the → principal axis from the mirror to the object, xi is the distance from mirror to image, and xC is the distance from the mirror to its center of curvature. Any distance measured on the same side of the mirror as the reflecting surface is positive; on the other side, negative. Thus for a → concave mirror xC is positive; for a → convex mirror, negative.
Fr.: formule dimensionnelle
Symbolic representation of the definition of a physical quantity obtained from its units of measurement. For example, with M = mass, L = length, T = time, area = L2, velocity = LT-1, energy = ML2T-2. → dimensional analysis.
Fr.: déformation élastique
Fr.: formule empirique
1) In physics, a mathematical equation that predicts observed results, but has
no known theoretical basis to explain why it works.
Fr.: formule d'Euler
A formula which expresses an → exponential function
with an → imaginary number
→ exponent in terms of
→ trigonometric functions:
1) dis, disé (#); 2) disidan (#); 3) disândan (#)
Fr.: 1) forme; 2) se former; 3) former
1) (n.) General: The shape and structure of something as distinguished
from its material.
From O.Fr. forme, from L. forma "form, mold, shape, case," origin unknown.
Dis, disé "form, appearance," variants -diz, -diš (tandis
"body form, like a body; effigy;" mâhdis "moon-like;"
šabdiz "night color; a horse of
dark rusty color;" andiš- "to think, contemplate"), from 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").
1) According to, or following established or prescribed forms, conventions, etc.
Diseyi, desevar, from dis, → form, + adj. suffixes -i and -var.
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).
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.
râžmân-e diseyi, ~ disevar
Fr.: système formel
In logic and mathematics, a system in which statements can be constructed and manipulated with logical rules.