Fr.: particule alpha
A positively charged particle emitted from the nuclei of certain atoms during radioactive disintegration. The alpha particle has an atomic weight of 4 and a positive charge equal in magnitude to 2 electronic charges; hence it is essentially a helium nucleus.
Any → elementary particle with a → charge of opposite sign to the same particle in normal matter.
Fr.: physique des astroparicules
The area of science which deals with → elementary particle and → high-energy phenomena in → astrophysics and → cosmology.
beam of particles
Fr.: faisceau de particules
A narrow unidirectional flow of particles
zarre-ye betâ (#)
Fr.: particule bêta
An → electron or a → positron emitted from an unstable nucleus during a → radioactive process known as → beta decay.
The term "beta particle" relates to the early history of the → radioactivity studies when the nature of the emergent particles was not elucidated; → particle.
zarre-ye bârdâr (#)
Fr.: particule chargée
Any particle containing either a → positive or → negative → electric charge.
zarre-ye bonyâdin (#)
Fr.: particule élémentaire
A particle which cannot be divided into other constituents. More specifically, a particle whose field appears in the fundamental field equations of the unified field theory of elementary particles, in particular in the Lagrangian. For example, the → electron, the → photon, and the → quark are elementary particles, whereas the proton and neutron are not. The elementary nature of a particle can be revised depending on new observations or theories. Also called → fundamental particle.
Elementary, M.E. elementare, from M.F. élémentaire, from L. elementarius, from → element + adj. suffix -arius; → particle.
Bonyâdin, from bonyâd "basis, foundation," variant of bonlâd, from bon "basis; root; foundation; bottom" → element + lâd "root; foundation; reason, cause; wall" + adj. suffix -in.
energetic solar particles
zarrehâ-ye xoršidi-ye kâružmand
Fr.: particules solaires énergétiques
Electrons and atomic nuclei ejected by solar flares, travelling with velocities amounting to a fraction of the velocity of light, and energies mostly in the range 1-100 million → electronvolts (eV), but occasionally as high as 15 billion eVs. Also known as solar → cosmic rays.
Energetic, from Gk. energetikos, from energe-, → energy, + -tikos a suffix, equivalent in meaning to → -ic, occurring in adjectives; → solar; → particle.
Zarrehâ plural of zarré, → particle; xoršidi, → solar; kâružmand from kâruž, → energy, + -mand possession suffix.
Fr.: particule d'échange
In quantum field theory, a particle that transfers momentum and energy between interacting objects, and is said to mediate the interaction. All four of the fundamental forces involve the exchange of one or more particles. For example, photon is the exchange particle of the electromagnetic force.
zarre-ye bonyâdin (#)
Fr.: particule élémentaire
Same as → elementary particle.
→ fundamental; → particle.
Fr.: particule lagrangienne
Fluid mechanics: In the → Lagrangian method, a particle that moves as though it is an element of fluid. The particle concept is an approach to solving complicated fluid dynamics problems by tracking a large number of particles representing the fluid. The particle may be thought of as the location of the center of mass of the fluid element with one or more property values.
→ Lagrangian; → particle.
A solid particle of → nanoscale size; e.g. a → nanodust grain.
1) , 2) zarré (#), 1), 2), 3) pârul
1) A unit of → matter smaller than the
→ atom or its main components.
The term particle also includes any (currently hypothetical) new particles
that might be discovered, such as the supersymmetric partners of the
→ quarks and → leptons
and → bosons.
From L. particula "little bit or part," diminutive of pars (genitive partis), from PIE base *per- "to assign, allot;" cf. Mid.Pers. pârag "gift, offering, bribe;" Mod.Pers. pâreh "gift" (→ partial); Gk. porein "to provide, give, grant," peprotai "it has been granted;" Skt. purtá- "gift, pay, reward."
Zarré, from Ar. dharrat "particle." Pârul, from pâr, → part, + -ul, → -ule.
Fr.: horizon des particules
For an observer at a given epoch t0, the boundary between the observable and the unobservable regions of the → Universe. Therefore, the distance to the particle horizon at t0 defines the size of the → observable Universe. Same as → cosmic horizon.
Fr.: nature de particule
A general term to describe → light involving the following phenomena: → reflection, → refraction, and → photoelectric effect. Compare → wave nature.
fizik-e zarreyi (#)
Fr.: physique des particules
The branch of physics that deals with the smallest known structures of matter and energy in order to understand the fundamental particles and forces of nature.
Fr.: particule relativiste
A particle which has a speed comparable to the velocity of light.
→ relativistic; → particle.
Fr.: particule de résonance
A hadronic particle which exists for only a very brief time (10-23 seconds) before decaying into hadrons; also called resonance. The existence of a resonance cannot be observed directly; it can only be inferred from studying the longer-lived products of its decay.
Fr.: particule puits
In hydrodynamics codes, a way of treating a collapsing or accreting region, such as a star, as a simple → point mass. Indeed, in many situations, the scale of interest is much larger than the scale of the → accreting object itself and it would be impossible to perform the calculation otherwise. → Sinks are generally modeled as → Lagrangian particles (see, e.g., Bates et al. 1995, MNRAS 277, 362; Krumholz et al. 2004, ApJ 611, 399; Federrath et al. 2010, ApJ 713, 269).
Smoothed Particle Hydrodynamics (SPH)
hidrotavânik-e zarrehâ-ye hamvâridé
Fr.: hydrodynamique des particules lissées
A numerical method for modeling → compressible hydrodynamic flows, which uses particles to simulate a continuous fluid flow. Because the system of hydrodynamical basic equations can be analytically solved only for few exceptional cases, the SPH method provides a numerical algorithm to solve systems of coupled → partial differential equations for continuous field quantities. The main advantage of the method is that it does not require a computational grid to calculate spatial → derivatives and that it is a Lagrangian method, which automatically focuses attention on fluid elements. The equations of motion and continuity are expressed in terms of ordinary differential equations where the body forces become classical forces between particles. This method was first independently developed by Lucy (1977, AJ 82, 1013) and Gingold & Monaghan (1977, MNRAS 181, 375).
Smoothed Particle Hydrodynamics, first used by Gingold & Monaghan (1977); → smooth; → particle; → hydrodynamics.