An Etymological Dictionary of Astronomy and Astrophysics
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1) Of or relating to minute separate → particles.
2) A particulate → substance.

From Mod. L. particulatus, from particula, → particle.

From pârul, → particle, + suffix -é or -mand.

Meteorology: A complex → mixture of → microscopic → particles and → liquid droplets suspended in the → atmosphere, especially pollutants.

→ particulate; → matter.

1a) A division into or distribution in portions or shares.
1b) A separation; something that separates or divides; a part, division, or section.
2a) The act or process of dividing something into parts. The state of being so divided.
2b) Math.: → integer partition; → set partition.
2c) Computers: → disk partition.
3) To divide into parts or portions. To divide or separate by a partition.

M.E., from O.Fr. particion, from L. partition- "division, partition, distribution," from p.p. stem of partire "to part, divide," from PIE root *per- "to grant, allot," related to → part and akin to pake, as below.

Parke, from Kermâni parke "piece, part, fragmant," related to pâr "→ part;" parkidan, infinitive from parke; parkeš, verbal noun of parkidan.

See → integer partition.

→ partition; → function.

The ratio of the → concentration of a → solute in a single definite form in the stationary phase to its concentration in the same form in the other phase at equilibrium.

→ partition; → ratio.

A chemical separation process whereby a solute is distributed between two phases.

→ partition; → -ing.

The act or fact of being partitioned.

→ partition; → -ment.

In particle physics, a constituent of the hadron originally postulated in the theoretical analysis of high-energy scattering of particles off hadrons. In modern usage, the term parton is often used to mean a quark or a gluon.

Coined by the American physicist Richard Feynman (1918-1988), from part, from → particle + → -ion

A fraction of a whole number in units of 1/1000,000. It is usually used to describe chemical concentrations, very small amounts of pollutants in air, water, body fluids, and uncertainty. For example 30 ppm is 3 x 10^-5 or 0.003%.

→ part; → per; → million.

A → participle that indicates a completed action or state.

→ past; → participle.

A → participle that indicates an ongoing action or state in the present.

→ present; → participle.

The representation in → radio wavelengths of an astronomical object that has emission in other parts of the → electromagnetic spectrum.

→ radio; → counterpart.

A particle which has a speed comparable to the velocity of light.

→ relativistic; → particle.

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.

→ resonance; → particle.

A collection of → nonempty subsets of a set A such that every element of A is in exactly one of the subsets. In other words, A is the → disjoint  → union of these subsets.

→ partition; → set.

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).

→ sink; → particle.

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.

The theory developed since the 1970s, which is based on the theories and discoveries since the 1930s, and aims at explaining the fundamental structure of matter. According to the standard model, everything in the universe is made from a few basic building blocks called fundamental particles, governed by four fundamental forces. The particles occur in two basic types, called quarks and leptons. Three of the four fundamental forces (except gravity) and their carrier particles are included in the Standard Model. The Standard Model has successfully explained almost all experimental results and precisely predicted a wide variety of phenomena. Over time and through many experiments, the Standard Model has become established as a well-tested physics theory.

→ standard; → model; → particle; → physics.

An elementary particle created in high-energy particle collisions having a short life and a strangeness quantum number of 1. For example, sigma and xi baryons are strange particles. A strange particle is produced when a strange quark is created in a high-energy collision. → strangeness.

→ strange; the concept of "strange" arose from the observation that these particles decay rapidly, in contrast to others that do not. → particle.

Any particle that is small compared to the size of the atom, e.g. an electron, proton, neutron, neutrino, quark, meson, all of which are either bosons or fermions.

→ subatomic; → particle.