An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A random variation of signal due to fluctuations in the average rate of incidence of quanta on a detector. Quantum noise is described by the → Poisson distribution. Same as → photon noise and → shot effect.

→ quantum; → noise.

A number used in quantum mechanics, specifying the state of an electron bound in an atomic system. The quantum numbers are integers or half integers and specify the number of units of energy, momentum, spin, etc. possessed by an electron.

→ quantum; → number.

Since → Planck's constant has the dimension of → energy × → time, its sometimes called the quantum of → action.

→ quantum; → action.

A phase transitions that occurs at zero temperature as a function of a non-thermal parameter like → pressure, → magnetic field, or → chemical composition. In contrast to ordinary → phase transitions, which are associated with passage through a critical temperature, quantum phase transitions are associated with → quantum fluctuations, a consequence of → Heisenberg's uncertainty principle. For example, see → Bose-Einstein condensation.

→ quantum; → phase; → transition.

In → quantum mechanics, the state of a system as described by a set of → quantum numbers and represented by an → eigenfunction.

→ quantum; → state.

The theoretical basis of modern physics which describes the behavior and interactions of elementary particles or energy states based on the assumptions that energy is subdivided into discrete amounts and that matter possesses wave properties. → quantum mechanics; → quantum field theory.

→ quantum; → theory.

A property in → quantum mechanics whereby in a quantum system the sum of all probabilities of all possible outcomes must be 1. Quantum unitarity makes the modulous of a → quantum state invariant with time.

→ quantum. → unitary.

A generalization of the classical concept of → random walk using quantum mechanical laws such as the → superposition principle and → interference of quantum amplitudes. In the classical version the particle moves in the position space with a certain probability. In contrast, in the quantum counterpart the particle moves by exploring multiple possible paths simultaneously with the amplitudes corresponding to the influence of different paths. The concept of quantum walk is studied in two standard forms: → continuous-time quantum walk and → discrete-time quantum walk. Quantum walk was first introduced by Aharonov et al. (1993, Phys. Rev. A, 48, 1687).

→ continuous; → walk.

In photochemistry, the number of defined events which occur per photon absorbed by the system.

→ quantum; → theory.

A linear → Hermitian operator associated with a physical quantity.

→ quantum; → mechanics; → operator.

A faint object (magnitude 18.5), probably a dwarf planet, orbiting the Sun beyond Neptune in the Kuiper belt. Discovered in 2002, Quaoar is estimated to have a diameter of 1260 km and an orbital period of 287 years.

Quaoar the name of a creation deity of the Native American Tongva, located in the Los Angeles area, where the discovery was made.

Any of the hypothetical particles with spin 1/2, baryon number 1/3, and electric charge 1/3 or -2/3 that, together with their antiparticles, are believed to constitute all the elementary particles classed as baryons and mesons. Quarks are distinguished by their flavors, designated as up (u), down (d), strange (s), charm (c), bottom or beauty (b), and top or truth (t), and their colors, red, green, and blue. The key evidence for the existence of quarks came from a series of inelastic electron-nucleon scattering experiments (→ inelastic scattering) conducted between 1967 and 1973 at the Stanford Linear Accelerator Center. Other theoretical and experimental advances have confirmed this discovery, leading to the → standard model of particle physics.

Quark, coined in 1963 by the American physicist Murray Gell-Mann (1929-), who took it from a nonsense word in James Joyce's novel Finnegans Wake (1939): Three quarks for Muster Mark! // Sure he has not got much of a bark // And sure any he has it's all beside the mark.

The phenomenon wherein the → quarks are permanently bound together and can never be removed from the → hadrons they compose.

→ quark; → confinement.

A hypothetical star so dense that it is composed of degenerate quarks, a matter denser than that of a neutron star.

→ quark; → star.

A phase transition, predicted by cosmological models, to have occurred at approximately 10^-5 seconds after the Big Bang to convert a plasma of free quarks and gluons into hadron.

→ quark; → hadron; → phase; → transition.

A fourth of the Moon's period or monthly revolution around Earth. → first quarter; → last quarter.

from O.Fr. quartier, from L. quartarius "fourth part," from quartus "fourth," related to quattuor "four," cognate with Pers. câr, cahâr, as below.

Cârak "quarter," literally "fourth, a fourth part of one," from câr, contraction of cahâr, → four, + -ak, contraction of yak, yek "one." Yek "one, alone," from Mid.Pers. êwak (Proto-Iranian *aiua-ka-); O.Pers. aiva- "one, alone;" Av. aēuua- "one, alone;" cf. Skt. éka- "one, alone, single;" Gk. oios "alone, lonely;" L. unus "one;" E. one.

A plate of doubly refracting material cut parallel to the optic axis of the crystal and of such a thickness that a phase difference of 90° is introduced between the ordinary and extraordinary rays for light of a particular wavelength. → half-wave plate.

→ quarter; → wave; → plate.

An equation containing unknowns of the fourth power; the general form: ax⁴ + bx³ + cx² + dx + e = 0.

From L. quart(us) "fourth" (→ quarter) + → -ic; → equation.

hamugeš, → equation; câromân, from cârom "fourth," from câr, cahâr "four" + -om "-th" + -ik, → -ic.

In statistics, any of the four groups of a frequency distribution each containing 25% of the total number of individual observations.

From M.L. quartilis, from quart(us) "fouth" + -ilis "-ile" a suffix of adjectives expressing capability, susceptibility, liability, aptitude.

Cârakvâr, from cârak, → quarter, + -vâr suffix of similarity, size, aptitude.

One of the most abundant → minerals in the Earth's → crust. Quartz is made up of silicon dioxide (SiO₂), or → silica. It has marked → piezoelectric properties and → dielectric strength.

From Ger. Quarz "rock crystal," from M.H.G. twarc.