An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 28 Search : state
Cassini state
  استات ِ کاسینی   
estât-e Cassini

Fr.: état de Cassini   

A state characterizing a system which obeys → Cassini's laws.

Cassini's law; → state.

  ویژ حالت   

Fr.: état propre   

Quantum mechanics: A dynamical state whose state vector (or wave function) is an → eigenvector of an → operator corresponding to a specified physical quantity.

eigenfunction; → state.

electronic state
  استات ِ الکترونی   
estât-e elektroni

Fr.: état éléctronique   

In molecular quantum mechanics, any of → quantum states corresponding to a particular → electron configuration (i.e. an arrangement of the electron(s) in certain → orbitals). The electron configuration with the lowest energy is called the → ground state. All higher energy states are called → excited states.

electronic; → state.

energy state
  حالت ِ کاروژ   
hâlat-e kâruž

Fr.: état d'énergie   

Same as → energy level.

energy; → state.

equation of state
  هموگش ِ حالت   
hamugeš-e hâlat

Fr.: équation d'état   

In physics and thermodynamics, the equation that describes the relationship between pressure, density, and temperature, e.g. → ideal gas law, → van der Waals equation, → polytropic process, → virial equation of state.

equation; → state.

equation of state parameter
  پارامون ِ هموگش ِ حالت   
pârâmun-e hamugeš-e hâlat

Fr.: paramètre de l'équation d'état   

In cosmology, a → dimensionless parameter introduced by the → equation of state representing the ratio of the pressure to the energy density of a fluid, such as the → dark energy: w = p/ρ. The → deceleration or → acceleration of an → expanding Universe depends on this parameter (→ accelerating Universe). A number of numerical values of this parameter are as follows: for the → cosmological constant: w = -1, for → non-relativistic matter (present-day → baryons): w = 0, and for → relativistic matter (photons, neutrinos): w = +1/3. Together with Ω(dark energy) and Ω(matter), w provides a three-parameter description of the dark energy. The simplest parametrization of the dark energy is w = constant, although w might depend on → redshift.

equation; → state; → parameter.

equilibrium state
  استات ِ ترازمندی، حالت ِ ~   
estât-e tarâzmandi, hâlat-e ~

Fr.: état d'équilibre   

A state in which a → thermodynamic system is in → thermodynamic equilibrium.

equilibrium; → state.

excited state
  حالت ِ بر‌انگیخته   
hâlat-e barangixté (#)

Fr.: état excité   

The condition of a particle or system of particles (especially an atom, nucleus, molecule) after absorbing energy from outside and transiting to a higher → energy level than that of its → ground state. Excited states are transitory as they lose energy through emissions or collisions and return to ground state.

Excited, p.p. of → excite; → state.

ground state
  حالت ِ زمینه   
hâlat-e zaminé (#)

Fr.: état fondamental   

The lowest energy state of an atom, molecule, or ion, when all electrons are in their lowest possible energy levels, i.e. not excited.

ground; → state.

Hartle-Hawking initial state
  استات ِ آغازین ِ هارتل-هاؤکینگ   
estât-e âqâzin-e Hartle-Hawking

Fr.: état initial de Hartle-Hawking   

A proposal regarding the initial state of the → Universe prior to the → Planck era. This → no boundary hypothesis assumes an imaginary time in that epoch. In other words, there was no real time before the → Big Bang, and the Universe did not have a beginning. Moreover, this model treats the Universe like a quantum particle, in an attempt to encompass → quantum mechanics and → general relativity; and attributes a → wave function to the Universe. The wave function has a large value for our own Universe, but small, non-zero values for an infinite number of other possible, parallel Universes.

Hartle, J., Hawking, S., 1983, "Wave function of the Universe," Physical Review D 28; → initial; → state.

Hoyle state
  حالت ِ هویل   
hâlat-e Hoyle

Fr.: état de Hoyle   

An → excited state in the → triple alpha process leading to the production of the most abundant → isotope of → carbon. The existence of this state is of extreme astrophysical importance concerning the → nucleosynthesis of 12C in stellar → cores:
4He + 4He ↔ 8Be,
8Be + 4He ↔ 12C*,
12C*12C + γ.
The process proceeds as follows. First the unstable → ground state of 8Be is formed in the collision of two → alpha particles. Since 8Be exists roughly 7 x 10-17 sec, it must fuse with an alpha particle before breaking up. However, the probability of three bodies merging simultaneously is extremely low. Hoyle showed that the 12C nucleus needs an excited state or resonance at 7.68 MeV to provide for a high reaction probability. The Hoyle state was soon found at 7.65 MeV with the predicted → spin and → parity.

In honor of the British astrophysicist Fred Hoyle (1915-2001), who predicted this state in 1953 (Hoyle et al. 1953, Physical Review 92, 1095); it was discovered by W. A. Fowler in 1957; → state.

macroscopic state
  درشت-استات، درشت-حالت   
dorošt-estât, dorošt-hâlat

Fr.: état macroscopique   

Same as → macrostate.

macroscopic; → state.

  درشت-استات، درشت-حالت   
dorošt-estât, dorošt-hâlat

Fr.: macro-état   

Statistical physics: A state of a physical system that is described in terms of the system's overall or average properties at a macroscopic level (→ temperature, → pressure, → density, → internal energy, etc.). A macrostate will generally consist of many different → microstates. In defining a macrostate we ignore what is going on at the microscopic (atomic/molecular) level. The → probability of a certain macrostate is determined by how many microstates correspond to this macrostate. Therefore, the greater the number of microstates which lead to a particular macrostate, the greater the probability of observing that macrostate. Same as → macroscopic state. See also → entropy, → Boltzmann's entropy formula, → multiplicity.

macro-; → state.

metastable state
  حالت ِ متاپایدار   
hâlat-e matâpâydâr

Fr.: état métastable   

An excited state in an atom, which is at the origin of the spectral lines called → forbidden lines. The time duration of the excited state being relatively long, under laboratory conditions the atom cannot pass directly to the ground state by emitting radiation. In the extremely rarefied interstellar medium, however, such highly improbable transitions do occur.

meta-; → stable; → state.

microscopic state
  ریز-استات، ریز-حالت   
riz-estât, riz-hâlat

Fr.: état microscopique   

Same as → microstate.

microscopic; → state.

  ریز-استات، ریز-حالت   
riz-estât, riz-hâlat

Fr.: micro-état   

Statistical physics: For a system made up of a large number of components, a state of the system which is specified by describing the current dynamical variables of each constituting component. For example, for a gas system composed of a large number of molecules, the microstate is defined by the set of quantities which defines the state of each molecule in the system (position, velocity, vibration, etc.). In practice, it is impossible to know perfectly the microstate of a system. The aim of → statistical physics is to relate the macroscopic (average ) observables (→ pressure, → temperature, → internal energy) to the microstate of the system. Also called → microscopic state. See also → macrostate and → multiplicity.

micro-; → state.

normal state
  حالت ِ هنجارور   
hâlat-e hanjârvar

Fr.: état fondamental   

Of an atom, the same as → ground state.

normal; → state.

oxidation state
  استات ِ اکسایش   
estât-e oksâyeš

Fr.: état d'oxydation   

Same as → oxidation number.

oxidation; → state.

quantum state
  استات ِ کو‌آنتومی   
estât-e kuântomi

Fr.: état quantique   

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

quantum; → state.

singlet state
  حالت ِ تکتایه   
hâlat-e taktâyé

Fr.: état singulet   

In atomic physics, the electronic state of an atom or molecule for which the total → spin angular momentum is zero.

singlet; → state.

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