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

The area of calculus dealing with differentiation and integration of vector-valued functions; a sub-area of tensor calculus.

→ calculus; → vector.

Afmârik, → calculus; bordâr, → vector.

Math.: A nonzero vector v whose direction is not changed by a given linear transformation T; that is, T(v) = λ v for some scalar λ.

→ eigenfunction; → vector.

A → vector field on a → Riemannian manifold (or → pseudo-Riemannian manifold) that preserves the → metric. In other words, the → derivative of the metric with respect to this vector field is null.

Named after the German mathematician Wilhelm Killing (1847-1923); → vector.

A vector field A defined so that the → magnetic field  B is given by its → curl: B = ∇ x A.

→ magnetic; → vector; → potential.

Two non-zero vectors which are perpendicular, i.e. their → scalar product is zero.

→ orthogonal; → vector.

Two non-zero vectors that are → orthogonal and have magnitude 1.

→ orthogonal; → vector.

The amount of electromagnetic energy flowing through unit area, perpendicular to the direction of energy propagation, per unit time, given by (c/2 π)[E x H]. → Poynting's theorem.

→ Poynting's theorem; → vector.

Math.: In a system of polar or spherical coordinates, a line joining a point to the origin.
Astro.: A line drawn from a central body to a satellite object in any position in its orbit.

→ radius; → vector.

A vector indicating the direction in which interstellar reddening moves the position of a star in a multi-dimensional space of color indices.

→ reddening; → vector.

A → relative tensor of → order  → one.

→ relative; → vector.

A theory put forward to provide a basis for a relativistic generalization of the → MOdified Newtonian Dynamics (MOND) paradigm. TeVeS is based on three dynamical fields: a tensor field, a vector field, and a scalar field. In contrast to general relativity, it has two metrics, an Einstein metric and a physical metric. TeVeS has attracted considerable attention, since it can explain many galactic and cosmological observations without the need for → dark matter. Proposed by J. D. Bekenstein, 2004, "Relativistic gravitation theory for the modified Newtonian dynamics paradigm", Phys. Rev. D, 70, 083509, arXiv:astro-ph/0403694.

→ tensor; → vector; → scalar; → theory.

A vector of length 1, also called a direction vector.

→ unit; → vector.

Any physical quantity which requires a direction to be stated in order to define it completely, for example velocity. Compare with → scalar.

From L. vector "one who carries or conveys, carrier," from p.p. stem of vehere "carry, convey;" cognate with Pers. vâz (in parvâz "flight"); Av. vaz- "to draw, guide; bring; possess; fly; float," vazaiti "guides, leads" (cf. Skt. vah- "to carry, drive, convey," vahati "carries," pravaha- "bearing along, carrying," pravāha- "running water, stream, river;" O.E. wegan "to carry;" O.N. vegr; O.H.G. weg "way," wegan "to move," wagan "cart;" M.Du. wagen "wagon;" PIE base *wegh- "to drive").

Bordâr "carrier," agent noun from bordan "to carry, transport" (Mid.Pers. burdan; O.Pers./Av. bar- "to bear, carry," barəθre "to bear (infinitive);" Skt. bharati "he carries;" Gk. pherein "to carry;" L. ferre "to carry;" PIE base *bher- "to carry").

The study of → vectors and → vector spaces.

→ vector; → analysis.

Of a rotating body, a vector of magnitude ω (→ angular velocity) pointing in the direction of advance of a right-hand screw which is turned in the direction of rotation.

→ vector; → angular; → velocity.

In nuclear physics, a → boson with the spin quantum number equal to 1.

→ vector; → boson.

The study of vector functions between vector spaces by means of → differential and integral calculus.

→ vector; → calculus.

A → tensor density of → order 1.

→ vector; → density.

A vector each of whose → components is a → scalar field. For example, the → gradient of the scalar field F, expressed by: ∇F = (∂F/∂x)i + (∂F/∂y)j + (∂F/∂z)k.

→ vector; → field.

A function whose value at each point is n-dimensional, as compared to a scalar function, whose value is one-dimensional.

→ vector; → function.