null geodesic

null geodesic

[′nəl ‚jē·ə′des·ik]
(mathematics)
In a Riemannian space, a minimal geodesic curve.
(relativity)
A curve in space-time which has the property that the infinitesimal interval between any two neighboring points on the curve equals zero; it represents a possible path of a light ray. Also known as zero geodesic.
References in periodicals archive ?
The conditions for being class-2 can be best described in terms of properties of the null geodesic congruences spanned by Newman-Penrose vectors (NP) [1,8,11,35,55,71].
r] spanning a null geodesic congruence exist, and has obtained the following two necessary conditions [36]:
4] with Petrov type-II a null geodesic congruence should exist with the three optical scalars equal to zero; (26)
Solving the null geodesic lines equations for this metric, we obtained in [1] that an anisotropy of the velocity of light exists in the z-direction.
All light rays emitted from an event on the symmetry axis reconverge at a later event on this axis, with the null geodesics forming a circular cusp [3].
In our local world, the null geodesics are obviously given by [([ds.
For null geodesics, [epsilon] = 0 and equation (17) yields