null surface


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null surface

[′nəl ′sər·fəs]
(relativity)
A surface in space-time whose normal vector is everywhere null.
References in periodicals archive ?
One can add to this list a large number of interesting properties; a few among them are as follows: (a) the action functional for Lanczos-Lovelock gravity can be broken into a bulk part and a surface contribution, which is closely related to the Wald entropy associated with the black hole horizon [17]; (b) the field equations in Lanczos-Lovelock gravity can be expressed as a thermodynamic identity on an arbitrary null surface [18-26]; (c) the difference between a suitably defined surface and bulk degrees of freedom in the context of Lanczos-Lovelock gravity can be interpreted as the evolution of the spacetime [27]; (d) the surface and bulk terms in the Lanczos-Lovelock gravity are related by a holographic relation between them [28,29].
Considering a general null surface it turns out that one can interpret [R.sup.a.sub.b][l.sup.b][l.sub.a] as the heat density of the spacetime.
Pei, "Null surfaces of null curves on 3-null cone," Physics Letters.