Editing Null vector (section)

==Examples==
The [[Minkowski space#Causal structure|light-like]] vectors of [[Minkowski space]] are null vectors.

The four [[linearly independent]] [[biquaternion]]s {{nowrap|1=''l'' = 1 + ''hi''}}, {{nowrap|1=''n'' = 1 + ''hj''}}, {{nowrap|1=''m'' = 1 + ''hk''}}, and {{nowrap|1=''m''<sup>∗</sup> = 1 – ''hk''}} are null vectors and {{nowrap|{ ''l'', ''n'', ''m'', ''m''<sup>∗</sup> }{{void}}}} can serve as a [[basis (linear algebra)|basis]] for the subspace used to represent [[spacetime]]. Null vectors are also used in the [[Newman–Penrose formalism]] approach to spacetime manifolds.<ref>Patrick Dolan (1968) [http://projecteuclid.org/euclid.cmp/1103840725 A Singularity-free solution of the Maxwell-Einstein Equations], [[Communications in Mathematical Physics]] 9(2):161–8, especially 166, link from [[Project Euclid]]</ref>

In the [[Verma module]] of a [[Lie algebra]] there are null vectors.