Noun
English Wikipedia has an article on:four-vectorWikipedia
four-vector (plural four-vectors)
(mathematics) A vector in four-dimensional vector space, especially one having three spatial dimensions and one temporal dimension.
A photon's wave vector may not be zero and can be represented either as a spatial 3-vector or as a (relativistic) four-vector ; in the latter case it belongs to the light cone (pictured). Source: Internet
Differentiating the above equation by τ produces: : So in special relativity, the acceleration four-vector and the velocity four-vector are orthogonal. Source: Internet
It is the rate of change of the above energy momentum four-vector with respect to proper time. Source: Internet
It turns out they transform exactly like the space-time and energy-momentum four-vectors, : or, in the simpler geometric view, : One says that charge density transforms as the time component of a four-vector. Source: Internet
Relativistic kinematics and invariance The coordinate differentials transform also contravariantly: : so the squared length of the differential of the position four-vector dX μ constructed using : is an invariant. Source: Internet
The energy and momentum, which are separate in Newtonian mechanics, form a four-vector in relativity, and this relates the time component (the energy) to the space components (the momentum) in a non-trivial way. Source: Internet