The stretching and squishing factors for the diagonals are the same as the Doppler shift. We notate this factor as D (which can stand for either “Doppler” or “diagonal”).
A four-vector is an object with four components, which transform in a specific way under Lorentz transformations. Specifically, a four-vector is an element of a four-dimensional vector space considere...A four-vector is an object with four components, which transform in a specific way under Lorentz transformations. Specifically, a four-vector is an element of a four-dimensional vector space considered as a representation space of the standard representation of the Lorentz group. The transformations that preserve this magnitude are the Lorentz transformations, which include spatial rotations and boosts.
