In special relativity, electromagnetism and wave theory, the d'Alembert operator, also called d'Alembertian, is the Laplace operator of Minkowski space. Thus, in the standard coordinate basis, where | g | = 1, it has the form Special relativity (SR) or the special theory of relativity is the physical theory published in 1905 by Albert Einstein. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... This article is about waves in the most general sense; a separate article focuses on ocean waves. ... In vector calculus, the Laplace operator or Laplacian is a differential operator equal to the sum of all the unmixed second partial derivatives of a dependent variable. ... In physics and mathematics, Minkowski space (or Minkowski spacetime) is the mathematical setting in which Einsteins theory of special relativity is most conveniently formulated. ...

Clearly the sign of these expressions depend on the sign convention used for the Minkowski metric. In some physics textbooks and articles, certain quantities are defined with the opposite sign from that which is used in other publications. ...

Lorentz transformations leave the metric invariant, thus the above coordinate expressions remain valid in every inertial frame. The Lorentz transformation (LT), named after its discoverer, the Dutch physicist and mathematician Hendrik Antoon Lorentz (1853-1928), forms the basis for the special theory of relativity, which has been introduced to remove contradictions between the theories of electromagnetism and classical mechanics. ...