Minkowski space [SEP] named after
Minkowski space
In mathematical physics, Minkowski space (or Minkowski spacetime) is a combination of three-dimensional Euclidean space and time into a four-dimensional manifold where the spacetime interval between any two events is independent of the inertial frame of reference in which they are recorded. Although initially developed by mathematician Hermann Minkowski for Maxwell's equations of electromagnetism, the mathematical structure of Minkowski spacetime was shown to be an immediate consequence of the postulates of special relativity.
Minkowski space is closely associated with Einstein's theory of special relativity
D'Alembert operator
In special relativity, electromagnetism and wave theory, the d'Alembert operator (denoted by a box: formula_1), also called the d'Alembertian, wave operator, or box operator is the Laplace operator of Minkowski space. The operator is named after French mathematician and physicist Jean le Rond d'Alembert.
In Minkowski space, in standard coordinates , it has the form (using the box symbol notation)
Here formula_3 is the 3-dimensional Laplacian and is the inverse Minkowski metric with 
Note that the and summation indices range from