Four-gradient

The four-gradient is the Four-vector generalization of the Gradient :

:

\partial_\alpha \ \stackrel{\mathrm{def}}{=}\  \left(rac{1}{c} rac{\partial}{\partial t}, 
abla 
ight)

and is sometimes also represented as ''D''.

The square of ''D'' is the four- Laplacian , which is called the D'Alembert Operator :

:

D\cdot D = \partial_\alpha \partial^\alpha = - rac{1}{c^2}rac{\partial^2}{\partial t^2} + 
abla^2

.

As it is the Dot Product of two four-vectors, the d'Alembertian is a Lorentz Invariant scalar.

It is also written

\Box

	CATEGORIES ABOUT FOUR-GRADIENT

	relativity

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