Minkowski Metric

$${\eta }^{\mu \nu }=\left[\begin{array}{cccc}-1& 0& 0& 0\\ 0& 1& 0& 0\\ 0& 0& 1& 0\\ 0& 0& 0& 1\end{array}\right]$$

• Used to set the d’Alembert operator into hyperbolic spacetime geometry
• Alternatively negative as + - - - instead of - + + +