snoopies622

Here and there I come across the following formula for the Lagrangian density of a real scalar field, but not a deriviation.

[tex]
\mathcal{L} = \frac {1}{2} [ \dot \phi ^2 - ( \nabla \phi ) ^2 - (m \phi )^2 ]

[/tex]

Could someone show me where this comes from? The m squared term in particular is a mystery.