# Can somebody explain why the action in the picture is true?

I can provide the resource for where this is from. Can somebody explain how to get this expression?

• "I can provide the resource for where this is from" Please do. It's of no use to state that you can provide the source and then not provide it. – ACuriousMind Sep 1 '18 at 17:31

1. OP's action (1.2) can be viewed as the "point-particle Polyakov action" in the $e=1/m$ gauge, cf. this Phys.SE. (Here $g^{\text{OP}}_{\mu\nu}=m^2g_{\mu\nu}$.)