LeftRightPartialD2[mu] denotes \overleftrightarrow{\partial }_{\mu }, acting
to the left and right.
ExplicitPartialD[LeftRightPartialD2[mu]] gives
(RightPartialD[mu] + LeftPartialD[mu]).
Overview, ExplicitPartialD, ExpandPartialD, FCPartialD, LeftPartialD, RightPartialD.
LeftRightPartialD2[\[Mu]]
ExplicitPartialD[%]\overleftrightarrow{\partial }_{\mu }
\overleftarrow{\partial }_{\mu }+\vec{\partial }_{\mu }
LeftRightPartialD2[\[Mu]] . QuantumField[A, LorentzIndex[\[Nu]]]
ExpandPartialD[%]\overleftrightarrow{\partial }_{\mu }.A_{\nu }
\left.(\partial _{\mu }A_{\nu }\right)+\overleftarrow{\partial }_{\mu }.A_{\nu }
QuantumField[A, LorentzIndex[\[Mu]]] . LeftRightPartialD2[\[Nu]] . QuantumField[A, LorentzIndex[\[Rho]]]
ExpandPartialD[%]A_{\mu }.\overleftrightarrow{\partial }_{\nu }.A_{\rho }
A_{\mu }.\left(\left.(\partial _{\nu }A_{\rho }\right)\right)+\left(\left.(\partial _{\nu }A_{\mu }\right)\right).A_{\rho }