LeftRightPartialD[mu] denotes , acting to the left and right. ExplitPartialD[LeftRightPartialD[]] gives 1/2 (RightPartialD[] - LeftPartialD[]).
See also: ExplicitPartialD, ExpandPartialD, PartialD, LeftPartialD, LeftRightPartialD2, RightPartialD.
The FeynCalc Book | LeftPartialD | LeftRightPartialD2 |