How to work SortCovDsToBox then !!!

[Ali rezaie]

Hi!

I have many terms including derivatives and boxes and know that \box \xi_a =0.

My terms look like:(in any orders)

\partial \partia \xi (\partial^a\partial_a \partial_c \partial_b \xi_d)+ ......

To omit them I made a rule by:

AutomaticRules[\xi, MakeRule{PD[-a]@PD[a]@\xi[b] , 0}]

Then I am using SortCovDsToBox to commute boxes and derivative to see \box \xi^a =0 through my ansantz.

SortCovDsToBox[\xi][%];

I used it to commute derivatives such that the boxes can act on \xi like the way I learned about SortCovDsToDiv from Loe Stein.But it does not work at all. Not only could not I cancel the terms likes above but also simple forms like \partial \box \xi.

Could you please help me?

many thanks

Ali

PS. I am in Flat space.