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If we have this term $$\frac{1}{2}N_{IJ}F_{\mu\nu}^I\tilde{F}^{J\mu\nu} $$ and I want to derive w.r.t ##F^{\rho\sigma I}##

where

- ##N_{IJ}## is a symmetric complex matrix

- ##\tilde{F}^{\mu\nu}=\frac{1}{2}\epsilon^{\mu\nu\rho\sigma}F_{\rho\sigma}##

- How to derive w.r.t ##F^{\rho\sigma I}##? (I have no ##\rho\sigma## in the term above--- I know this how it goes but I have no idea how).

That is to say, had the derivation were w.r.t ##F^{\mu\nu}## and I had instead of ##\frac{1}{2}N_{IJ}F_{\mu\nu}^I\tilde{F}^{J\mu\nu}## a ##1/2F^{\mu\nu}F_{\mu\nu}##, the derivation would give me an ##F_{\mu\nu}##, but in this simple example I presented now, there is no F with indices ##{\rho\sigma I}## instead of ##{\mu\nu}##.