I am trying to assign values for a tensor but receive![ that is neither a list of replacement rules nor a valid dispatch table, \ and so cannot be used for replacing ][1]:
The code (also attach an nb):
A = CTensor[{-qE CE e r[]/(c (r[]^2 + a^2 Cos[\[Theta][]]^2)), 0,
0, qE CE e a r[] Sin[\[Theta][]]^2/(c (r[]^2 +
a^2 Cos[\[Theta][]]^2))}, {-BL}];
(*Define field strength components*)
(*fieldStrengthRule=MakeRule[F[-\[Mu],-\[Nu]],CovD[-\[Mu]][A[-\[Nu]]]-\
CovD[-\[Nu]][A[-\[Mu]]]];*)
F = CTensor[Array[0 &, {4, 4}], {-BL, -BL}];
F[-\[Mu], -\[Nu]] /.
Evaluate[
MakeRule[F[-\[Mu], -\[Nu]],
CovD[-\[Mu]][A[-\[Nu]]] - CovD[-\[Nu]][A[-\[Mu]]]]] //
ContractBasis // Simplify // MatrixForm
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