I am confused by something basic stated in this https://physics.stackexchange.com/a/429947/42982 by @ACuriousMind and some fact I knew of. Here dA is covariant derivative.
dAA=F --- @ACuriousMind says "The field strength is the covariant derivative of the gauge field."
The Bianchi identity is dAF=0.
- In the 1st case, we need to define
dA=d+A∧
So dAA=(d+A∧)A=dA+A∧A
- In the 2nd case, we need to define
dA=d(..)+[A,..]
So we get a correct Bianchi identity which easily can be checked to be true dAF=dF+[A,F]=d(dA+AA)+[A,dA+AA]=0
However, eq (1) and (2) look different.
e.g. if we use eq(2) for "The field strength is the covariant derivative of the gauge field.", we get a wrong result
dAA=dA+[A,A]=dA≠F!!!!
e.g. if we use eq(1) for "Bianchi identity", we get the wrong result we get dAF=dF+A∧F≠0
my puzzle: How to resolve def (1) and (2)?
Could it be that for the p-form dAω=dω+…,
where … depends on the p of the p-form? How precisely?
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