- #1
center o bass
- 560
- 2
Hi as I'm reading http://www.maths.tcd.ie/~cblair/notes/432.pdf at page 13 I see that he states that the covariant and contravariant field tensors are different. But how can that be? Aren't they related by
[tex] F_{\mu \nu} = \eta_{\nu \nu'} \eta_{\mu \mu '} F^{\mu ' \nu '} ?[/tex]
and is not the product of the metric tensor eta with it self the identity? I view this as a matrix product
[tex] F = \eta \eta F'[/tex]
and writing out either η or the metric g it seems like their product with each other are the identity such that
[tex] F=\eta \eta F' = I F'.[/tex]
Where is my reasoning wrong?
At page 14 he derived two of the maxwell equations from a lagrangian. But what about the other two? The author just states them. Are not these derivable from a lagrangian?
[tex] F_{\mu \nu} = \eta_{\nu \nu'} \eta_{\mu \mu '} F^{\mu ' \nu '} ?[/tex]
and is not the product of the metric tensor eta with it self the identity? I view this as a matrix product
[tex] F = \eta \eta F'[/tex]
and writing out either η or the metric g it seems like their product with each other are the identity such that
[tex] F=\eta \eta F' = I F'.[/tex]
Where is my reasoning wrong?
At page 14 he derived two of the maxwell equations from a lagrangian. But what about the other two? The author just states them. Are not these derivable from a lagrangian?