- #1

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1)

dx

^{μ}= (dt,dx,dy,dz) I understand thats it's just a four-vector with four componants but, what would

dx

_{μ}be equal to? the same thing?

2)

__FREE INDICES__what does this term mean? free to do what? i.e.

"A

^{μ}A

_{μ}is a scalar because you have no free indices"

Do the upper and lower indices pair?

similarly:

"g

_{μv}g

^{μv}is also a scalar as it has no free indices"

also

"A

^{μ}B

^{v}has two free indices"

Why because they are not paired, what does all this mean?

Thanks for any points in the right direction.