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Hi
Not sure if this is the best place to post this question but..
Why can we expand [tex](\partial_\mu \phi)^2[/tex] in this way:
[tex](\partial_\mu \phi)^2=(\partial_\mu \phi)(\partial^\mu \phi)[/tex]
I mean [anything]^2 should equal [anything]*[anything] - why have be raised one of the indices above?
thanks.
Not sure if this is the best place to post this question but..
Why can we expand [tex](\partial_\mu \phi)^2[/tex] in this way:
[tex](\partial_\mu \phi)^2=(\partial_\mu \phi)(\partial^\mu \phi)[/tex]
I mean [anything]^2 should equal [anything]*[anything] - why have be raised one of the indices above?
thanks.