Friday, 23 August 2019

special relativity - Can the overall sign of the Minkowski metric be changed?


If we take the Minkowski metric, ημν=(1,1,1,1), instead of the usual (1,1,1,1), does this change the form of the Lorentz Transform? I think the standard Lorentz Transform looks like: (γγβ00γβγ0000100001)



Answer



An interesting question indeed :-) Yes, you can flip the overall sign of the Minkowski metric, and in fact a lot of physicists do this! The sign choice diag(1,1,1,1) is conventional in fundamental quantum field theory and in quantum gravity, if I remember correctly, whereas diag(1,1,1,1) is conventional in particle physics.


This doesn't affect the Lorentz transform, though. If you apply the Lorentz transform to a metric tensor, it computes as gαβ=ΛμαΛνβgμν, and so you will automatically come out with the same sign convention that you put in.


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