Is is a typo? The 1985 edition of Schutz:(adsbygoogle = window.adsbygoogle || []).push({}); A First Course in General Relativity, p. 52, equation 2.37, which is supposed to express the idea that "photons have spatial momentum equal to their energy":

[tex]\vec{p} \cdot \vec{p} = -E^2 + E^2 = 0.[/tex]

Shouldn't this be

[tex]\vec{p} \cdot \vec{p} = E^2[/tex]

or

[tex]E^2 - \vec{p} \cdot \vec{p} = 0?[/tex]

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# Printing mistake in A First Course in General Relativity?

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