Could SR not be built from only one postulate?

[stevendaryl]

Charge density is the time-like component of the current 4-vector and charge is a Lorentz scalar. Charge is defined as the integral of the charge density over a space-like hypersurface. The proof that charge is a Lorentz scalar is actually quite simple, given the 4-divergence of the current 4-vector. It's basically just an application of Stokes' theorem.

Yes, you're right. I can't find my copy of Jackson, so I'm not sure what the alternative theory is that reduces to Coulomb's law in the nonrelativistic limit.

 

[bhobba]

In this regard the following is interesting if you can get a hold of it:
http://adsabs.harvard.edu/abs/1994AmJPh..62..914H

Also see:
http://arxiv.org/pdf/0812.4785v1.pdf

Thanks
Bill

 

[Meir Achuz]

Charge density is the time-like component of the current 4-vector and charge is a Lorentz scalar. Charge is defined as the integral of the charge density over a space-like hypersurface. The proof that charge is a Lorentz scalar is actually quite simple, given the 4-divergence of the current 4-vector. It's basically just an application of Stokes' theorem.

The 4D divergence theorem