- #1
latentcorpse
- 1,444
- 0
If [itex]j^\mu = ( j^0 , \vec{j} )[/itex], why does
[itex]\partial_\mu j^\mu = \partial_0 j^0 + \vec{\nabla} \cdot \vec{j}[/itex]
surely when you take a dot product of four vectors you get a subtraction as in
[itex]a^\mu b_\mu = a^0 b_0 - \vec{a} \cdot \vec{b}[/itex]
Maybe I'm forgetting something
[itex]\partial_\mu j^\mu = \partial_0 j^0 + \vec{\nabla} \cdot \vec{j}[/itex]
surely when you take a dot product of four vectors you get a subtraction as in
[itex]a^\mu b_\mu = a^0 b_0 - \vec{a} \cdot \vec{b}[/itex]
Maybe I'm forgetting something