Confused by D'alembertian operator in EM

[neu]

I can't understand how the D'Alembertian x 4-vector Vector potential = mu x 4-vector J



Have

$$\nambla^2\A-1\c^2\ frac{ \partial^{2}A}{\partial {t}^{2} } } = \-mu\J$$

 

[neu]

forget it i can't do the font

 

[Thrice]

forget it i can't do the font

Try using https://www.physicsforums.com/showthread.php?t=162979" extension tell me if it helps.