E B χ
A+1
c
∂φ
∂t = 0.
Aφ
=1
c2
∂2
∂t2− ∇2,
φ=ρ, A=j.
O(1,3)
R4x0=ct
x= (x1, x2, x3) = (x, y, z)
gµν =gµν = (−1,1,1,1).
g
xµ=gµν xν, pµ=gµν pν.
∂µ=∂/∂xµ
(∂0, . . . , ∂3) = (c−1∂t,∇x),(∂0, . . . , ∂3)=(c−1∂t,−∇x),
∂2=∂2
0−∂2
1−∂2
2−∂2
3=c−2∂2
t− ∇2
x.
A F
j
Aµ= (φ, A), i.e. Aµ= (φ, −A),
Fµν =∂µAν−∂νAµ, i.e. F µν =∂µAν−∂νAµ,
jµ= (ρ, j)i.e. jµ= (ρ, −j).
∂µAµ= 0, ∂µjµ= 0,
∂κFµν +∂µFνκ +∂νFκµ = 0,
∂2Aµ=jµ.