α=xdy −ydx
x2+y2
R2\ {0}
R4x, y, z, t x, y, z
t E B
R3
(E) = −∂B
∂t (B)=0
(B) = ∂E
∂t (E)=0.
∗: Ω2(R4)→Ω2(R4)
∗(dx ∧dt) = dy ∧dz, ∗(dy ∧dt) = dz ∧dx, ∗(dz ∧dt) = dx ∧dy,
∗(dy ∧dz) = −dx ∧dt, ∗(dz ∧dx) = −dy ∧dt, ∗(dx ∧dy) = −dz ∧dt,
2F∈Ω2(R4)
F=Exdx ∧dt +Eydy ∧dt +Ezdz ∧dt +Bxdy ∧dz +Bydz ∧dx +Bzdx ∧dy.
dF = 0, d ? F = 0
Rn(x1, . . . , xn−1, xn=t)
Rnω∈Ωk(Rn)ω ω =α+dt ∧β
α=
n−1
X
i1,...,ik=1
ai1,...,ik(x, t)dxi1∧. . . ∧dxik=: aI(x, t)dxI∈Ωk(Rn)
β=
n−1
X
j1,...,jk−1
bj1,...,jk−1(x, t)dxj1∧. . . ∧dxjk−1=: bJ(x, t)dxJ∈Ωk−1(Rn),
I={i1, . . . , ik}⊂{1, . . . , n −1}J={j1, . . . , jk−1}⊂{1, . . . , n −1}α β
dt
dω =d0α+d00α−dt ∧d0β d0α d0β dα dβ d00β
dβ
ω dω = 0
d0β=∂aI
∂t (x, t)dxI.
Rnω∈Ωk(Rn)k ω ∈Ωk(Rn)