φ
H1(GK, Ks×) := {f:GK→Ks×/∀(s0, s1)∈G2
K, f(s0s1) = f(s0)s0(f(s1))}
{GK→Ks×, s 7→ s(µ)µ−1/µ ∈Ks×}
Pn(Ks)GK=Pn(K)
H1(G, M) = {f:G→M/∀(s0, s1)∈G2, f (s0s1) = f(s0) + s0·f(s1)}
{G→M, s 7→ s·m−m/m ∈M}
G M G
s·(m1+m2) = s·m1+s·m2s∈G m1, m2∈M
G
G M G s ·(m1+
m2) = s·m1+s·m2s∈G m1, m2∈M
M G
F(G0, M)d0
//F(G1, M)d1
//F(G2, M)d2
//...
G0={1} F(Gi, M)GiM
dif(s0, ..., si) = s0f(s1, ..., si) +
i
X
k=1
(−1)kf(s0, ..., sk−1sk, ..., si)+(−1)i+1f(s0, ..., si−1)
f∈ F(Gi, M)di+1 ◦di= 0
(di)⊆(di+1)r M Hr(G, M) =
(dr)/(dr−1)
G
Hr(G, −)r
M→MGG
G
G= (K/k)G(L/k)
L k K
G
G G M
G×M→M, (g, m)7→ gm
M G r Hr(G, M)M
F(Gi, M)
GiM r
M7→ MGG