
C
H
(G)
λ(g, g
0
) C
H
(G
n
)
λ(g, g
0
) = λ(h, h
0
) (g, g
0
) (h, h
0
)
C
H
(G
n
)
λ(g, g
0
)
C
H
(G
n
) λ(g, g
0
) =
λ(h, h
0
) g
0
g
−1
h
0
h
−1
G λ
C
H
(G
n
)
G
λ G
G
G mod 4
X = {0, . . . , r −1}
mod r
l(a, b) a, b ∈ X
b − a ∈ X a − b ∈ X l(a, b) = min(b − a mo d r, a − b mod r)
r = 5 l(0, 1) = 1 l(4, 1) = 2
l(a, b)
λ
q−
λ(g, g
0
), g, g
0
∈
G, G
λ(g, g
0
) = λ(gh, g
0
h) h ∈ G.
C
H
(G) C
H
(G)
λ(g, g
0
) =
b
λ(hg, hg
0
)
λ N
g,g
0
(a, b)
h ∈ G λ(g, h) = a, λ(h, g
0
) = b
c = λ(g, g
0
) N
g,g
0
(a, b) = N
c
(a, b)