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. n - f: n , (x 1, x 2, , xn) Î n x Î . : x = f(x 1, x 2, , xn). . , , F = (f 1, f 2, ).
F ( ) A(X, F). - .
, . ( ) ( ) f:2 . , - (x1, x2) f(x 1, x 2 ) . : T, *, ◦, + f(x 1, x 2 ) = z x T y = z. , .
, - x, y, z Î (x T y) T z = x T (y T z).
, - x, y Î x T y = y T x.
T1 T2, - x, y, z Î x T 1(y T 2 z) =(x T 1 y) T2 (x T 1 z). T 1 T2, - x, y, z Î (y T 2 z) T 1 x =(x T 1 y) T 2(x T 1 z). T1 T 2, .
() , - x Î e T x = x. () , - x Î x T e = x. () , , - x Î x T e = e T x = x. , : , e 1¹ e 2, e 1 = e 1 T e 2= e 2 .
x -1 x Î , x‑ 1 T x = e. x -1 x Î , x T x- 1 = e. x -1 x Î , , x- 1 T x = x T x -1 = e.
, , , . , . .
a1 | a2 | an | ||
a1 | a1Ta1 | a1Ta2 | a1Tan | |
a2 | a2Ta1 | a2Ta2 | a2Tan | |
an | anTa1 | anTa2 | anTan |
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ϳ
. ϳ .
().
1) Ω - (Ω) - ( Ω ). (Ω) , . (Ω) . .
2) n(R) n x n ;
3) Ω - (Ω) - . (Ω) . (Ω) . Ω.
4) , n > 1, .
ϳ , , .
, G, ( ) :
(G1) : (x y) z = x (y z) x, y, z Î G;
(G2) G () : e x = x e = x x Î G;
(G3) x Î G x -1, x -1 x = x x -1= e.
, , - x, y Î G x y = y x, () .
, . . G , | G | .
(G1) - (G3) .
1. : x y = x z, y = z ( );
y x = z x, y = z ( );
2. ;
3. a, b Î G a x = b y a = b .
:
1) Z ;
2) Q \ { 0 }, R \ { 0 }, C \ { 0 } . Q*, R*, C*;
3) Q, R, C ;
4) Cn n - ;
5) Aut(M) ᳺ M . M n , ᳺ n , Sn n ;
6) GLn(C) ( ) n x n .
, n , n. - Zn = { } , n. , Å n. r s, n. . Zn Å , n.
Å Z 5:
Å | |||||
G , G .
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, G . , , A = { 1, i} C4 = { 1, -1, i, -i} . i i = -1. A . , A G . A , , , .
B = { 1, 2, , 2 n, } Q *. B, , 1, .
: G , , :
) h1, h2 Î H: h1 h2 Î H;
) h Î H: h- 1Î H.
ij, ) , . , . ) . , ) ) , : h Î H, h- 1Î H h h- 1= Î H.
:
1) G {} G;
2) Z Ì Q Ì R Ì C ;
3) Cn C*. , ;
4) n Sn. ;
5) , 1, GLn(C).
g G , n, gn = e. g O(g).
, C*, O(i) =4, O(cos( 2 p / 5 )+ i sin( 2 p / 5 )) = 5, 2 .
, , .
( 䒺) g G: e, g, g 2, , g- 1, g- 2, . , G. , .
:
1) C 4 = {i, i 2=-1, i 3= -i, i 4=1 } C* i;
2) a Î S 3 a = ( 1, 2 ). a 2= e, a 3= e, a 4= e . ., a- 1= a. , {e, a} S 3;
3) GL 2 (C). , , m Î Z. .
G , g Î G, G.
Cn i Zn. Z 1 ( ). , - .
G, g G. ˳ G ( g) gh, h ; gH. G .
:
1) G = S 3 3 . S 3: e = , a = , b = , c = , d = , a 2 = .
H = { e, a, a 2} S 3.
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S 3 :
◦ | e | a | b | c | d | a 2 |
E | e | a | b | c | d | a 2 |
A | a | a 2 | d | b | c | e |
B | b | c | e | a 2 | d | |
C | c | d | a 2 | e | a | b |
D | d | b | a | a 2 | e | c |
a 2 | a 2 | e | c | d | b | a |
˳ H:
eH ={ e, a, a 2}, aH ={ e, a, a 2}, a 2 H ={ e, a, a 2},
bH ={ b, c, d }, cH ={ b, c, d }, dH ={ b, c, d }.
H:
He ={ e, a, a 2}, Ha ={ e, a, a 2}, Ha 2={ e, a, a 2},
Hb ={ b, c, d }, Hc ={ b, c, d }, Hd ={ b, c, d }.
, eH = He, aH = Ha, bH = Hb, cH = Hc, dH = Hd, a 2 H = Ha 2, .
, :
2) G = S 3, H = {e, b}. ˳ , d, : dH = {de, db} = {d, a}. Hd = {ed, bd} = {d, a 2 }. , dH ¹ Hd;
3) G = Z, H , 5. , 1, 1 + 5 Z = { 1, 15, 125, }. , 5 1.
, 5 Z 5 Z: 5 Z, 1 + 5 Z, 2 + 5 Z, 3 + 5 Z,4 + 5 Z.
H G , G. , g Î G , , gH, g = ge Î gH.
, H n , n . ij, h 1 ¹ h 2, gh 1 ¹ gh 2, gh 1 = gh 2 h 1 = h2.
, gH H . .
.
. .
. : g 1 H Ç g 2 H ¹ Æ g 1 H = g 2 H. g 0 Î g 1 H Ç g 2 H, g 0 = g 1 h 1 = g 2 h 2, h 1, h 2 Î H. g 1 H Í g 2 H. : - h Î H: g 1 h = g 1 (h 1 (h 1 )- 1 )h = g 0 h ' = g 2 h 2 h ' = g 2 h '' Î g 2 H.
, g 2 H Í g 1 H.
. - H G .
. g Î G , gH. . , ᒺ , . j H G. , n = j m, n G; m H. .
. , . . .
, - m n. , A 4 ( S 4) 12 6.
ϳ G , gH = Hg g Î G. , . . g 1 Hg 2 H = (g 1 g2)H. - G G / .
³ f: G 1 G2 (G 1, ) (G 2, *) , - x, y Î G 1, f(x y) = f(x) * f(y).
.
) C 2 = { -1, 1 } . 1·1 = 1, 1·(-1) = (-1)·1 = -1, (-1)·(-1) = 1.
) S 2 . e = ( 1 ), a = ( 1, 2 ). ee = e, ea = ae = a, aa = e.
, . e a, . :
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. ij, = , = = . г , , . , = .
C 2 S 2 ; e i a 1 1. , , .
, . . (G 1, ) = {e 1, a1}, (G 2, * ) = {e 2, a 2 } . ᳺ f: G 1 G 2, f(e 1 ) = e 2, f(a 1 ) = a 2, . , f(e 1 a 1 ) = f(e 1 ) * f(a 1 ), f( 1 a 1 ) = f( 1 ) * f(a 1 ). , f(e 1 a 1 ) = a 2 f( 1 a 1 ) = e 2, f(e 1 ) * f(a 1 ) = e 2 * a 2 = a 2 f( 1 ) * f(a 1 ) = a 2 * a 2 = e 2.
, g: G 1 G 2, g(e 1 ) = 2, g(a 1 ) = 2, . : g( 1 a 1 ) = a 2 g( 1 ) * g(a 1 ) = e 2 * e 2 = e2. , g( 1 a 1 ) ¹ g( 1 ) * g(a 1 ).
f: G 1 G 2 (G1, ) (G 2, *) , - x, y Î G 1, f(x y) = f(x) * f(y).
, G 1 G2 ᳺ G 1 G2 .
G1 i G2 , G 1 G 2; G 1 @ G 2.
, , . , , , ᳺ .
Q+ Q . , ᳺ Q+ Q, . , ᳺ f: Q+ Q, Î Q Î Q+, f( 2 ) = f() = / 2. , f( 2 ) = / 2 + / 2 = = f( 2 ). ᳺ 2 = 2, , - .
: f() (f - ), .
, G={e, a, b}. : e, a, b. ? , . ij, ai aj = ak as aj = ak, ai aj=as aj. ai = as ( i ¹ s), .
2? , b. b . 2 = b. .
b | |||
b | |||
b | |||
b | b |
, , , . . ³, ( C 3 S 3) .
, , , , . , .
a 2 = b, a 3 = c, a 4 = e.
b | c | |||
b | c | |||
b | c | e | ||
b | b | c | e | a |
c | c | e | a | b |
: ? , 2, a2 = b 2 = c 2 = , ( )
b | c | |||
b | c | |||
e | c | b | ||
b | b | c | e | a |
c | c | b | a | e |
b | c | |||
b | c | |||
e | ||||
b | b | e | ||
c | c | e |
, a = ( 1, 2 )( 3, 4 ), b = ( 1, 3 )( 2, 4 ), c = ( 1, 4 )( 2, 3 ), e = ( 1 ). , . .
, .
. - G Aut(G).
. G n, Sn.
, .
ʳ
, + () ∙ (), :
(K1) (K, +) ;
(2) (K, ∙) ;
(3) :
(x + y) z = x z + y z, z (x + y) = z x + z y
x, y, z Î K.
(K, +, ∙) .
(K, +) , (K, ∙) - .
(K, ·) , , (K, +) . ʳ , (K, ∙) ( , ). 0 1 ( ) .
:
1) (Z, +, ∙) ;
2) (Q, +, ∙) ;
3) (R, +, ∙) ;
4) (C, +, ∙) ;
5) n(R) n x n . . R n R. . n > 1, , , n(R) .
ϳ L , - x, y Î L
x + y Î L i x ∙ y Î L.
ϳ L , - x Î L a Î K a ∙ x Î L, x ∙ a Î L.
- , L . - / L (K, +) L ( ) , : (x + L) (y + L) = x ∙ y + L. - L / L.
-, . nZ , n, Z. - Z / nZ = Zn Ä n. r s, n. . Zn Å Ä , n .
Ä Z 5:
Ä | |||||
³ f: 1 2 ( 1, +, ∙) ( 2, Å, Ä) , , - x, y Î 1
f (x + y) = f (x) Å f (y),
f (x ∙ y) = f (x) Ä f (y).
ᳺ , . 1 i 2 , 1 2; 1 @ 2.
, . , .
1 i 2 , .
, , .
. - n , , n . n , , n.
.
Zp .
n . Zp[x] Zp. f(x) n, Zp. (f(x)) , , f(x). - Zp[x] / (f(x)) n . : f(x). : (mod f(x), p).