·¢²¼Ê±¼ä : ÐÇÆÚÎå ÎÄÕµڶþÕ Ⱥ¸üÐÂÍê±Ï¿ªÊ¼ÔĶÁ
(xyx?1)k?xyx?1?xykx?1?xyx?1 ?x?1xykx?1x?x?1xyx?1x,¼´yk?y.
9.ÉèeÊÇȺGµÄµ¥Î»Ôª,a,bÊÇGµÄÁ½¸öÔªËØ,ÎÊÏÂÁÐÃüÌâÊÇ·ñ³ÉÁ¢?Ϊʲô? (1)(ab)?1?a?1b?1; (2)(ab)?2?b?2a?2; (3)Èôa2?e,Ôòa?a?1.
´ð (1)µ±ab?baʱ,(ab)?1?(ba)?1?a?1b?1,¼´ÃüÌâ(1)³ÉÁ¢.µ±
ab?baʱ,(ab)?1?(ba)?1,¶ø(ba)?1?a?1b?1.Òò´Ë(ab)?1?a?1b?1,¼´ÃüÌâ(1)²»³ÉÁ¢. (2)µ±(ab)2?a2b2ʱ,((ab)2)?1?(a2b2)?1,¼´(ab)?2?b?2a?2,Ò༴ÃüÌâ(2)³ÉÁ¢.µ±
(ab)2?a2b2ʱ,((ab)2)?1?(a2b2)?1,¼´(ab)?2?b?2a?2,Ò༴ÃüÌâ(2)²»³ÉÁ¢.
(3)½«µÈʽa2?eµÄÁ½±ß×ó³Ëa?1¼´µÃa?a?1.Òò´ËÃüÌâ(3)³ÉÁ¢.
¡ì2.3ÔªËصĽ×
1.ÔÚ·ÇÁãÓÐÀíÊý³ËȺQ?ÖÐ,ÇóÏÂÁи÷¸öÊýµÄ½×:
1 (1)1;(2)?1;(3)2;(4).
2 ½â ÓÉÓÚ1ÊÇQ?µÄµ¥Î»Ôª,Òò´Ë1µÄ½×ÊÇ1.ÓÉÓÚ?1?1,(?1)2?1,Òò´Ë?1µÄ½×ÊÇ2.
1ÓÉÓÚ2ºÍµÄÈκÎÕýÕûÊý´ÎÃݶ¼²»µÈÓÚ1,Òò´ËËüÃǵĽ׶¼ÊÇÎÞÏÞ½×ÔªËØ.
2 2.Éèam?e,m?N,Èô?n?Z,ÓÉan?e,¿ÉÒÔÍƳöm|n,Ö¤Ã÷:|a|?m.
Ö¤Ã÷ ÓÉÓÚam?e,Òò´Ë|a|?m.ÓÉÓÚ|a|?ZÇÒa|a|?e,Òò´Ëm||a|.ÓÉÓÚm,|a|?N,Òò´ËÓÉm||a|¿ÉÒÔ¶ÏÑÔm?|a|.ËùÒÔ|a|?m.
3.ÉèGÊÇȺ,a,x?G,Ö¤Ã÷:|a?1|?|a|,|x?1ax|?|a|. Ö¤Ã÷ Áîe±íʾGµÄµ¥Î»Ôª.
¶ÔÓÚÈÎÒâµÄb?GºÍÈÎÒâµÄm?N,ÎÒÃÇÓÐ
bm?e?(b?1)m?bm(b?1)m?(bb?1)m?em?e.
Òò´Ë
|b?1|?|b|.
ÔÚÉÏʽÖÐ,Áîb?a,µÃ
|a?1|?|a|;
Áîb?a?1,µÃ
|a|?|(a?1)?1|?|a?1|.
ËùÒÔ|a?1|?|a|.
Æä´Î,¶ÔÓÚÈÎÒâµÄb,y?GºÍÈÎÒâµÄm?N,ÎÒÃÇÓÐ
17
(y?1by)m?y?1bmy,
´Ó¶ø
bm?e?(y?1by)m?y?1bmy?y?1ey?y?1y?e.
Òò´Ë
|y?1by|?|b|.
ÔÚÉÏʽÖÐ,Áîb?a,y?xµÃ
|x?1ax|?|a|;
Áîb?x?1ax,y?x?1,µÃ
|a|?|x(x?1ax)x?1|?|x?1ax|.
ËùÒÔ|x?1ax|?|a|.
4.ÉèÔÚȺGÖÐ2½×ÔªËØÖ»ÓÐÒ»¸ö,a.Ö¤Ã÷:¶ÔÓÚGÖÐÿһ¸öÔªËØx,¶¼ÓÐax?xa. Ö¤Ã÷ ÈÎÒâ¸ø¶¨x?G.ÕâÑùÒ»À´,¸ù¾ÝÉÏÒ»ÌâµÄ½áÂÛ,ÎÒÃÇÓÐ
|x?1ax|?|a|?2.
ÓÉÓÚGÖÐ2½×ÔªËØÖ»ÓÐÒ»¸ö,Òò´Ëx?1ax?a.Óɴ˿ɼûax?xa. 5.ÉèȺGµÄÿһ¸ö·Çµ¥Î»ÔªµÄÔªËض¼ÊÇ2½×µÄ,Ö¤Ã÷:GÊǽ»»»Èº.
Ö¤Ã÷ Áîe±íʾGµÄµ¥Î»Ôª.ÈÎÒâ¸ø¶¨x,y?G.ÓÉÓÚxyµÄ½×Ö»ÄÜÊÇ1»ò2,Òò´Ë
xyxy?e.
ÓÉÓÚxºÍyµÄ½×Ö»ÄÜÊÇ1»ò2,´Ó¶øx?1?x,y?1?y,Òò´Ë½«ÉÏʽÁ½±ßÓÒ³Ëyx,¿ÉµÃ
xy?yx.ÕâÑùÒ»À´,ÓÉÓÚxºÍyµÄÈÎÒâÐÔ,ÎÒÃÇ¿ÉÒÔ¶ÏÑÔ,GÊǽ»»»Èº. 6.ÉèGÊÇÒ»¸ö·Ç½»»»Èº,Ö¤Ã÷:GÖдæÔڷǵ¥Î»Ôªa,b,ʹµÃab?ba.
Ö¤Ã÷ ÓÉÓÚGÊÇÒ»¸ö·Ç½»»»Èº,¸ù¾ÝÉÏÌâµÄ½áÂÛ,´æÔڽײ»ÊÇ1ºÍ2µÄÔªËØa?G.Áî
b?a?1.ÏÔÈ»aºÍb¶¼²»ÊÇGµÄµ¥Î»Ôª,²¢ÇÒab?ba.
7.ÉèGÊÇÒ»¸öÓÐÏÞ½»»»Èº,mÊÇGµÄÔªµÄ½×ÖÐ×î´óÒ»¸ö,Ö¤Ã÷:GµÄÿһ¸öÔªµÄ½×Õû³ým.
Ö¤Ã÷ Éèa,b?GÇÒ|a|?m,|b|?n.ÏÖÔÚÒªÖ¤Ã÷n|m.Ϊ´Ë,Áîr?(m,n).ÏÔ
nnmnÈ»,|br|?,(,m)?1.ÓÉÓÚGÊǽ»»»Èº,¸ù¾Ý±¾½ÚµÄÀý2,|abr|?|a||br|?.ÒòΪmrrrnmnÊÇGµÄÔªµÄ½×ÖÐ×î´óÒ»¸ö,ËùÒÔ?m,´Ó¶ø?1.Óɴ˿ɼûr?n,¼´(m,n)?n.ËùÒÔ
rrn|m.
8.ÉèGÊÇÒ»¸öÓÐÏÞȺ,Ö¤Ã÷:
(1)ÔÚGÖÐ,½×´óÓÚ2µÄÔªËصĸöÊýÒ»¶¨ÊÇżÊý;
(2)ÔÚGÖÐ,½×µÈÓÚ2µÄÔªËصĸöÊýÓëGµÄ½×ÓÐÏà·´µÄÆæżÐÔ.
Ö¤Ã÷ (1)µ±È»GÊÇÒ»¸ö·Ç¿Õ¼¯ºÏ.ÏÖÔÚÎÒÃǶ¨Ò弯ºÏGÉϵĹØϵRÈçÏÂ:¶ÔÓÚÈÎÒâµÄa,b?G,
aRb?a?b»òa?b?1.
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²»ÄÑÑéÖ¤,RÊǵȼ۹Øϵ.ÁîS±íʾµÈ¼Û¹ØϵRËùÈ·¶¨µÄ¼¯ºÏGµÄ·ÖÀà;¶ÔÓÚÈÎÒâµÄ
a?G,½«ÒÔaΪ´ú±íµÄÀà¼Ç×÷[a].ÈÎÒâ¸ø¶¨a?G.ÏÔÈ»,µ±|a|?2ʱ,|[a]|?1.µ±
|a|?2ʱ,a?1?a,´Ó¶ø,[a]?{a,a?1}.ÕâÑùÒ»À´,µ±GÖÐûÓн״óÓÚ2µÄÔªËØʱ,ÔÚGÖÐ
½×´óÓÚ2µÄÔªËصĸöÊýÊÇ0,Òò¶øÊÇżÊý.µ±GÖÐÓн״óÓÚ2µÄÔªËØʱ,ÓÉÓÚGÊÇÓÐÏÞ¼¯,GÖн״óÓÚ2µÄÈ«ÌåÔªËØ×é³É¼¯ºÏÊÇÓÐÏÞ¸ö»¥²»ÏཻµÄ¶þÔª¼¯µÄ²¢,Òò¶øÔÚGÖн״óÓÚ2µÄÔªËصĸöÊýÊÇżÊý.
(2)ÏÔÈ»,|G|?(GÖн״óÓÚ2µÄÔªËصĸöÊý?1)?GÖн׵ÈÓÚ2µÄÔªËصĸöÊý.ÒòΪ(GÖн״óÓÚ2µÄÔªËصĸöÊý?1)ÊÇÆæÊý,¸ù¾ÝÉÏʽ¿ÉÒÔ¶ÏÑÔ:ÔÚGÖÐ,½×µÈÓÚ2µÄÔªËصĸöÊýÓëGµÄ½×ÓÐÏà·´µÄÆæżÐÔ. 9.Ö¤Ã÷:Ñ»·ÈºÊǽ»»»Èº.
Ö¤Ã÷ ÉèGÊÇÑ»·Èº.²»·Á¼ÙÉèG?(a).ÓÚÊÇ,¶ÔÓÚÈÎÒâµÄx,y?G,´æÔÚm,n?Z,ʹµÃ
x?am,y?an,
´Ó¶ø,
xy?aman?am?n?anam?yx.
ËùÒÔGÊǽ»»»Èº.
10.Éèn|m,Ö¤Ã÷:·½³Ìxn?eÔÚm½×Ñ»·ÈºÖÐÓÐn¸ö½â.
m Ö¤Ã÷ ²»·ÁÉèG?(a)ÊÇm½×Ñ»·Èº.Áîq?.ÏÔÈ»,ÏÂÁÐn¸öÔªËØÊÇ·½³Ìxn?eÔÚ
nGÖеÄn¸ö²»Í¬µÄ½â:
a0,aq,a2q,?,a(n?1)q
ÁíÒ»·½Ãæ,¼ÙÉèak(0?k?m?1)ÊÇ·½³Ìx?eÔÚGÖеĽâ,Ôòm|kn,´Ó¶ø,q|k.Òò´Ë
k?{0,q,2q,?,(n?1)q}.ËùÒÔ·½³Ìxn?eÔÚGÖÐÖ»ÓÐÉÏÊön¸öµÄ½â.
n 11.Çó³ö6´Îµ¥Î»¸ùȺU6µÄÿһ¸öÔªËصĽ×ÓëËùÓÐÉú³ÉÔª.
½â U6?(¦Å),ÆäÖЦÅ?ei2¦Ð6.ÓÉÓÚ
|?0|?1,|¦Å|?6,|¦Å2|?3,|¦Å3|?2,|¦Å4|?3,|?5|?6.
Òò´ËÖ»ÓЦźͦÅ5ÊÇU6µÄÉú³ÉÔª.
¡ì2.4×ÓȺ
1.ÉèGÊǽ»»»Èº,Ö¤Ã÷:GµÄËùÓÐÓÐÏÞ½×ÔªËصļ¯ºÏ×÷³ÉGµÄ×ÓȺ.
Ö¤Ã÷ ÁîH±íʾGµÄËùÓÐÓÐÏÞ½×ÔªËصļ¯ºÏ,e±íʾµÄµ¥Î»Ôª.ÏÔÈ»e?H,´Ó¶ø
H??.Éèa,b?H.ÓÚÊÇ´æÔÚÕýÕûÊým,n,ʹµÃ
|a|?m,|b|?n,
19
´Ó¶ø
(ab?1)mn?(am)n((bn)m)?1?en(em)?1?e.
Òò´Ëab?1?H.ËùÒÔH¡ÜG. 2.ÉèGÊÇȺ,??S?G,Áî
CG(S)?{x?G|xs?sx,?s?S}.
Ö¤Ã÷:CG(S)¡ÜG.(CG(S)³ÆΪSÔÚGÄÚµÄÖÐÐÄ»¯×Ó.)
Ö¤Ã÷ Áîe±íʾµÄµ¥Î»Ôª.ÏÔÈ»e?CG(S),´Ó¶øCG(S)??.Éèx,y?CG(S).ÎÒÃÇÓÐ
(xy)s?x(ys)?x(sy)?(xs)y?(sx)y?s(xy),?s?S;
sx?xs,?s?S,
´Ó¶ø(½«ÉÏʽÁ½±ß×ó³Ëx?1,ÓÒ³Ëx?1),
x?1s?sx?1,?s?S.
Òò´Ëxy,x?1?CG(S).ËùÒÔCG(S)¡ÜG.
2.ÉèGÊÇȺ,??S?G,Áî
NG(S)?{x?G|xS?Sx}.
Ö¤Ã÷:NG(S)¡ÜG.(NG(S)³ÆΪSÔÚGÄÚµÄÕý¹æ»¯×Ó.)
Ö¤Ã÷ Áîe±íʾµÄµ¥Î»Ôª.ÏÔÈ»e?NG(S),´Ó¶øNG(S)??.Éèx,y?NG(S).ÎÒÃÇÓÐ
(xy)S?x(yS)?x(Sy)?(xS)y?(Sx)y?S(xy);
Sx?xS,
´Ó¶ø(½«ÉÏʽÁ½±ß×ó³Ëx?1,ÓÒ³ËxNG(S)¡ÜG.
?1),x?1S?Sx?1.Òò´Ëxy,x?1?NG(S).ËùÒÔ
4.ÉèT±íʾÊýÓòPÉÏÈ«Ìån½×ÉÏÈý½Ç¾ØÕó×é³ÉµÄ¼¯ºÏ,D±íʾÊýÓòPÉÏÈ«Ìån½×¶Ô½Ç¾ØÕó×é³ÉµÄ¼¯ºÏ,S±íʾÊýÓòPÉÏÈ«Ìån½×¶Ô³Æ¾ØÕó×é³ÉµÄ¼¯ºÏ,Ö¤Ã÷:T,D,S¶¼ÊÇÊýÓòPÉÏn½×¾ØÕó¼ÓȺ(Mn(P),?)µÄ×ÓȺ. Ö¤Ã÷ ÏÔÈ».
5.ÉèO±íʾÊýÓòPÉÏÈ«Ìån½×Õý½»¾ØÕó×é³ÉµÄ¼¯ºÏ,Ö¤Ã÷:OÊÇÒ»°ãÏßÐÔȺ
GL(n,P)µÄ×ÓȺ.
Ö¤Ã÷ ÖÚËùÖÜÖª,GL(n,P)ÖÐÔªËصij˷¨¾ÍÊǾØÕóµÄ³Ë·¨,¶ÔÓÚÈÎÒâµÄ
A?GL(n,P),AµÄÄæÔª¾ÍÊÇAµÄÄæ¾ØÕó.ÕâÑùÒ»À´,ÓÉÓÚÊýÓòPÉϵÄn½×µ¥Î»¾ØÕóÊÇÊý
ÓòPÉϵÄÕý½»¾ØÕó,ÊýÓòPÉϵÄÈÎÒâÁ½¸ön½×Õý½»¾ØÕóµÄ³Ë»ýÈÔÊÇÊýÓòPÉϵÄn½×Õý½»¾ØÕó,ÊýÓòPÉϵÄÈÎÒâÒ»¸ön½×Õý½»¾ØÕóµÄÄæ¾ØÕóÈÔÊÇÊýÓòPÉϵÄn½×Õý½»¾ØÕó,Òò´Ë
OÊÇÒ»°ãÏßÐÔȺGL(n,P)µÄ×ÓȺ. 6.ÉèH,K¶¼ÊÇGµÄ×ÓȺ,Ö¤Ã÷:
(H?K)a?Ha?Ka,?a?G.
Ö¤Ã÷ ÈÎÒâ¸ø¶¨a?G.ÏÔÈ»,¶ÔÓÚÈÎÒâµÄx?G,ÎÒÃÇÓÐ
20