В.А. Артамонов - Лекции по алгебре, 3 семестр, мех-мат МГУ (1106002), страница 10
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à G̃, N ®¯à¥¤¥«¥ ¥®à¥¬ 6.26.£à㯯 ¨, ¨®¤®§ ç®.¯à¥¤¥«¥¨¥ 6.27. à㯯 G̃ §ë¢ ¥âáﮤ®á¢ï§ë¬ ªàë⨥¬à¨¬¥àë 6.28. «¥¤ãî騥 £àã¯¯ë ®¤®á¢ï§ë:SL(n, C),SU(n, C),Spin(n, C).¬¥îâáï á«¥¤ãî騥 ®¤®á¢ï§ë¥ ªàëâ¨ï:(1)(2)(3)(4)(5)R → U(1, C);SL(2, C) → SO(3, C);SU(2, C) → SO(3, R);SL(2, C) × SL(2, C) → SO(4, C);SL(4, C) → SO(6, C).ਠí⮬ ¢ ᨫ㠥¤¨á⢥®á⨠ªàëâ¨ïSpin(3, C) ' SL(2, C), Spin(4, C) ' SL(2, C) × SL(2, C),Spin(6, C) ' SL(4, C).G.546. Å 3. ।áâ ¢«¥¨ï £à㯯 ¨¥®à¥¬ 6.29.
ãáâì G ª®¬¯ ªâ ï £à㯯 ¨. ®£¤ G áãé¥áâ¢ã¥â ¨ ¥¤¨áâR¢¥ë© â ª®© ¨â¥£à « G f (g)dg ¤«ï ª ¦¤®© «¨â¨ç¥áª®© äãªæ¨¨ f G, çâ® ®(1)(2)(3)«¨¥¥®â®á¨â¥«ì®äãªæ¨¨ f ;RR2dg=1,|f(g)|dg>0, ¥á«¨ f 6= 0;GGRGf (g)dg =R«¥¤á⢨¥ 6.30.Gf (g −1 )dg =RGf (gh)dg =RGf (hg)dg , ¥á«¨ h ∈ G.î¡®¥ ª®¥ç®¬¥à®¥ ¯à¥¤áâ ¢«¥¨¥ ª®¬¯ ªâ®© £àã¯¯ë ¨¢¯®«¥ ¯à¨¢®¤¨¬®.«¥¤á⢨¥ 6.31. ãáâì § ¤ ® ¯à¥¤áâ ¢«¥¨¥ φ : G → GL(V ), £¤¥ dim V¢¢®¤¨âáï ᪠«ï஥ ¯à®¨§¢¥¤¥¨¥ (x, y).
¢¥¤¥¬ ®¢®¥ ᪠«ï஥ ¯à®¨§¢¥¤¥¨¥< ∞. Zhx, yi =(φ(g)x, φ(g)y)dg.G ᨫã ᢮©á⢠¨â¥£à « ª ¦¤ë© ®¯¥à â®àφ(h), h ∈ G, ã¨â à¥.¥®à¥¬ 6.32. î¡®¥ ¥¯à¨¢®¤¨¬®¥ ª®¬¯«¥ªá®¥ ¯à¥¤áâ ¢«¥¨¥ ª®¬¯ ªâ®© £àã¯¯ë ¨ ª®¥ç®¬¥à®.¥®à¥¬ 6.33. à㯯 ¢á¥å ã¨â àëå ¬ âà¨æ U(n, C) ï¥âáï ¬ ªá¨¬ «ì®© ª®¬¯ ªâ®© ¯®¤£à㯯®© ¢ GL(n, C). î¡ ï ¤àã£ ï ¬ ªá¨¬ «ì ï ª®¬¯ ªâ ï ¯®¤£à㯯 ¢GL(n, C) ᮯà殮 á U(n, C). à㯯 ¢á¥å ®à⮣® «ìëå ¬ âà¨æ O(n, R) ï¥âáï¬ ªá¨¬ «ì®© ª®¬¯ ªâ®© ¯®¤£à㯯®© ¢ GL(n, R).
î¡ ï ¤àã£ ï ¬ ªá¨¬ «ì ï ª®¬¯ ªâ ï ¯®¤£à㯯 ¢ GL(n, R) ᮯà殮 á O(n, R).¯à¥¤¥«¥¨¥ 6.34. à㯯 ¨¯®«ã¯à®áâ ,¥á«¨ ¢ ¥© ¥â ¥¥¤¨¨çëå á¢ï§ëå®à¬ «ìëå ¡¥«¥¢ëå ¯®¤£à㯯.ਬ¥à 6.35. à㯯륮६ 6.36.SL(n, C), SU(n, C), SO(3, R)¯®«ã¯à®áâë.î¡ ï á¢ï§ ï ¯®«ã¯à®áâ ï £à㯯 ¨ ¤®¯ã᪠¥â â®ç®¥ «¨¥©®¥¯à¥¤áâ ¢«¥¨¥.¯à¥¤¥«¥¨¥ 6.37. ªá¨¬ «ìë¬ â®à®¬GC∗ .¢ £à㯯¥ ¨¯®¤£à㯯 ¨, ïîé ïáï ¯àï¬ë¬ ¯à®¨§¢¥¤¥¨¥¬ £à㯯 §ë¢ ¥âáï ¬ ªá¨¬ «ì ïਬ¥àë 6.38. ªá¨¬ «ìë© â®à¢¢¢GL(n, C) { ¯®¤£à㯯 ¤¨ £® «ìëå ¬ âà¨æ D(nC),SL(n, C) { ¯®¤£à㯯 ¤¨ £® «ìëå ¬ âà¨æ D(nC) ∩ SL(n, C),SO(n, C) { ¯®¤£à㯯 ¤¨ £® «ìëå ¬ âà¨æ D(nC) ∩ SO(n, C).¥®à¥¬ 6.39.
á¢ï§®© ª®¬¯ ªâ®© £à㯯¥ ¨ ¬ ªá¨¬ «ìë© â®à ï¥âáï ¬ ªá¨¬ «ì®© á¢ï§®© ª®¬¬ãâ ⨢®© ¯®¤£à㯯®© ¨. ᥠ⠪¨¥ ¯®¤£à㯯ë ᮯà殮ë.¯à¥¤¥«¥¨¥ 6.40. ªá¨¬ «ì ï á¢ï§ ï à §à¥è¨¬ ï ¯®¤£à㯯 ¨¨G §ë¢ ¥âáï ¬¥â¨¬, çâ®GB+ᮤ¥à¦¨â ¬ ªá¨¬ «ìë© â®àH.ᥠ¯®¤£àã¯¯ë ®à¥«ïᮯàï¦¥ë ¬¥¦¤ã ᮡ®© ¢ G.G = GL(n, C), â® B + = T (n, C).SU(n, C), â® B + = T (n, C) ∩ G.ਬ¥àë 6.42. ᫨SO(n, C),¢ £à㯯¥¯®¤£à㯯®© ®à¥«ï.¥®à¥¬ 6.41 (®à®§®¢, ®à¥«ì).£àã¯¯ë ¨B+SL(n, C),B + á¢ï§®© ª®¬¯«¥ªá®© ᫨G{ ®¤ ¨§ £à㯯3. ¯à¥¤¥«¥¨¥ 6.43. ãáâìG.«ï «î¡®£® £®¬®¬®à䨧¬ φ : G → GL(n, C) { ª®¬¯«¥ªá®¥ ¯à¥¤áâ ¢«¥¨¥ £àã¯¯ë ¨χ : G → C∗ ç¥à¥§ Vχ ®¡®§ 稬 ¯®¤¯à®áâà á⢮Vχ = {v ∈ V |φ(g)v = χ(g)v¥ã«¥¢®¥ ¯®¤¯à®áâà á⢮¢¥á®¢ë¬¨, ᫨ äãªæ¨ïHχVχ55 §ë¢ ¥âáï¤«ï «î¡®£®g ∈ G}.¢¥á®¢ë¬, ¥ã«¥¢ë¥¢¥á®¬.¢¥ªâ®àë ¨§Vχ §ë¢ îâáï¢ í⮬ á«ãç ¥ §ë¢ ¥âáï{ ¬ ªá¨¬ «ìë© â®à ¢G, â® Hï¥âáï ª®¬¯ ªâ®© ¡¥«¥¢®© £à㯯®©.
«¥¤®-¢ ⥫ì®, ¢á¥ ¥¥ ¥¯à¨¢®¤¨¬ë¥ ¯à¥¤áâ ¢«¥¨ï ®¤®¬¥àë. ®í⮬㠥᫨ § ¤ ® ª®¥ç®¬¥à®¥ ¯à¥¤áâ ¢«¥¨¥â®à®¬H,φ : G → GL(V )á¢ï§®© ª®¬¯ ªâ®© £àã¯¯ë ¨Gá ¬ ªá¨¬ «ìë¬â®V = ⊕sj=1 Vλj (H).¯à¥¤¥«¥¨¥ 6.44. ¥á®¢®© ¢¥ªâ®àª ¦¤®£® í«¥¬¥â g ∈ B+v ∈ Vj \ 0 ¤«ï H §ë¢ ¥âáï áâ à訬,χg ∈ C, çâ® φ(g)v = χg v .¥á«¨ ¤«ï ©¤¥âáï â ª®¥ ç¨á«® ç áâ®áâ¨, áâ à訩 ¢¥á § ¤ ¥â £®¬®¬®à䨧¬χ : B + → C∗ .¥®à¥¬ 6.45.
¥¯à¨¢®¤¨¬®¥ ª®¥ç®¬¥à®¥ ¯à¥¤áâ ¢«¥¨¥ á¢ï§®© ¯®«ã¯à®á⮩ «£¥¡à ¨ç¥áª®© £à㯯ë G ®¤®§ ç®, á â®ç®áâìî ¤® íª¢¨¢ «¥â®á⨠®¯à¥¤¥«ï¥âáï ᢮¨¬ áâ à訬 ¢¥á®¬.G = SL(2, C).ਬ¥à 6.46. ãáâì¯à®áâà á⢥Pn®£¤ ¨¬¥¥âáï ¥áâ¥á⢥®¥ ¯à¥¤áâ ¢«¥¨¥®¤®à®¤ëå ª®¬¯«¥ªáëå ¬®£®ç«¥®¢ ®â®à¥«¥¢áª ï ¯®¤£à㯯 á⥯¥¨n,G¢¨¬¥®,a b◦ f (X, Y ) = f (aX + bY, cX + dY ).c dB+á®á⮨⠨§ ¢á¥å ¢¥àå¥âà¥ã£®«ìëå ¬ âà¨æB=a b,0 dâ à訩 ¢¥ªâ®à í⮣® ¯à¥¤áâ ¢«¥¨ï {¥£ª® ¢¨¤¥âì, çâ®X, Y−Ea, d ∈ C∗ ,Y n,â ª ª ªb ∈ C.B ◦ Y n = a−n Y n .¤¥©áâ¢ã¥â ¯à¨ í⮬ ¯à¥¤áâ ¢«¥¨¨ ⮦¤¥á⢥®, ¥á«¨«¥¤®¢ ⥫ì®, ¯à¨ ç¥â®¬n = 2knç¥â®.¯®«ãç ¥âáï ¥¯à¨¢®¤¨¬®¥ ¯à¥¤áâ ¢«¥¨¥SO(3, C) ' SL(2, C)/{±E}á⥯¥¨2k + 1.ਬ¥à 6.47. ãáâìPnª ª ¨ ¢ëè¥. ¬¥â¨¬, çâ®SU(2, C)á®á⮨⠨§ ¢á¥å ¬ âà¨æ¢¨¤ a −b,b aa, b ∈ C,|a|2 + |b|2 = 1.SU(2, C) ¢ Pn ª ª ®£à ¨ç¥¨¥ ¯à¥¤áâ ¢«¥¨ï SL(2, C) ¨§ ¯à¨SU(2, C).
®«ãç ¥âáï ¥¯à¨¢®¤¨¬®¥ ¯à¥¤áâ ¢«¥¨¥ SU(2, C) ᮯ।¥«¨¬ ¯à¥¤áâ ¢«¥¨¥¬¥à 6.46 ¯®¤£à㯯ãáâ à訬 ¢¥ªâ®à®¬X n.¥©á⢨⥫ì®,B + = SU(2, C) ∩ T (2, C) =a 0|a ∈ C,0 a|a| = 1 ,¨ ¯®í⮬ãਠç¥â®¬2k + 1.a 0◦ X n = an X n .0 an = 2k ¯®«ãç ¥âáï ¥¯à¨¢®¤¨¬®¥ ª®¬¯«¥ªá®¥ ¯à¥¤áâ ¢«¥¨¥ SO(3, R) á⥯¥¨566. Š।áâ ¢«¥¨¥ ¨§ ¯à¨¬¥à 6.47 ¬®¦® ®¯¨á âì ¯®-¤à㣮¬ã.
ãáâì¢á¥å ®¤®à®¤ëå ª®¬¯«¥ªáëå ¬®£®ç«¥®¢fá⥯¥¨n,Hn{ ¯à®áâà á⢮㤮¢«¥â¢®àïîé¨å ¤¨ää¥à¥æ¨- «ì®¬ã ãà ¢¥¨î∆f = 0,∆=SO(3, R) ¨¤ãæ¨à®¢ ® ¥áâ¥áâ¢¥ë¬ ¤¥©á⢨¥¬ ª®®à¤¨ â å âà¥å¬¥àëå ¢¥ª2n + 1 ¤ R, ¨ ®® íª¢¨¢ «¥â® ¯à¥¤áâ ¢«¥¨î ª¨¬ ®¡à §®¬, ¯®«ãç îâáï ¢á¥ ¥¯à¨¢®¤¨¬ë¥ ¯à¥¤áâ ¢«¥¨ï SO(3, R).¥©á⢨¥â®à®¢. â® ¯à¥¤áâ ¢«¥¨¥ ¨¬¥¥â á⥯¥ì¢Pn .∂2∂2∂2+ 2 + 2.2∂x∂y∂z.