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¤U¤@­¶: ¥Ñ Ring ªº©w¸q©Ò±oªº©Ê½è ¤W¤@­¶: ªì¯Å Ring ªº©Ê½è «e¤@­¶: ªì¯Å Ring ªº©Ê½è

Ring ªº°ò¥»©w¸q

Ring ªºµ²ºc¤ñ Group Â×´I, ¥¦¥²¶·¦³¨âºØ¹Bºâ. ¤@¯ë§Ú­Ì¤À§O¥Î¡u+¡v©M¡u . ¡vªí¥Ü¦¹¤G¹Bºâ. ¨ä¤¤¦b + ªº¹Bºâ¤U§Ú­Ì­n¨D¬O¤@­Ó abelian group, ¦Ó . ªº¹Bºâ¶È­n¨D«Ê³¬©Ê©Mµ²¦X²v. ·íµM¤F¦pªG³o¨âºØ¹Bºâ¨S¦³¬Æ»òÃöÁp, ¨º´N¨S¬Æ»ò·N«ä¤F. §Ú­Ì»Ý­n¤À°t²v (distributive laws) ¨Ó±N¥¦­Ì³sµ²¦b¤@°_.

Definition 5.1.1   ¤@­Ó¶°¦X R ¤¤¦pªG¦³ + ©M . ¨âºØ¹Bºâ¥B²Å¦X¥H¤U©Ê½è, «hºÙ¤§¬°¤@­Ó ring:
(R1)
¹ï¥ô·Nªº a, b $ \in$ R ¬Ò¦³ a + b $ \in$ R.
(R2)
¹ï¥ô·Nªº a, b, c $ \in$ R ¬Ò¦³ (a + b) + c = a + (b + c).
(R3)
¦b R ¤¤¦s¦b¤@¤¸¯À©w¤§¬° 0 º¡¨¬¹ï¥ô·Nªº a $ \in$ R ¬Ò¦³ a + 0 = 0 + a = a.
(R4)
µ¹©w R ¤¤¥ô¤@¤¸¯À a, ¦b R ¤¤¬Ò¦s¦b¤@¤¸¯À b º¡¨¬ a + b = b + a = 0.
(R5)
¹ï¥ô·Nªº a, b $ \in$ R ¬Ò¦³ a + b = b + a.
(R6)
¹ï¥ô·Nªº a, b $ \in$ R ¬Ò¦³ a . b $ \in$ R.
(R7)
¹ï¥ô·Nªº a, b, c $ \in$ R ¬Ò¦³ (a . b) . c = a . (b . c).
(R8)
¹ï¥ô·Nªº a, b, c $ \in$ R ¬Ò¦³ a . (b + c) = a . b + a . c ¥B (b + c) . a = b . a + c . a.

(R1) ¨ì (R5) §i¶D§Ú­Ì R ¦b¥[ªk (+) ¹Bºâ¤U¬O¤@­Ó abelian group. ©Ò¥H¦b group ¤¤ªº¤@¨Ç°ò¥»²z½×§Ú­Ì³£¥i¥Hª½±µ®M¥Î. ¤ñ¤è»¡ 0 ¬O R ¤¤°ß¤@²Å¦X a + 0 = 0 + a = a ªº¤¸¯À (Proposition 1.2.1), ¥H¤Îµ¹©w a $ \in$ R ¥u¦s¦b°ß¤@ªº b $ \in$ R º¡¨¬ a + b = b + a = 0 (Proposition 1.2.2). ¨Ì²ßºD§Ú­Ì±N¦¹ b °O°µ - a. ÁÙ¬O­n±j½Õ¤@¤U³o¸Ìªº 0 ¨Ã¤£¤@©w¬O¤j®a±`¬Ý¨ì¾ã¼Æ©Î¹ê¼Æ¤Wªº 0, ¦Ó - a ¤]¶Èªí¥Ü¬° a ªº¥[ªk¤§ inverse, ¨Ã¨S¦³¤@¯ë¥¿­t¸¹ªº·N¸q.

§Ú­Ì¦C¥X¤@¨Ç group ªº©Ê½è¤è«K¥H«áª½±µ¤Þ¥Î.

Lemma 5.1.2   °²³] R ¬O¤@­Ó ring, «h:
  1. ¹ï¥ô·Nªº a $ \in$ R, - (- a) = a.
  2. ­Y a, b $ \in$ R «h¦s¦b¤@­Ó°ß¤@ªº c $ \in$ R º¡¨¬ a + c = b.

µý ©ú. ½Ð°Ñ¦Ò Theorem 1.2.3 ¤Î Corollary 1.2.5. $ \qedsymbol$

¦A¦¸±j½Õ - (- a) = a ªº©Ê½è¶Èªí¥Ü - a ¦b¥[ªk¤§¤Uªº inverse ¬° a, ¨Ã¨S¦³ `­t­t±o¥¿' ªº·N«ä.

(R6) ©M (R7) »¡©ú R ¤¤­¼ªk ( . ) ³o­Ó¹Bºâ¥»¨­ªº­n¨D. ª`·N³o¸Ì§Ú­Ì¨Ã¥¼­n¨D­¼ªkªº identity ¥²¶·¦s¦b. ¤£¹L­Y¤@­Ó ring ¹ï©ó­¼ªk¨ä identity ¦s¦bªº¸Ü, §Y¨Ï¦b­¼ªk¤§¤U R ¤£¤@©w·|¬O¤@­Ó group ¦ý§Q¥Î©M Proposition 1.2.1 ¬Û¦Pªºµý©ú§Ú­Ì¥iª¾¦¹ identity ¥²°ß¤@. ²ßºD¤W§Ú­Ì·|¥Î 1 ¨Óªí¥Ü³o¤@­Ó­¼ªk¤Wªº identity (ª`·N: ³o¸Ìªº 1 ¨Ã¤£¤@©w¬O¤j®a±`¬Ý¨ì¾ã¼Æ©Î¹ê¼Æ¤Wªº 1). ¦pªG¤@­Ó ring R ¨ä­¼ªkªº identity ¦s¦b, ¨º»ò§Ú­Ì´N·|¯S§O»¡©ú¦ÓºÙ R ¬O¤@­Ó ring with 1.

¥t¥  (R6) ©M (R7) ¤]¨S­n¨D a . b = b . a. ¦pªG¤@­Ó ring R ¤¤¹ï©Ò¦³ªº a, b $ \in$ R ¬Òº¡¨¬ a . b = b . a, §Ú­Ì¤]·|¯S§O»¡©ú¦ÓºÙ R ¬O¤@­Ó commutative ring (ª`·N: ¤£¬O abelian ring ³o­Ó¦WºÙ). ¦b¤j¾Çªº°ò¦¥N¼Æ¤¤§Ú­Ì·|¤ñ¸û±Mª`©ó commutative ring with 1 ³o¤@ºØ ring.

³Ì«á (R8) ´N¬Oµ²¦X ring ªº¥[ªk©M­¼ªkªº¾ô¼Ù. ¤]¬O¦]¬°¥¦Åý ring ¾Ö¦³«Ü¦hº«Gªº©Ê½è, §Ú­Ì¦b¤U¤@¸`·|¬Ý¨ì¤@¨Ç§Q¥Î (R8) ©Ò±oªº ring ªº©Ê½è. ³o¸Ì­nª`·Nªº¬O ring ¤£¤@©w¬O commutative ring, ©Ò¥H¹ï©ó¨âÃ䪺¤À°t²v§Ú­Ì³£­n­n¨D.


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¤U¤@­¶: ¥Ñ Ring ªº©w¸q©Ò±oªº©Ê½è ¤W¤@­¶: ªì¯Å Ring ªº©Ê½è «e¤@­¶: ªì¯Å Ring ªº©Ê½è
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