next up previous
¤U¤@­¶: ±N ring ¬Ý¦¨¬O vector ¤W¤@­¶: ½u©Ê¥N¼ÆªºÀ³¥Î «e¤@­¶: ½u©Ê¥N¼ÆªºÀ³¥Î

½u©Ê¥N¼Æ°ò¥»©Ê½è.

¦b³o¸Ì§Ú­Ì¶È²³æ¦^ÅU¤°»ò¬O vector space, basis ¥H¤Î dimension. §Ú­Ì¤£µ¹³o¨Ç°ò¥»©Ê½èªºµý©ú, ­Y¤£²M·¡ªº¦P¾Ç½Ð°Ñ¦Ò¤@¯ë¦³Ãö½u©Ê¥N¼Æªº®ÑÄy.

Definition 9.3.1   ¥O F ¬O¤@­Ó field. §Ú­Ì»¡ V ¬O¤@­Ó vector space over F, ¦pªG V ¥»¨­¤¸¯À¶¡¦³¥[ªk ``+'' ¹Bºâ, ¦Ó¥B¹ï¥ô·N c $ \in$ F, v $ \in$ V ¬Ò¦³ c . v $ \in$ V, ¥Bº¡¨¬:
(VS1)
V ¦b¥[ªk¤§¤U¬O¤@­Ó abelian group.
(VS2)
¹ï©Ò¦³ªº c $ \in$ F ¥H¤Î v1, v2 $ \in$ V ¬Ò¦³ c . (v1 + v2) = c . v1 + c . v2.
(VS3)
¹ï©Ò¦³ c1, c2 $ \in$ F ¥H¤Î v $ \in$ V ¬Ò¦³ (c1 + c2) . v = c1 . v + c2 . v ¥B c1 . (c2 . v) = (c1 . c2) . v.
(VS4)
¹ï¥ô·N v $ \in$ V ¬Ò¦³ 1 . v = v, ¨ä¤¤ 1 $ \in$ F ¬O F ­¼ªkªº identity.

³o¸Ì­nª`·N¤@¯ë vector space ªº©w¸q¸Ì¨Ã¨S¦³­n¨D F $ \subseteq$ V, ¤]¨S¦³­n¨D V ªº¤¸¯À¶¡¦³­¼ªk¹Bºâ. ¤£¹L±N¨Ó§Ú­Ì°Q½× field ªº©Ê½è®É©Ò¸I¨ìªº vector space ³£·|ÃB¥ ¦³ F $ \subseteq$ V ¥H¤Î V ªº¤¸¯À¶¡¦³­¼ªk¹Bºâ³o¨âºØ¯S©Ê. ¤]´N¬O³o¨âºØ¯S©Ê¨Ï±o field ªº©Ê½è¤ñ¤@¯ëªº vector space ±j±o¦h.

Definition 9.3.2   °²³] F ¬O¤@­Ó field ¥B V ¬O¤@­Ó vector space over F, ¦pªG v1,..., vn $ \in$ V º¡¨¬¹ï¥ô·N v $ \in$ F ¬Ò¦s¦b c1,..., cn $ \in$ F ¨Ï±o

v = c1 . v1 + ... + cn . vn,

«hºÙ v1,..., vn span V over F.

¦pªG¤@­Ó vector space ¦s¦b¤@²Õ v1,..., vn $ \in$ V span V over F, «h§Ú­ÌºÙ V ¬O¤@­Ó finite dimensional vector space over F.

¦pªG v1,..., vn span V over F, ·íµM¤]¦³¥i¯à¦³¥t¤@²Õ w1,..., wm $ \in$ V ¤] span V over F. §Ú­Ì·íµM§Æ±æ¯à§ä¨ì¤@²Õ¤¸¯À³Ì¤Öªº v1,..., vn ¥i¥H span V over F. ­n¹F¨ì³o¤@ÂI v1,..., vn ¤§¶¡¦Ü¤Ö­n¨S¦³½u©ÊÃö«Y, ­n¤£µM¨ä¤¤ªº¬Y­Ó vi ¥i¥H³Q¨ä¥Lªº vj ®i¦¨, §Ú­Ì´N¥i¥H§ä¨ì§ó¤Öªº¤¸¯À span V ¤F. ¦]¦¹§Ú­Ì¦³¥H¤Uªº©w¸q.

Definition 9.3.3   °²³] F ¬O¤@­Ó field ¥B V ¬O¤@­Ó vector space over F, ¦pªG¹ï©ó V ¤¤ªº¤@²Õ¤¸¯À v1,..., vn $ \in$ V §Ú­Ì³£§ä¤£¨ì¤£¥þ¬° 0 ªº c1,..., cn $ \in$ F ¨Ï±o

c1 . v1 + ... + cn . vn = 0,

«hºÙ³o²Õ v1,..., vn ¬O linearly independent over F.

¦pªG v1,..., vn $ \in$ F span V ¥B¬O linearly independent over F, «hºÙ v1,..., vn ¬O¤@²Õ basis of V over F.

½u©Ê¥N¼Æ¤¤³Ì°ò¥»ªº©Ê½è´N¬O·í V ¬O finite dimensional vector space over F ®É, ¤@©w¥i¥H§ä¨ì V over F ªº¤@²Õ basis. ÁöµM basis ¨Ã¤£¬O°ß¤@ªº, ¤£¹L¥ô¤@²Õ basis ¨ä¤¸¯À­Ó¼Æ³£¬O¬Û¦Pªº. ³o­Ó basis ªº­Ó¼ÆºÙ¤§¬° V over F ªº dimension, §Ú­Ì°O¬° dimF(V). ¤]´N¬O»¡­Y dimF(V) = n, «h¥i¥H§ä¨ì¤@²Õ v1,..., vn $ \in$ V ¬O linearly independent over F ¥B span V over F.

¦pªG W $ \subseteq$ V ¥B§Q¥Î V ©M F ¶¡ªº¹Bºâ W ¤]¬O¤@­Ó vector space over F, «hºÙ W ¬O V ªº¤@­Ó subspace over F. ¥H¤U¬O dimension ¤@¨Ç°ò¥»ªº©Ê½è, §Ú­Ì²¤¥hÃÒ©ú.

Lemma 9.3.4   °²³] F ¬O¤@­Ó field ¥B V ¬O¤@­Ó finite dimensional vector space over F.
  1. ­Y v1,..., vn span V over F, «h dimF(V)$ \le$n.
  2. ­Y w1,..., wm $ \in$ F ¬O linearly independent over F, «h dimF(V)$ \ge$m.
  3. ­Y W ¬O V ªº¤@­Ó subspace over F, «h dimF(V)$ \ge$dimF(W).


next up previous
¤U¤@­¶: ±N ring ¬Ý¦¨¬O vector ¤W¤@­¶: ½u©Ê¥N¼ÆªºÀ³¥Î «e¤@­¶: ½u©Ê¥N¼ÆªºÀ³¥Î
Administrator 2005-06-18