253:
243:
222:
191:
1028:(i.e. the unnecessary double op) makes it seem like there is an error here. Was the intention to define Quiv as the category of pre-sheaves on Q (i.e. objects covariant functors Q^op \to Set)? If that wasn't the case, why not just reverse the arrows on the category Q to make the introduction of the word pre-sheaves seem a little less awful?
991:
In this article, I see a lot of statements about quivers which presume knowledge about what a quiver is, but I don't see any definition. What is the difference between a quiver and a directed multigraph? If there is none, why is there a separate article about quivers? This article seems to be mainly
1027:
The last line in this section--'Note that Quiv is the category of presheaves on the opposite category Q^op.'--is confusing. Given that pre-sheaves on Q^op would be the category of contravariant set-valued functors on Q^op, which are just covariant set valued functors on Q, this convoluted language
550:
For infinite Γ the algebra is said to "have enough units" in wisbauer's text. It's pretty similar to the "ring" of finite dimensional matrices (those that act as 0 on all but a finite dimensional space). The identity matrix isn't included, but every finite dimensional identity matrix is, and for
510:
A lot of it works if K is a artinian semisimple ring, but beyond that most of the classification differs a great deal. If K is self-injective and noetherian, then there is a nice description of injective and projective objects, but there is no longer any nice theory of gabriel roiter on finite
511:
representation type. If K has finite injective dimension, then work of enochs and herzog gives a reasonable picture of the injective and projective objects for neotherian quivers. In general though (general ring, general quiver) it is a complete mess.
571:
When the multiplication is defined by concatenation, what is the addition of two paths in the path algebra? Perhaps you can add the explanation in the article. It would help me a lot to understand the definition of a path algebra. Thank you.
153:
546:
The sum of the vertices. This is hard to see from the wikipedia article since its description of paths seems to suggest they have length at least 1, but the definition really intends to include paths of length
331:
Multiplying paths together doesn't sound very well defined, unless
Quivers carry a natural structure for multiplying them, which would make them almost identical to categories, except without identity elements.
927:
992:
about quiver algebras and quiver representations, so shouln't there be two separate articles about those topics? Also, "head" and "tail" are undefined - I assume it means "target" and "source" of an edge. --
811:
706:
309:
335:
The multiplication structure is perfectly natural -- it's concatenation. Observe that there are no commutativity restrictions, so quivers have quite a lot less structure than categories.
634:
147:
739:
379:
Actually the correct word here is not path but walk, since we allow the 'path' to visit vertices more than once. See the definitions of walks and paths in graph theory.
458:
418:
950:
970:
438:
44:
1063:
299:
79:
1058:
275:
993:
531:
Can someone clarify for me the statement in the introductory paragraph regarding unit elements? If Γ is finite, what is the unit element? --
85:
1035:
973:
496:
587:
The path algebra kQ is a vector space with basis elements: addition is done in exactly the same way as for any other vector space. If
386:
816:
266:
227:
168:
135:
99:
30:
104:
20:
74:
202:
65:
495:
What if K is a ring, not a field? Most of the statements in the article do not seem to require that K be a field...
129:
744:
639:
997:
125:
1039:
977:
500:
190:
109:
577:
390:
345:
Well, so in order to avoid further misunderstandings, I'll just replace "composition" by concatenation. -
175:
590:
556:
536:
516:
480:
369:
208:
252:
1031:
382:
24:
532:
161:
55:
274:
on
Knowledge. If you would like to participate, please visit the project page, where you can join
258:
70:
551:
lots of arguments this suffices. In PDE type areas, you talk about compact operators and such.
242:
221:
141:
711:
51:
972:" but if someone wants to incorporate the above explanation into the article, please do so.
552:
512:
476:
465:
443:
403:
365:
1012:
573:
469:
394:
373:
360:
It would be great if someone could include the definition of what a path in a quiver is.
932:
955:
423:
1052:
336:
346:
461:
271:
1043:
1016:
1001:
981:
581:
560:
540:
520:
504:
484:
349:
339:
1008:
248:
922:{\displaystyle x+y=(a_{1}+b_{1})p_{1}+(a_{2}+b_{2})p_{2}+\dots }
184:
15:
636:
are all the paths in Q, then a typical element of kQ is
160:
958:
935:
819:
747:
714:
642:
593:
446:
426:
406:
270:, a collaborative effort to improve the coverage of
964:
944:
921:
805:
733:
700:
628:
452:
432:
412:
33:for general discussion of the article's subject.
806:{\displaystyle y=b_{1}p_{1}+b_{2}p_{2}+\dots }
701:{\displaystyle x=a_{1}p_{1}+a_{2}p_{2}+\dots }
174:
8:
952:is the vector space with basis all paths in
400:In the second paragraph, there is a quiver
188:
1029:
216:
957:
934:
907:
894:
881:
865:
852:
839:
818:
791:
781:
768:
758:
746:
719:
713:
686:
676:
663:
653:
641:
611:
598:
592:
445:
425:
405:
218:
929:. This is expressed by the statement "
440:is mentioned. Is this supposed to be
7:
264:This article is within the scope of
629:{\displaystyle p_{1},p_{2},\dots ,}
207:It is of interest to the following
23:for discussing improvements to the
447:
407:
14:
1064:Low-priority mathematics articles
491:What if K is a ring, not a field?
420:, but then another object called
284:Knowledge:WikiProject Mathematics
1059:Start-Class mathematics articles
287:Template:WikiProject Mathematics
251:
241:
220:
189:
45:Click here to start a new topic.
304:This article has been rated as
900:
874:
858:
832:
340:22:29, 27 September 2006 (UTC)
1:
1023:Category-theoretic definition
561:06:40, 20 December 2008 (UTC)
541:15:06, 13 December 2008 (UTC)
521:06:40, 20 December 2008 (UTC)
485:06:41, 20 December 2008 (UTC)
374:06:40, 20 December 2008 (UTC)
278:and see a list of open tasks.
42:Put new text under old text.
1002:09:37, 7 December 2011 (UTC)
982:17:06, 5 December 2010 (UTC)
470:04:07, 4 December 2008 (UTC)
364:(Somebody did this, but...)
1017:22:41, 19 August 2012 (UTC)
582:00:00, 5 January 2010 (UTC)
395:17:43, 5 January 2012 (UTC)
50:New to Knowledge? Welcome!
1080:
734:{\displaystyle a_{i}\in k}
350:10:44, 15 March 2007 (UTC)
1044:14:50, 10 June 2019 (UTC)
987:Where is the definition?!
567:Addition in path algebra?
303:
236:
215:
80:Be welcoming to newcomers
310:project's priority scale
505:11:27, 4 May 2008 (UTC)
453:{\displaystyle \Gamma }
413:{\displaystyle \Gamma }
355:
267:WikiProject Mathematics
966:
946:
923:
807:
735:
702:
630:
454:
434:
414:
197:This article is rated
75:avoid personal attacks
967:
947:
924:
808:
736:
703:
631:
455:
435:
415:
100:Neutral point of view
956:
933:
817:
745:
712:
640:
591:
475:Yes. This is fixed.
444:
424:
404:
290:mathematics articles
105:No original research
25:Quiver (mathematics)
962:
945:{\displaystyle kQ}
942:
919:
803:
731:
698:
626:
450:
430:
410:
259:Mathematics portal
203:content assessment
86:dispute resolution
47:
1046:
1034:comment added by
965:{\displaystyle Q}
433:{\displaystyle Q}
385:comment added by
324:
323:
320:
319:
316:
315:
183:
182:
66:Assume good faith
43:
1071:
971:
969:
968:
963:
951:
949:
948:
943:
928:
926:
925:
920:
912:
911:
899:
898:
886:
885:
870:
869:
857:
856:
844:
843:
812:
810:
809:
804:
796:
795:
786:
785:
773:
772:
763:
762:
740:
738:
737:
732:
724:
723:
707:
705:
704:
699:
691:
690:
681:
680:
668:
667:
658:
657:
635:
633:
632:
627:
616:
615:
603:
602:
459:
457:
456:
451:
439:
437:
436:
431:
419:
417:
416:
411:
397:
292:
291:
288:
285:
282:
261:
256:
255:
245:
238:
237:
232:
224:
217:
200:
194:
193:
185:
179:
178:
164:
95:Article policies
16:
1079:
1078:
1074:
1073:
1072:
1070:
1069:
1068:
1049:
1048:
1025:
994:132.231.198.153
989:
954:
953:
931:
930:
903:
890:
877:
861:
848:
835:
815:
814:
787:
777:
764:
754:
743:
742:
715:
710:
709:
682:
672:
659:
649:
638:
637:
607:
594:
589:
588:
569:
529:
493:
442:
441:
422:
421:
402:
401:
380:
358:
329:
289:
286:
283:
280:
279:
257:
250:
230:
201:on Knowledge's
198:
121:
116:
115:
114:
91:
61:
12:
11:
5:
1077:
1075:
1067:
1066:
1061:
1051:
1050:
1036:139.147.60.173
1024:
1021:
1020:
1019:
988:
985:
974:129.11.253.117
961:
941:
938:
918:
915:
910:
906:
902:
897:
893:
889:
884:
880:
876:
873:
868:
864:
860:
855:
851:
847:
842:
838:
834:
831:
828:
825:
822:
802:
799:
794:
790:
784:
780:
776:
771:
767:
761:
757:
753:
750:
730:
727:
722:
718:
697:
694:
689:
685:
679:
675:
671:
666:
662:
656:
652:
648:
645:
625:
622:
619:
614:
610:
606:
601:
597:
586:
568:
565:
564:
563:
548:
528:
525:
524:
523:
497:67.100.217.179
492:
489:
488:
487:
449:
429:
409:
377:
376:
357:
356:what's a path?
354:
353:
352:
328:
327:Multiplication
325:
322:
321:
318:
317:
314:
313:
302:
296:
295:
293:
276:the discussion
263:
262:
246:
234:
233:
225:
213:
212:
206:
195:
181:
180:
118:
117:
113:
112:
107:
102:
93:
92:
90:
89:
82:
77:
68:
62:
60:
59:
48:
39:
38:
35:
34:
28:
13:
10:
9:
6:
4:
3:
2:
1076:
1065:
1062:
1060:
1057:
1056:
1054:
1047:
1045:
1041:
1037:
1033:
1022:
1018:
1014:
1010:
1006:
1005:
1004:
1003:
999:
995:
986:
984:
983:
979:
975:
959:
939:
936:
916:
913:
908:
904:
895:
891:
887:
882:
878:
871:
866:
862:
853:
849:
845:
840:
836:
829:
826:
823:
820:
800:
797:
792:
788:
782:
778:
774:
769:
765:
759:
755:
751:
748:
728:
725:
720:
716:
695:
692:
687:
683:
677:
673:
669:
664:
660:
654:
650:
646:
643:
623:
620:
617:
612:
608:
604:
599:
595:
584:
583:
579:
575:
566:
562:
558:
554:
549:
545:
544:
543:
542:
538:
534:
526:
522:
518:
514:
509:
508:
507:
506:
502:
498:
490:
486:
482:
478:
474:
473:
472:
471:
467:
463:
427:
398:
396:
392:
388:
384:
375:
371:
367:
363:
362:
361:
351:
348:
344:
343:
342:
341:
338:
333:
326:
311:
307:
301:
298:
297:
294:
277:
273:
269:
268:
260:
254:
249:
247:
244:
240:
239:
235:
229:
226:
223:
219:
214:
210:
204:
196:
192:
187:
186:
177:
173:
170:
167:
163:
159:
155:
152:
149:
146:
143:
140:
137:
134:
131:
127:
124:
123:Find sources:
120:
119:
111:
110:Verifiability
108:
106:
103:
101:
98:
97:
96:
87:
83:
81:
78:
76:
72:
69:
67:
64:
63:
57:
53:
52:Learn to edit
49:
46:
41:
40:
37:
36:
32:
26:
22:
18:
17:
1030:— Preceding
1026:
990:
585:
570:
530:
527:unit element
494:
399:
387:163.1.246.64
381:— Preceding
378:
359:
334:
330:
306:Low-priority
305:
265:
231:Low‑priority
209:WikiProjects
171:
165:
157:
150:
144:
138:
132:
122:
94:
19:This is the
1007:Now fixed.
553:JackSchmidt
513:JackSchmidt
477:JackSchmidt
366:JackSchmidt
281:Mathematics
272:mathematics
228:Mathematics
199:Start-class
148:free images
31:not a forum
1053:Categories
574:Wohingenau
88:if needed
71:Be polite
21:talk page
1032:unsigned
533:Charleyc
383:unsigned
337:Gleuschk
56:get help
29:This is
27:article.
460:also?
347:Saibot2
308:on the
154:WP refs
142:scholar
741:so if
708:where
462:Mbw314
205:scale.
126:Google
1009:linas
813:then
169:JSTOR
130:books
84:Seek
1040:talk
1013:talk
998:talk
978:talk
578:talk
557:talk
537:talk
517:talk
501:talk
481:talk
466:talk
391:talk
370:talk
162:FENS
136:news
73:and
300:Low
176:TWL
1055::
1042:)
1015:)
1000:)
980:)
917:…
801:…
726:∈
696:…
621:…
580:)
559:)
547:0.
539:)
519:)
503:)
483:)
468:)
448:Γ
408:Γ
393:)
372:)
156:)
54:;
1038:(
1011:(
996:(
976:(
960:Q
940:Q
937:k
914:+
909:2
905:p
901:)
896:2
892:b
888:+
883:2
879:a
875:(
872:+
867:1
863:p
859:)
854:1
850:b
846:+
841:1
837:a
833:(
830:=
827:y
824:+
821:x
798:+
793:2
789:p
783:2
779:b
775:+
770:1
766:p
760:1
756:b
752:=
749:y
729:k
721:i
717:a
693:+
688:2
684:p
678:2
674:a
670:+
665:1
661:p
655:1
651:a
647:=
644:x
624:,
618:,
613:2
609:p
605:,
600:1
596:p
576:(
555:(
535:(
515:(
499:(
479:(
464:(
428:Q
389:(
368:(
312:.
211::
172:·
166:·
158:·
151:·
145:·
139:·
133:·
128:(
58:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.