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Another Criterion for a Ring to be Projective‐Free
Author(s) -
Cohn P. M.
Publication year - 2005
Publication title -
bulletin of the london mathematical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.396
H-Index - 48
eISSN - 1469-2120
pISSN - 0024-6093
DOI - 10.1112/s0024609305004893
Subject(s) - mathematics , projective test , invariant (physics) , idempotence , pure mathematics , mathematics subject classification , ring (chemistry) , matrix ring , basis (linear algebra) , pencil (optics) , combinatorics , algebra over a field , geometry , chemistry , organic chemistry , mechanical engineering , invertible matrix , engineering , mathematical physics
It is proved that a ring (≠0) is projective‐free precisely when it has invariant basis number and every idempotent matrix not equal to I is non‐full. 2000 Mathematics Subject Classification 16D40.