Math 2.0

K-theory K0 and projective modules Concept

Stably free module

Summary

A module is stably free if it becomes free after adding a free module of finite rank. Every free module of finite rank is stably free, but the converse fails in general. A finitely generated projective module is stably free exactly when its class in reduced K0K_0 is zero. So K0K_0 cannot tell a stably free module from a free one. The question of when stably free modules are free is a central theme of the theory of projective modules.

Further reading

  1. Web https://en.wikipedia.org/wiki/Stably_free_module
About this page
TagYMXJ4JTQPF
URIm2://YMXJ4JTQPF
Kindconcept
WritingW0 stub
MSC19A13, 13C10
SpecializesFinitely generated projective module
Same as
Changed3 November 2026

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