The inverse limit of a family of -modules is the dual notion of a direct limit and is characterized by the following mapping property. For a directed set and a family of -modules , let be an inverse system. is some -module with some homomorphisms , where for each ,
(1)
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such that if there exists some -module with homomorphisms , where for each ,
(2)
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then a unique homomorphism is induced and the above diagram commutes.
The inverse limit can be constructed as follows. For a given inverse system, , write
(3)
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