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Recall that a module is called

  1. semisimple if every submodule is a direct summand

  2. pure semisimple if every pure submodule is a direct summand

There is quite a bit of work on semisimple and pure semisimple modules, of course.

My question is

What is a module called if every submodule is pure?

and

What is known about these modules and where can I read about them?

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2 Answers 2

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Hmmm, I seem to have found the answer to this question. In

Regular and semisimple modules

by Cheatham and Smith in 1976, they call a module regular if every submodule is pure. Regular is of course an overused word, and maybe other people have called this different things. But the justification makes some sense: if I is a 2-sided ideal of R, then R/I is a regular R-module if and only if R/I is a von Neumann regular ring.

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If R is a discrete valuation ring and M is an R-module such that the annihilator of M isn't zero , then every pure submodule of M is a direct summand. You can see some results about the question in the book "Modules over Discrete Valuation Rings" by Krylov and Tuganbaev.

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