This paper is an investigation of
conditions on a module A under which the natural map
is an injection. The investigation leads to a theorem that a commutative von
Neumann regular ring is self-injective if and only if the natural map
is an injection for all collections {Fα} and {Gβ} of free modules. An example is
constructed of a commutative ring R for which the natural map
is not an injection.
|