| Popis: |
In this thesis, we study the problem of the existence of test modules for the projectivity. A right R-module is said to be a test module if it holds for every right R-module M that M is projective whenever T ∈ M⊥ . We show that test modules exist over right perfect rings, although their existence is not provable in ZFC in case of non-right perfect rings. In order to prove this, we use Shelah's uni- formization principle, which is independent of the axioms of ZFC. Furthermore, we show that test modules exist over rings of finite global dimension assuming the weak diamond principle, which is also independent of ZFC. 1 |
