Generically $\tau$-regular irreducible components of module varieties

Abstract

In the representation theory of finite-dimensional algebras, the study of projective presentations of maximal rank is closely related to the study of generically $\tau$-regular irreducible components of varieties of modules over such algebras. We show that a module is $\tau$-regular if and only if its minimal projective presentation is of maximal rank. This is a refinement of a theorem by Plamondon. We prove that generic extensions of generically $\tau$-regular components by simple projective modules are again generically $\tau$-regular. This leads to the classification of all generically $\tau$-regular components for triangular algebras. We also show that an algebra is hereditary if and only if all irreducible components of its varieties of modules are generically $\tau$-regular. Finally, we discuss when the set of generically $\tau$-regular components coincides with the set of generically $\tau^-$-regular components.