On degenerations and extensions of finite dimensional modules
The paper deals with a geometric study of finite dimensional modules over a finite dimensional associative algebra. The author proves a cancellation theorem for degenerations of modules and considers its applications to the theory of preprojective modules and modules over tame concealed algebras, the theory of matrix pencils and others. In fact, the main results of the article under review have been improved and generalized in two papers written later but published earlier [\textit{K. Bongartz}, Comment. Math. Helv. 69, No. 4, 575-611 (1994; Zbl 0832.16008) and Ann. Sci. Éc. Norm. Supér., IV. Sér. 28, No. 5, 647-668 (1995; Zbl 0844.16007)].
scientific article; zbMATH DE number 934300