| The thesis studies the character (PA) of Sacts and describes some special monoids with the condition (PA), and introduces the concepts of YJ-injectivity acts and GP-injectivity acts, and describes some special monoids with these concepts.In section 2, we study further the condition (PA), and give a necessary and sufficient condition that a cyclic act satisfies the condition (PA).In section 3, we describe the left elimination monoids with the condition (PA), and get a characterization of S~acts on some special right PSF monoids.In section 4 , we introduce the concepts of YJ-injectivity acts and GP-injectivity acts, and get a characterization of YJ-injectivity acts , and describe the -n -regular monoids with the concepts of GP-injectivity acts. |
