Dominions and closed varieties of bands

Abstract

In this paper, we improve the results of [1] and solve one of the open problems of [1]. First, we have shown that all subvarieties of the variety of rectangular bands are closed in the variety of n-nilpotent extension of bands. Further, we gave the new, simple and shorter proof of closedness of the variety of regular bands and lastly, we have shown that all subvarieties of the variety of normal bands are closed in the variety of left semiregular bands.