Locality of DS and associated varieties
Journal of Pure and Applied Algebra
We prove that the pseudovariety DS, of all finite monoids, each of whose regular D" role="presentation" style="box-sizing: border-box; margin: 0px; padding: 0px; display: inline-block; font-style: normal; font-weight: normal; line-height: normal; font-size: 14.4px; text-indent: 0px; text-align: left; text-transform: none; letter-spacing: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;">D-classes is a subsemigroup, is local. (A pseudovariety (or variety) V is local if any category whose local monoids belong to V divides a member of V.) The proof uses the “kernel theorem” of the first author and Pustejovsky together with the description by Weil of DS as an iterated “block product”.
The one-sided analogues of these methods provide wide new classes of local pseudovarieties of completely regular monoids. We conclude, however, with the second author's example of a variety (and a pseudovariety) of completely regular monoids that is not local.
Jones, Peter R. and Trotter, Peter G., "Locality of DS and associated varieties" (1995). Mathematics, Statistics and Computer Science Faculty Research and Publications. 606.