This book presents further developments and applications in the area of completely regular semigroup theory, beginning with applications of Polák's theorem to obtain detailed descriptions of various kernel classes including the K-class covers of the kernel class of all bands. The important property of modularity of the lattice of varieties of completely regular semigroups is then employed to analyse various principal sublattices. This is followed by a study of certain important complete congruences on the lattice; the group, local and core relations. The next chapter is devoted to a further treatment of certain free objects and related word problems. There are many constructions in the theory of semigroups. Those that have played an important role in the theory of varieties of completely regular semigroups are presented as they apply in this context. The mapping that takes each variety to its intersection with the variety of bands is a complete retraction of the lattice of varieties of completely regular semigroups onto the lattice of band varieties and so induces a complete congruence for which every class has a greatest member. The sublattice generated by these greatest members is then investigated with the help of many applications of Polák's theorem. The book closes with a fascinating conjecture regarding the structure of this sublattice.
"Current advancements with their insights, related recent results and their methodologies etc. are nicely and elaborately included in this book and some of which are enlighted with in-depth understanding and special mention of the whole lattice of varieties of completely regular as a subdirect product of lattices which is in fact a remarkable theorem due to Pola'k. The book consists of an insightful and resourceful bibliography at the end." (Sanjib Kumar Datta, zbMATH 1545.20001, 2024)
This review treats the two volumes as a single whole. One of the outstanding features consists of the Introduction and Review contained within each chapter and I can think of no better way to outline them than by quoting liberally from this material. The first author passed away before the publication of these two volumes. He will be greatly missed. (Peter R. Jones, Semigroup Forum, Vol. 111 (1), 2025)
Current advancements with their insights, related recent results and their methodologies etc. are nicely and elaborately included in this book and some of which are enlighted with in-depth understanding and special mention of the whole lattice of varieties of completely regular as a subdirect product of lattices which is in fact a remarkable theorem due to Pola k. The book consists of an insightful and resourceful bibliography at the end. (Sanjib Kumar Datta, zbMATH 1545.20001, 2024)
Current advancements with their insights, related recent results and their methodologies etc. are nicely and elaborately included in this book and some of which are enlighted with in-depth understanding and special mention of the whole lattice of varieties of completely regular as a subdirect product of lattices which is in fact a remarkable theorem due to Pola k. The book consists of an insightful and resourceful bibliography at the end. (Sanjib Kumar Datta, zbMATH 1545.20001, 2024)







