We develop the theory of coregular sequences and codepth for modules that need not be finitely generated or artinian over a Noetherian ring. use this to give new version theorem Hellus characterizing set-theoretic complete intersections in terms local cohomology modules. also define quasi-cyclic as increasing unions cyclic modules, show at least two are quasi-cyclic. then focus our attention on...

A class of decision problems is Boolean if it is closed under the set–theoretic operations of union, intersection and complementation. The paper introduces new Boolean classes of decision problems based on algebraic constraints imposed on transitions of finite automata. We discuss issues related to specifications of these classes from algebraic, computational and proof–theoretic points of view.

Every lattice is isomorphic to a lattice whose elements are sets of sets and whose operations are intersection and the operation ∨∗ defined by A ∨∗ B = A ∪ B ∪ {Z : (∃X ∈ A)(∃Y ∈ B)X ∩ Y ⊆ Z}. This representation spells out precisely Birkhoff’s and Frink’s representation of arbitrary lattices, which is related to Stone’s set-theoretic representation of distributive lattices. (AMS Subject Classi...