We provide here the first steps toward a Classification Theory of Elementary Classes with no maximal models, plus some mild set theoretical assumptions, when the class is categori...
A study is carried out of the elementary theory of quotients of symmetric groups in a similar spirit to [10]. Apart from the trivial and alternating subgroups, the normal subgroup...
Coalgebra develops a general theory of transition systems, parametric in a functor T; the functor T specifies the possible one-step behaviors of the system. A fundamental question...
The present paper investigates the groups of automorphisms for some lattices of modal logics. The main results are the following. The lattice of normal extensions of S4.3, NExt S4....
We describe a new way to construct large subdirectly irreducibles within an equational class of algebras. We use this construction to show that there are forbidden geometries of m...
We give a sound and complete propositional S5 tableau system of a particularly simple sort, having an easy completeness proof. It sheds light on why the satisfiability problem for...
This article surveys R. Parikh's work on feasibility, bounded arithmetic and the complexity of proofs. We discuss in depth two of Parikh's papers on these subjects and s...