Dividing chains have been used as conditions to isolate adequate subclasses of simple theories. In the first part of this
paper we present an introduction to the area. We give an overview on fundamental notions and present proofs of some of the
basic and well-known facts related to dividing chains in simple theories. In the second part we discuss various characterizations
of the subclass of low theories. Our main theorem generalizes and slightly extends a well-known fact about the connection
between dividing chains and Morley sequences (in our case: independent sequences). Moreover, we are able to give a proof that
is shorter than the original one. This result motivates us to introduce a special property of formulas concerning independent
dividing chains: For any dividing chain there exists an independent dividing chain of the same length. We study this property
in the context of low, short and
ω -categorical simple theories, outline some examples and define subclasses of low and short theories, which imply this property.
The results give rise to further studies of the relationships between some subclasses of simple theories.
Key words or phrases Simple theories - Dividing chains - Morley sequences
Research supported by CNPq grant 150309/2003-1.
Research supported by CNPq grant 304365/2003-3 (Modelos, Provas e Algoritmos)