Bounded Model Theory and its Applications to Bounded Arithmetic

Bounded model theory can be considered as part of first-order model theory, which its aim is to study model-theoretic notions in a language consisting of an order relation where all quantifiers are restricted to the bounded ones. One can apply bounded model theory to study some problems in bounded arithmetic. Bounded arithmetic can be considered as a sub-theory of first-order Peano arithmetic in an extended language. Bounded arithmetic has some applications in computational complexity theory. There are already some related bounded model-theoretic concepts like bounded quantifier elimination and bounded model completeness which has been applied to bounded arithmetic and complexity theory. In this article, we review some known results and prove some new ones in bounded model theory and use them to obtain certain results in bounded arithmetic and complexity theory. In particular, we define the notion of bounded model companion and study its relations to some fundamental problems in complexity theory.