Characters of different secular effects in various patches of de Sitter space

There arc at least three different types of secular effects in the two-point correlation functions in scalar quantum field theories in de Sitter space-time. The first one is specific to de Sitter massless and tachyonic minimally coupled scalar fields. The remaining two are generic and are encountered practically in any nonstationary situation in quantum field theory. Furthermore there are secular effects in the n-point correlation functions for low enough mass. They arc also specific to de Sitter quantum field theory. In this paper we focus on the differences between the secular effects in two-point functions. We discuss also their character in different patches of de Sitter space-time-global, expanding and contracting Poincare patches.