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

Understand

There are 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 non-stationary situation in quantum field theory.
• Furthermore there are secular effects in the n-point correlation functions for low enough mass.