Exact correlation functions in the cuprate pseudogap phase: combined   effects of charge order and pairing
  There is a multiplicity of charge ordered, pairing-based or pair density wave theories of the cuprate pseudogap, albeit arising from different microscopic mechanisms. For mean field schemes (of which there are many) we demonstrate here that they have precise implications for two body physics in the same way that they are able to address the one body physics of photoemission spectroscopy. This follows because the full vertex can be obtained exactly from the Ward-Takahashi identity. As an illustration, we present the spin response functions, finding that a recently proposed pair density wave (Amperean pairing) scheme is readily distinguishable from other related scenarios. 
Rufus Boyack, Chien-Te Wu, Peter Scherpelz, K. Levin
cond-mat.supr-con cond-mat.str-el