  Essential to understanding the cuprate pseudogap phase is a study of the
charge (and spin) response functions, which we address here via a consistent
approach to the Fermi arcs and the Fermi pockets scenario of Yang, Rice and
Zhang (YRZ). The two schemes are demonstrated to be formally similar, and to
share a common physics platform; we use this consolidation to address the
inclusion of vertex corrections which have been omitted in YRZ applications. We
show vertex corrections can be easily implemented in a fashion analytically
consistent with sum rules and that they yield important contributions to most
observables. A study of the charge ordering susceptibility of the YRZ scenario
makes their simple physics evident: they represent the inclusion of charged
bosonic, spin singlet degrees of freedom, and are found to lead to a double
peak structure.
