  It has been proposed recently by some of the authors that the quantum phase
transition of a topological insulator like the SSH model may be detected by the
eigenvalues and eigenvectors of the reduced density matrix. Here we further
extend the scheme of identifying the order parameters by considering the SSH
model with the addition of triplet superconductivity. This model has a rich
phase diagram due to the competition of the SSH "order" and the Kitaev "order",
which requires the introduction of four order parameters to describe the
various topological phases. We show how these order parameters can be expressed
simply as averages of projection operators on the ground state at certain
points deep in each phase and how one can simply obtain the phase boundaries. A
scaling analysis in the vicinity of the transition lines is consistent with the
quantum Ising universality class.
