  We use determinant Quantum Monte Carlo (DQMC), in combination with the
principal component analysis (PCA) approach to unsupervised learning, to
extract information about phase transitions in several of the most fundamental
Hamiltonians describing strongly correlated materials. We first explore the
zero temperature antiferromagnet to singlet transition in the Periodic Anderson
Model, the Mott insulating transition in the Hubbard model on a honeycomb
lattice, and the magnetic transition in the 1/6-filled Lieb lattice. We then
discuss the prospects for learning finite temperature superconducting
transitions in the attractive Hubbard model, for which there is no sign
problem. Finally, we investigate finite temperature charge density wave (CDW)
transitions in the Holstein model, where the electrons are coupled to phonon
degrees of freedom, and carry out a finite size scaling analysis to determine
$T_c$. We examine the different behaviors associated with Hubbard-Stratonovich
auxiliary field configurations on both the entire space-time lattice and on a
single imaginary time slice, or other quantities, such as equal-time Green's
and pair-pair correlation functions.
