  We address quantum oscillation experiments in high Tc superconductors and the
evidence from these experiments for a pseudogap versus a Fermi liquid phase at
high magnetic fields. As a concrete alternative to a Fermi liquid phase, the
pseudogap state we consider derives from earlier work within a Gor'kov-based
Landau level approach. Here the normal state pairing gap in the presence of
high fields is spatially non-uniform, incorporating small gap values. These, in
addition to d-wave gap nodes, are responsible for the persistence of quantum
oscillations. Important here are methodologies for distinguishing different
scenarios. To this end we examine the temperature dependence of the
oscillations. Detailed quantitative analysis of this temperature dependence
demonstrates that a high field pseudogap state in the cuprates may well
"masquerade" as a Fermi liquid.
