  We provide a complete theoretical interpretation of the metallic broken
spin/valley symmetry states recently discovered in ABC trilayer graphene (ABC)
perturbed by a large transverse displacement field. Our conclusions combine
insights from ABC trilayer graphene electronic structure models and mean field
theory, and are guided by precise magneto-oscillation Fermi-surface-area
measurements. We conclude that the physics of ABC trilayer graphene is shaped
by the principle of momentum-space condensation, which favors Fermi surface
reconstructions enabled by broken spin/valley flavor symmetries when the
single-particle bands imply thin annular Fermi seas. We find one large outer
Fermi surface enclosed majority-flavor states and one or more small inner
hole-like Fermi surfaces enclosed minority-flavor states that are primarily
responsible for nematic order. The smaller surfaces can rotate along a ring of
van-Hove singularities or reconstruct into multiple Fermi surfaces with little
cost in energy. We propose that the latter property is responsible for the
quantum oscillation frequency fractionalization seen experimentally in some
regions of the carrier-density/displacement-field phase diagram.
