  The widely used Double-Exchange model for manganites is shown to support
various "striped" phases at filling fractions 1/n (n=3, 4, 5...), in the
previously unexplored regime of narrow bandwidth and small Jahn-Teller
coupling. Working in two dimensions, our main result is that these stripes can
be individually spin flipped without a physically relevant change in the
energy, i.e., we find a large groundstate manifold with nearly degenerate
energies. The two-dimensional spin system thus displays an unexpected
dynamically generated dimensional reduction into decoupled one-dimensional
stripes, even though the electronic states remain two-dimensional. Relations of
our results with recent literature addressing compass models in quantum
computing are discussed.
