D. Osadchy, J. E. Avron
Hofstadter butterfly as Quantum phase diagram
(1824K, Latex 2.09 with 1 EPS color figure, (Revtex package is used))

ABSTRACT.  The Hofstadter butterfly is viewed as a quantum phase diagram 
with infinitely many phases, labeled by their (integer) Hall 
conductance, and a fractal structure. We describe various 
properties of this phase diagram: We establish Gibbs phase rules; 
count the number of components of each phase, and characterize the 
set of multiple phase coexistence.