  The ground state of 2D electrons in high magnetic field is studied by the
density matrix renormalization group method. The ground state energy,
excitation gap, and pair correlation functions are systematically calculated at
various fillings in the lowest and the second lowest Landau levels. The ground
state phase diagram, which consists of incompressible liquid state,
compressible liquid state, stripe state, pairing state, and Wigner crystal is
determined.
