  We use the microscopic Hartree-Fock approximation to investigate various
quantum phase transitions associated with possible spontaneous symmetry
breaking induced by a tilted magnetic field in the integral quantum Hall regime
of wide parabolic wells and zero width double well (bilayer) systems. We
propose a general class of variational wavefunctions that describe several
types of parity, spin, and translational symmetry breaking, including spin and
charge density wave phases. Zero temperature quantum phase diagrams for these
systems are calculated in the parameter regime of experimental interest. We
discuss the symmetry properties of our predicted quantum phase diagrams and
give a unified picture of these novel many-body phases. A conceptually new
aspect of our theory is the predicted possibility for the spontaneous breaking
of parity symmetry, which indicates a ``ferroelectric'' quantum order in
integer quantum Hall systems and has not been considered in the literature
before.
