Quantum torus chain

We introduce a set of one-dimensional quantum lattice models which we refer to as the quantum torus chain. These models have discrete global symmetry and projective on-site representations. They possess an integer-valued parameter which controls the presence or absence of frustration. Depending on whether this parameter is even or odd, these models exhibit either gapped symmetry-breaking phases with isolated critical points or gapped symmetry-breaking phases separated by gapless phases. We discuss the property of these phases and phase transitions for two special values of the parameter and point out many open problems.