%0 Journal Article %T Quantum phase transitions in antiferromagnets and superfluids %A Subir Sachdev %A Matthias Vojta %J Physics %D 1999 %I arXiv %R 10.1016/S0921-4526(99)01726-3 %X We present a general introduction to the non-zero temperature dynamic and transport properties of low-dimensional systems near a quantum phase transition. Basic results are reviewed in the context of experiments on the spin-ladder compounds, insulating two-dimensional antiferromagnets, and double-layer quantum Hall systems. Recent large N computations on an extended t-J model (cond-mat/9906104) motivate a global scenario of the quantum phases and transitions in the high temperature superconductors, and connections are made to numerous experiments. %U http://arxiv.org/abs/cond-mat/9908008v1