SCIENCE AT THE EDGE SEMINAR Friday, 28 January 2011 at 11:30am Room 1400 Biomedical and Physical Sciences Bldg. Refreshments at 11:15 Speaker: Bruno Nachtergaele Department of Mathematics, University of California at Davis Title: Gapped Phases of Quantum Spin Systems (towards a qualitative theory of gapped ground states) Abstract: Quantum spin Hamiltonians have been used to model a broad variety of phenomena in condensed matter physics since the early years of quantum theory. More recently, they have been employed in the theory of quantum information and computation. Much of what we know about the ground states of quantum spin Hamiltonians is derived from the exact solutions that can be found for a relatively small number of models. It is essential, however, that we develop our understanding of the generic behaviors of this class of models. In this talk I will review recent work aimed at a qualitative theory of gapped ground state phases of quantum spin systems in one and more dimensions. Quantum spin models have a long history of inspiring new mathematics going back at least eighty years. I will argue that in our quest to understand quantum spin models more fully, we will once again be led to new mathematical discoveries.