Effective Theories of Quantum Phases of Matter

Physical systems look different when observed at different resolutions: what appears as a continuum liquid to the naked eye becomes a cluster of jiggling atoms when observed at the resolution of an electron microscope. Effective field theory provides a description of physics in terms of degrees of freedom appropriate to a given resolution. Over the last couple of decades, physicists have developed effective field theory tools which, to a large extent, unify fields as diverse as atomic and condensed-matter physics, particle and nuclear physics, and cosmology. The ensuing interaction between different branches of physics has never been as fruitful as it is now. Numerous physical phenomena, first predicted and studied in high-energy physics, have found their realization in novel materials. On the other hand, the richness of condensed-matter physics provides a lasting source of inspiration for new developments in high-energy physics and cosmology. Extremely useful in general, the effective field theory tools become indispensable for quantum phases of matter whose low-energy physics is driven by collective excitations, either due to the presence of spontaneous symmetry breaking or due to strong microscopic interactions. The aim of this program is to give a new impulse to a further development of this exciting interdisciplinary field. We bring together leading practitioners working on effective theories of quantum phases of matter across several branches of physics. Our goal is to map out important open problems with broad relevance and look for new directions towards their solution, to reinvigorate existing collaborations and foster new connections.