SPA Colloquium: Sal Pace (MIT/Princeton IAS)

Title:  When symmetry does the unexpected

Abstract: Symmetry is one of the central organizing principles of theoretical physics. It gives conservation laws, explains degeneracies, and characterizes many phases of matter through spontaneous symmetry breaking. In quantum systems, symmetry can do something even more surprising: it can enforce nontrivial entanglement and forbid an apparently ordinary, featureless phase from existing at all. In this colloquium, starting from the Lieb–Schultz–Mattis theorem and the modern notation of ’t Hooft anomalies, we will survey this unexpected power of symmetry and its consequences for quantum phases of matter and quantum field theory.