General Physics Colloquium Wednesday 12 October at 15.15 in Fys. Aud. Speaker: Nathan Harshman American University / IFA Title: Five is Different: Symmetry, Solvability and Entanglement in Quantum Few-Body Systems Abstract: In quantum mechanics, one particle systems are "easy" to solve, and two particles are (technically) always solvable. Three and four particles are a lot harder, and five particles...fuhgettaboutit. But why? And why should we care? The second question is straightforward: phenomena in particle, nuclear, atomic, molecular, and solid state systems can often be reduced to the dynamics of few-body systems. The increasingly precise measurement and control of ultracold atoms in optical traps allows predictions of few-body quantum theory to be tested as never before. Ultracold atoms could be the working material for new quantum technologies that exploit coherence and entanglement to perform efficient information processing. However, answering the first question "why is few body physics so hard" requires looking at how symmetry becomes less and less constraining as the number of particles increases, and finally completely fails (for most systems) at five particles. Coffee and cake will be served at 15:05