Operator-algebraic approach to the yrast spectrum of weakly interacting trapped bosons

We present an operator-algebraic approach to derive the low-lying quasidegenerate spectrum of weakly interacting trapped N bosons with total angular momentum L for the case of L/N1. We demonstrate that the lowest-lying excitation spectrum is given by 27gn₃(n₃-1)/34, where g is the strength of the repulsive contact interaction and n₃ is the number of excited octupole quanta. Our method provides constraints for these quasidegenerate many-body states and gives higher excitation energies that depend linearly on N.