A model for reducing the angulon operator
  We propose a mathematical model for the recently introduced angulon. In our formulation, the angulon operator is decomposable relative to the field of Hilbert spaces over the probability measure space. That is, we transfer the population of phonons from the inner structure of the many-body Hamiltonian to the definition of the measure. We do not compute the measure itself. However, we demonstrate that the approach allows us to perform angular reduction thereby considerably simplifying the spectral analysis. 
Rytis Jursenas and Mikhail Lemeshko
math-ph cond-mat.quant-gas math.MP quant-ph