Band hybridization in rotational motion

The back-bending behaviour of the moment of inertia as a function of the square of the angular velocity, for the ground-, and ß-rotational trajectories in ₆₆¹⁵⁶Dy₉₀, is described in terms of band hybridization.     

On a global analytic Positivstellensatz

We consider several modified versions of the Positivstellensatz for global analytic functions that involve infinite sums of squares and/or positive semidefinite analytic functions. We obtain a general local-global criterion which localizes the obstruction to have such a global result. This criterion allows us to get completely satisfactory results for analytic curves, normal analytic surfaces and real coherent analytic sets whose connected components are all compact.