Joye A., Pfister Ch-Ed.
Non-Abelian Geometrical Effect in Quantum Adiabatic Transitions
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ABSTRACT.  We establish a new formula for the probability of a quantum 
adiabatic transition between two 
permanently degenerated energy-levels which do not cross. This formula 
corresponds to the non-abelian generalization of the Landau-Dykhne formula 
valid for the non-degenerate case. It applies in particular in cases of
symmetry induced degeneracy, a typical example being the Kramer's 
degeneracy.