TRANSITION BETWEEN QUANTUM COHERENCE AND INCOHERENCE

We show that a transformed Caldeira-Leggett Hamiltonian has two distin ct families of fixed points rather than a single unique fixed point as often conjectured based on its connection to the anisotropic Kondo mo del. The two families are distinguished by a sharp qualitative differe nce in their quantum coherence properties and we argue that this disti nction is best understood as the result of a transition in the model b etween degeneracy and nondegeneracy in the spectral function of the '' spin-flip'' operator.