FAKE INSTABILITY IN THE EUCLIDEAN FORMALISM OF QUANTUM TUNNELING

The Euclidean path-integral formalism is studied for the system withou t any unstable state. While the usual bounce calculation yields a fake complex energy spectrum, proper account of the global structure of th e functional space is shown to lead to the real eigenvalues. For this purpose, the valley instanton is constructed by the proper valley meth od and the dilute-gas approximation is carried out. This establishes a general imaginary-time formalism, unifying the instanton and the boun ce method.