PATH-INTEGRALS AND INSTANTONS IN QUANTUM-GRAVITY - MINISUPERSPACE MODELS

While there does not at this time exist a complete canonical theory of full 3+1 quantum gravity, there does appear to be a satisfactory cano nical quantization of minisuperspace models. The method requires no '' choice of time variable'' and preserves the systems' explicit reparame trization invariance. In the following study, this canonical formalism is used to derive a path integral for quantum minisuperspace models. As it comes from a well-defined canonical starting point, the measure and contours of integration are specified by this construction. The pr operties of the resulting path integral are analyzed, both exactly and in the semiclassical limit. Particular attention is paid to the role of the (unbounded) Euclidean action and Euclidean instantons are argue d to contribute as e(-\SE\/HBAR).