Abstract

The core of this article is a general theorem with a large number of specializations. Given a
manifold $N$ and a finite number of one-parameter groups of point transformations on $N$ with
generators $Y, X_{(1)}, \cdots, X_{(d)} $, we obtain, via
functional integration over spaces of pointed paths on $N$ (paths with one fixed point), a
one-parameter group of functional operators acting on tensor or spinor fields on $N$. The
generator of this group is a quadratic form in the Lie derivatives $\La_{X_{(\a)}}$ in the 
$X_{(\a)}$-direction plus a term linear in $\La_Y$. 

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The basic functional integral is over $L^{2,1}$ paths $x: {\bf T} \ra N$ (continuous paths
with square integrable first derivative). Although the integrator is invariant under time
translation, the integral is powerful enough to be used for systems which are not time
translation invariant. We give seven non trivial applications of the basic formula, and we
compute its semiclassical expansion.

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The methods of proof are rigorous and combine Albeverio H\o egh-Krohn oscillatory integrals
with Elworthy's parametrization of paths in a curved space. Unlike other approaches we solve
 Schr\"odinger type equations directly, rather than solving first diffusion equations
and then using analytic continuation.