  We first prove the L^p-convergence (p\geq 1) and a Fernique-type exponential
integrability of divergence functionals for all Cameron-Martin vector fields
with respect to the pinned Wiener measure on loop spaces over a compact
  Riemannian manifold. We then prove that the Driver flow is a smooth transform
on path spaces in the sense of the Malliavin calculus and has an
\infty-quasi-continuous modification which can be quasi-surely well defined on
path spaces. This leads us to construct the Driver flow on loop spaces through
the corresponding flow on path spaces. Combining these two results with the
Cruzeiro lemma
  [J. Funct. Anal. 54 (1983) 206-227] we give an alternative proof of the
quasi-invariance of the pinned Wiener measure under Driver's flow on loop
spaces which was established earlier by Driver [Trans. Amer. Math. Soc.
  342 (1994) 375-394] and Enchev and Stroock [Adv. Math. 119 (1996) 127-154] by
Doob's h-processes approach together with the short time estimates of the
gradient and the Hessian of the logarithmic heat kernel on compact
  Riemannian manifolds. We also establish the L^p-convergence (p\geq 1) and a
Fernique-type exponential integrability theorem for the stochastic
anti-development of pinned Brownian motions on compact Riemannian manifold with
an explicit exponential exponent. Our results generalize and sharpen some
earlier results due to Gross [J. Funct. Anal. 102 (1991) 268-313] and Hsu
[Math. Ann. 309
  (1997) 331-339]. Our method does not need any heat kernel estimate and is
based on quasi-sure analysis and Sobolev estimates on path spaces.

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