M. Cranston et al., THE RADIAL PART OF BROWNIAN-MOTION .2. ITS LIFE AND TIMES ON THE CUT LOCUS, Probability theory and related fields, 96(3), 1993, pp. 353-368
This paper is a sequel to Kendall (1987), which explained how the Ito
formula for the radial part of Brownian motion X on a Riemannian manif
old can be extended to hold for all time including those times at whic
h X visits the cut locus. This extension consists of the subtraction o
f a correction term, a continuous predictable non-decreasing process L
which changes only when X visits the cut locus. In this paper we deri
ve a representation of L in terms of measures of local time of X on th
e cut locus. In analytic terms we compute an expression for the singul
ar part of the Laplacian of the Riemannian distance function. The work
uses a relationship of the Riemannian distance function to convexity,
first described by Wu (1979) and applied to radial parts of GAMMA-mar
tingales in Kendall (1993).