Time inversion of Brownian motion (source code)

= Time inversion of Brownian motion

If $W$ is <Brownian motion>, then
$$
B_0=0,
\qquad B_t=tW_{1/t}\quad(t>0)
$$
is also Brownian motion. Its covariance is $\min(s,t)$, and continuity at zero follows from $W_u/u\to0$ almost surely.