Hitting time of Brownian Motion on a line

445 Views Asked by At

Given a 3-dimensional Brownian motion $B_t$, we know that it is transient. But how can we show that if it starts outside a straight line, it will remain outside forever with probability $1$ ? Any ideas?

1

There are 1 best solutions below

3
On BEST ANSWER

The orthogonal projection of $B_t$ on a plane normal to the line is $2$-dimensional Brownian motion, which with probability $1$ will never hit the origin.