Solution (source code)

= Solution

A process $(W_t)_{t\geq0}$ is a standard <Brownian motion> if:

* $W_0=0$ almost surely;
* its sample paths are almost surely continuous;
* it has independent increments; and
* for $0\leq s<t$,
  $$
  W_t-W_s\sim N(0,t-s).
  $$

Equivalently, every future increment is independent of the past filtration and has the stated centred normal law.