angle brackets notation statistics

Question

I am working on a project that involves brownian motion. What does the notation $<r_{ij}(0)r_{ij}(\tau)>$ mean if $r_{ij}(t)$ is the separation distance between particle $i$ and $j$ at time $t$?

Its some sort of average I'm guessing but of what and how do you calculate?

Thanks

Answer 1

Can you give a bit more information? Is this a two-object Brownian motion? I am trying to understand what it means and the context.

Offhand it looks like an inner product, of course. But that is just a guess based on the form.