Welcome to European Tribune. It's gone a bit quiet around here these days, but it's still going.
I've had that sig on other scoop sites, before they had picture embedding macros, and I've kept it for sentimental reasons :)

It's a piece of LaTeX which represents the defining property of a martingale.

The simplest example of a martingale in this sense is a double or nothing gambling strategy in certain games of chance(*), but a better way of understanding them is that they are purely random processes, which cannot be predicted based on historical observations: if you try to predict their future, your best guess is to duplicate the present, regardless of what you've seen in the past.

(*)wherein one proves that double or nothing fails to help one win: when the strategy has no statistical trend, then there is no advantage from using it.

$E(X_t|F_s) = X_s,\quad t > s$

by martingale on Sun Aug 17th, 2008 at 03:44:38 AM EST
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