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In my classes on stochastic processes we often refer to $\sigma$-Algebras as information or as the history or future of some process $X$.

E.g.

$$ \mathcal{F}^{X}_{[0, t]} = \sigma(X_s , 0 \leq s \leq t)$$

we described as the history up to point $t \in T$ where $T \subset [0, \infty)$.

Generally speaking I understand that a $\sigma$-Algebra is a set of sets with specific properties (like being closed under countable unions etc) and that an element of a $\sigma$-Algebra is interpreted as an event that can occur when conducting a random experiment.

What I don't understand is how we can regard this as information or history since the $\sigma$-Algebra doesn't say what happens or happened but only which events could occur or could have occurred. After all, for every event $A$ in the $\sigma$-Algebra the complement $A^C$ is also contained.

lpnorm
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  • The interpretation of sigma algebras as information mostly makes sense when conditioning on a sigma algebra – Dasherman Sep 06 '21 at 11:16
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    https://math.stackexchange.com/questions/3131221/what-is-meant-by-a-filtration-contains-the-information-until-time-t?rq=1 –  Sep 06 '21 at 11:54

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