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Jun 5, 2013 at 10:05 history edited Davide Giraudo CC BY-SA 3.0
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Jun 4, 2013 at 12:34 comment added Matthias Ludewig Yes, sorry, I think I overread the $\mathbb{N}$ in the exponent.
Jun 4, 2013 at 12:33 vote accept Matthias Ludewig
Jun 4, 2013 at 8:21 comment added Davide Giraudo I probably missed something, but here $B$ is a Borel subset of the space of sequences of elements of $\BBb R^n$. And if $(x_j)_j$, $(y_j)_j$ are two sequences, and $B_1$, $B_2$ two such Borel sets, define $z=(x_1,y_1,x_2,\dots,)$, and we can write $S((x_j)_j,B_1)\cup S((y_j)_j,B_2)=\{f,(f(z_{2n+1})\in B_1\mbox{ or }f(z_{2n})\in B_2\}$. For countable unions, we can proceed similarly taking a bijection from $\Bbb N^2$ to $\Bbb N$.
Jun 4, 2013 at 8:18 history undeleted Davide Giraudo
Jun 4, 2013 at 8:12 history deleted Davide Giraudo
Jun 4, 2013 at 6:23 comment added Matthias Ludewig Also, the union of two such sets is generally not of this form anymore.
Jun 4, 2013 at 6:21 comment added Matthias Ludewig This seems false. You at least need to allow different sets $B$ for each $x_j$, otherwise the Sigma-Algebra is too small.
Jun 3, 2013 at 23:13 history answered Davide Giraudo CC BY-SA 3.0