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18 votes
3 answers
1k views

Is there a natural measurable structure on the $\sigma$-algebra of a measurable space?

Let $(X, \Sigma)$ denote a measurable space. Is there a non-trivial $\sigma$-algebra $\Sigma^1$ of subsets of $\Sigma$ so that $(\Sigma, \Sigma^1)$ is also a measurable space? Here is one natural ...
Tom LaGatta's user avatar
  • 8,512
4 votes
2 answers
274 views

Does strong stochastic ordering exist?

For two probability measure $\mu$ and $\nu$ on $\mathbb{R}$, we call $\mu$ is stochastically smaller than $\nu$ (i.e., $\mu\leq\nu$) , if $\int f \, d\mu\leq\int f \, d\nu$ for any nonnegative bounded ...
Jinxiang Yao's user avatar
2 votes
0 answers
78 views

$\sigma$-fields as closure systems

Let $(\Omega,\mathcal A, P)$ be a probability space and let $\Sigma(\mathcal A) \subset 2^{\mathcal A}$ be the collection of all sub-$\sigma$-fields of $\mathcal A$. Then, $\Sigma(\mathcal A)$ is ...
passerby51's user avatar
  • 1,731
1 vote
1 answer
211 views

Can we order random variables in a measurable way in a general setup?

Let $(\Omega,\mathcal A,\operatorname P)$ be a probability space $(E,\mathcal E)$ be a measurable space $n\in\mathbb N$ $X_1,\ldots,X_n$ be $(E,\mathcal E)$-valued random variables on $(\Omega,\...
0xbadf00d's user avatar
  • 167
1 vote
0 answers
36 views

Does a total preorder on lotteries that preserves countable mixtures preserve arbitrary mixtures?

Let $X$ be a countable set. A lottery on $X$ is a function $\lambda: X \to [0,1]$ such that $\sum_x \lambda(x) = 1$. Let $\Delta X$ be the set of lotteries on $X$. A total preorder $\preceq$ on $\...
aduh's user avatar
  • 869