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Conjecture Let
and
are filters on a set
and
. Then
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See here for some equivalent reformulations of this problem.
This problem (in fact, a little more general version of a problem equivalent to this problem) was solved by the problem author. See here for the solution.
Maybe this problem should be moved to "second-tier" because its solution is simple.
Bibliography
*Victor Porton. Open problem: co-separability of filter objects
* indicates original appearance(s) of problem.