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Let us consider expanding maps $E_m: x\mapsto mx$ on the circle written additively. If we consider the set of all $E_2$ invariant probability Borel measures then the convex hull of atomic measures generated by $E_2$ periodic points are weak star dense in this set.

I want to ask whether this is true for the set of probability Borel measures invariant under both maps $E_2$ and $E_3.$

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Probably not, mathoverflow.net/questions/44234/… –  Andreas Thom Jan 10 '12 at 9:32
If the Furstenberg conjecture is true, then the answer is yes: The conjecture states that the invariant measures consist of precisely combinations of atomic measures and Lebesgue measure. Since Lebesgue measure is the weak* limit of the invariant measures $\mu_p=1/(p-1)\sum_{i=1}^{p-1}\delta_{i/p}$ for $p$ prime, we're done. –  Anthony Quas Jan 10 '12 at 16:15
Thank you for comments, especially for the link! –  user20471 Jan 10 '12 at 17:17

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