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Tom
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This is impossible if $f$ is invertible. Let $Q_1,Q_2$ be distributions, and assume $f_* Q_1 = f_* Q_2$ for some invertible (measurable) $f$. For any Borel set $B$, definitions give

$$ Q_1(B) = f_* Q_1 (f(B)) = f_* Q_2 (f(B)) = Q_2(B). $$

Thus, $Q_1 = Q_2$.

Tom
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