Let $T:\mathbb{R}/\mathbb{Z}\rightarrow \mathbb{R}/\mathbb{Z}$ be the map defined by $T(x)=2x$, and suppose that $\mu$ is a $T$ invariant and ergodic Borel probability measure on the space, which is not a finite sum of point masses. What if anything can be said about the decay of the Fourier transform of $\mu$? \mu$, along the sequence of odd integers (to take into account Andreas's comment below)?
For example is it true that $\hat{\mu}(n)\ll \hat{\mu}(2n+1)\ll |n|^{-c}$ 2n+1|^{-c}$ for some $c>0$?
If it helps to answer the question (or in case the answer is no in general) I would also be happy to know, what can be said under the additional hypothesis that $T$ has positive measure theoretic entropy with respect to $\mu$?
