Polynomial Roth theorems on sets of fractional dimensions

Abstract

Let $E\subset \mathbb{R}$ be a closed set of Hausdorff dimension $\alpha \in (0,1)$. Let $P:\mathbb{R}\to \mathbb{R}$ be a polynomial without a constant term whose degree is bigger than one. We prove that if $E$ supports a probability measure satisfying certain dimension condition and Fourier decay condition, then $E$ contains three points $x,x+t,x+P(t)$ for some $t>0$. Our result extends the one of Laba and the third author to the polynomial setting, under the same assumption. It also gives an affirmative answer to a question in Henriot, Laba and the third author.

16 pages