Improved bounds for radial projections in the plane

Abstract: We improve the best known lower bound for the dimension of radial projections of sets in the plane. We show that if $X,Y$ are Borel sets in $\R^2$, $X$ is not contained in any line and $\dim_H(X)>0$, then $$\sup\limits_{x\in X} \dim_H(\pi_x Y) \geq \min\left{(\dim_H(Y) + \dim_H(X))/2, \dim_H(Y), 1\right},$$ where $\pi_x Y$ is the radial projection of the set $Y$ from the point $x$.