Kakeya tube
= Kakeya tube
{c}
{title2=$|T_\delta|\asymp_n\delta^{n-1}$}
A Kakeya tube is a neighborhood of transverse radius $\delta$ of a line segment of fixed unit length. Round cross-sections and comparable rectangular cross-sections are interchangeable up to fixed constants. The tube has <Lebesgue measure> comparable to $\delta^{n-1}$ in $\mathbb R^n$.