Hardy inequalities in Triebel--Lizorkin spaces Lizaveta IhnatsyevaAntti Vähäkangas 46E35Ahlfors d-regular setHardy inequalitypointwise multiplierextension theoremlocal polynomial approximation We prove an inequality of Hardy type for functions in Triebel-Lizorkin spaces. The distance involved is measured to a given Ahlfors $d$-regular set in $\mathbb{R}^n$, with $n-1<d<n$. As an application of the Hardy inequality, we consider boundedness of pointwise multiplication operators, and extension problems. Indiana University Mathematics Journal 2013 text pdf 10.1512/iumj.2013.62.5173 10.1512/iumj.2013.62.5173 en Indiana Univ. Math. J. 62 (2013) 1785 - 1807 state-of-the-art mathematics http://iumj.org/access/