A noninequality for the fractional gradient

  title={A noninequality for the fractional gradient},
  author={Daniel Spector},
  journal={arXiv: Classical Analysis and ODEs},
  • Daniel Spector
  • Published 13 June 2019
  • Mathematics
  • arXiv: Classical Analysis and ODEs
In this paper we give a streamlined proof of an inequality recently obtained by the author: For every $\alpha \in (0,1)$ there exists a constant $C=C(\alpha,d)>0$ such that \begin{align*} \|u\|_{L^{d/(d-\alpha),1}(\mathbb{R}^d)} \leq C \| D^\alpha u\|_{L^1(\mathbb{R}^d;\mathbb{R}^d)} \end{align*} for all $u \in L^q(\mathbb{R}^d)$ for some $1 \leq q<d/(1-\alpha)$ such that $D^\alpha u:=\nabla I_{1-\alpha} u \in L^1(\mathbb{R}^d;\mathbb{R}^d)$. We also give a counterexample which shows that in… Expand
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