Sparse form domination implies worse sparse form domination

Let r(0,)m\vec{r}\in(0,\infty)^m, q0(0,)q_0\in(0,\infty), and s(q0,]s\in(q_0,\infty]. Let TT be an operator defined on mm-tuples of functions. Suppose that, for any f1,,fmLc(Rd)f_1,\ldots,f_m\in L^\infty_c(\mathbf{R}^d) and some function gg, there exists a sparse collection S\mathcal{S} such that

T(f)gLq0(Rd)(QS(j=1mfjrj,Q)q0g11q01s,Qq0Q)1q0.\|T(\vec{f})\cdot g\|_{L^{q_0}(\mathbf{R}^d)}\lesssim \left(\sum_{Q\in\mathcal{S}}\left(\prod_{j=1}^m\langle f_j\rangle_{r_j,Q}\right)^{q_0}\langle g\rangle^{q_0}_{\frac{1}{\frac{1}{q_0}-\frac{1}{s}},Q}|Q|\right)^{\frac{1}{q_0}}.

Sparse form domination conjecture. The same estimate should also hold after replacing q0q_0 by any q(0,q0]q\in(0,q_0].

This conjecture asks whether sparse domination in form at exponent q0q_0 automatically yields the corresponding, quantitatively weaker, sparse form estimates at all smaller exponents. The text notes that such replacement would give qualitatively the same weighted bounds, but with a worse exponent; whether the needed flexibility follows automatically is unknown.

Sources & referencesView supporting material

Primary source

Emiel Lorist and Zoe Nieraeth, “Sparse domination implies vector-valued sparse domination”, arXiv:2003.02233 (2021).

Additional references

3 papers in this index state this conjecture (2016–2020). The statement above is taken from the most recent of them; the others are arXiv:1609.06364, arXiv:1601.03193.

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