Polynomial Wolff axioms and Kakeya-type estimates in $\mathbb{R}^4$
Larry Guth, Joshua Zahl
备注:
30 pages, 0 figures. v3: An error has been corrected, which weakens the dimension of our maximal function estimate to 3 + 1/40. Previously, a bound of 3 + 1/28 was claimed. See the addendum following the statement of Theorem 1.1 for details
We establish new linear and trilinear bounds for collections of tubes in $\mathbb{R}^4$ that satisfy the polynomial Wolff axioms. In brief, a collection of $δ$-tubes satisfies the Wolff axioms if not too many tubes can be contained in the $δ$-neighborhood of a plane. A collection of tubes satisfies the polynomial Wolff axioms if not too many tubes can be contained in the $δ$-neighborhood of a low degree algebraic variety.
First, we prove that if a set of $δ^{-3}$ tubes in $\mathbb{R}^4$ satisfies the polynomial Wolff axioms, then the union of the tubes must have volume at least $δ^{1-1/40}$. We also prove a more technical statement which is analogous to a maximal function estimate at dimension $3+1/40$. Second, we prove that if a collection of $δ^{-3}$ tubes in $\mathbb{R}^4$ satisfies the polynomial Wolff axioms, and if most triples of intersecting tubes point in three linearly independent directions, then the union of the tubes must have volume at least $δ^{3/4}$. Again, we also prove a slightly more technical statement which is analogous to a maximal function estimate at dimension $3+1/4$.
We conjecture that every Kakeya set satisfies the polynomial Wolff axioms, but we are unable to prove this. If our conjecture is correct, it implies a Kakeya maximal function estimate at dimension $3+1/40$, and in particular this implies that every Kakeya set in $\mathbb{R}^4$ must have Hausdorff dimension at least $3+1/40$. This would be an improvement over the current best bound of 3, which was established by Wolff in 1995.
Kakeya and Furstenberg problems for sticky sets of tubes
Courant Institute of Mathematical Sciences, New York University(纽约大学柯朗数学科学研究所);Department of Mathematics, Massachusetts Institute of Technology(麻省理工学院数学系)
The Kakeya problem for codimension-two planes in $\mathbb{R}^n$
San Francisco State University(旧金山州立大学);University of Pennsylvania(宾夕法尼亚大学);Georgia Institute of Technology(佐治亚理工学院);University of British Columbia(不列颠哥伦比亚大学)