<p>For each 1 ≤ <i>i</i> ≤ <i>n</i>, let <i>k</i><sub><i>i</i></sub> ≥ 1 and let Δ<sub><i>i</i></sub> be a set of vertices of a non-degenerate simplex of <i>k</i><sub><i>i</i></sub> + 1 points in <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11856_2024_2710_Article_IEq1.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="37" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathbb R}^{{k_{i}}+1}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <msup> <mrow> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> </mrow> <mrow> <mrow> <msub> <mi>k</mi> <mrow> <mi>i</mi> </mrow> </msub> </mrow> <mo>+</mo> <mn>1</mn> </mrow> </msup> </math></EquationSource> </InlineEquation>. If <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11856_2024_2710_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="218" /> </InlineMediaObject> <EquationSource Format="TEX">\(A \subseteq [0,1]^{k_{1}+1} \times \cdots \times [0,1]^{{k_{n}}+1}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi>A</mi> <mo>⊆</mo> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <msup> <mo stretchy="false">]</mo> <mrow> <msub> <mi>k</mi> <mrow> <mn>1</mn> </mrow> </msub> <mo>+</mo> <mn>1</mn> </mrow> </msup> <mo>×</mo> <mo>⋯</mo> <mo>×</mo> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <msup> <mo stretchy="false">]</mo> <mrow> <mrow> <msub> <mi>k</mi> <mrow> <mi>n</mi> </mrow> </msub> </mrow> <mo>+</mo> <mn>1</mn> </mrow> </msup> </math></EquationSource> </InlineEquation> is a Lebesgue measurable set of measure at least <i>δ</i>, we show that there exists an interval <i>I</i> = <i>I</i>(Δ<sub>1</sub>,…,Δ<sub><i>n</i></sub>, <i>A</i>) of length at least <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11856_2024_2710_Article_IEq3.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="135" /> </InlineMediaObject> <EquationSource Format="TEX">\(\exp(-\delta^{{-C}(\Delta_{1},\ldots,\Delta_{n})})\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi>exp</mi> <mo /> <mo stretchy="false">(</mo> <mo>−</mo> <msup> <mi>δ</mi> <mrow> <mrow> <mo>−</mo> <mi>C</mi> </mrow> <mo stretchy="false">(</mo> <msub> <mi mathvariant="normal">Δ</mi> <mrow> <mn>1</mn> </mrow> </msub> <mo>,</mo> <mo>…</mo> <mo>,</mo> <msub> <mi mathvariant="normal">Δ</mi> <mrow> <mi>n</mi> </mrow> </msub> <mo stretchy="false">)</mo> </mrow> </msup> <mo stretchy="false">)</mo> </math></EquationSource> </InlineEquation> such that for each <i>λ</i> ∈ <i>I</i>, the set <i>A</i> contains <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11856_2024_2710_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="105" /> </InlineMediaObject> <EquationSource Format="TEX">\({\Delta^{\prime}_{1}} \times \cdots \times {\Delta^{\prime}_{n}}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msubsup> <mi mathvariant="normal">Δ</mi> <mrow> <mn>1</mn> </mrow> <mrow> <mi class="MJX-variant" mathvariant="normal">′</mi> </mrow> </msubsup> </mrow> <mo>×</mo> <mo>⋯</mo> <mo>×</mo> <mrow> <msubsup> <mi mathvariant="normal">Δ</mi> <mrow> <mi>n</mi> </mrow> <mrow> <mi class="MJX-variant" mathvariant="normal">′</mi> </mrow> </msubsup> </mrow> </math></EquationSource> </InlineEquation>, where each <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11856_2024_2710_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\({\Delta^{\prime}_{i}}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msubsup> <mi mathvariant="normal">Δ</mi> <mrow> <mi>i</mi> </mrow> <mrow> <mi class="MJX-variant" mathvariant="normal">′</mi> </mrow> </msubsup> </mrow> </math></EquationSource> </InlineEquation> is an isometric copy of <i>λ</i>Δ<sub><i>i</i></sub>.This is a quantitative improvement of a result by Lyall and Magyar. Our proof relies on harmonic analysis. The main ingredient in the proof are cancellation estimates for forms similar to multilinear singular integrals associated with <i>n</i>-partite <i>n</i>-regular hypergraphs.</p>

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Quantitative bounds for products of simplices in subsets of the unit cube

  • Polona Durcik,
  • Mario Stipčić

摘要

For each 1 ≤ in, let ki ≥ 1 and let Δi be a set of vertices of a non-degenerate simplex of ki + 1 points in \({\mathbb R}^{{k_{i}}+1}\) R k i + 1 . If \(A \subseteq [0,1]^{k_{1}+1} \times \cdots \times [0,1]^{{k_{n}}+1}\) A [ 0 , 1 ] k 1 + 1 × × [ 0 , 1 ] k n + 1 is a Lebesgue measurable set of measure at least δ, we show that there exists an interval I = I1,…,Δn, A) of length at least \(\exp(-\delta^{{-C}(\Delta_{1},\ldots,\Delta_{n})})\) exp ( δ C ( Δ 1 , , Δ n ) ) such that for each λI, the set A contains \({\Delta^{\prime}_{1}} \times \cdots \times {\Delta^{\prime}_{n}}\) Δ 1 × × Δ n , where each \({\Delta^{\prime}_{i}}\) Δ i is an isometric copy of λΔi.This is a quantitative improvement of a result by Lyall and Magyar. Our proof relies on harmonic analysis. The main ingredient in the proof are cancellation estimates for forms similar to multilinear singular integrals associated with n-partite n-regular hypergraphs.