<p>Let <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="72" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>p</mi> <mn>1</mn> </msub> <mo>,</mo> <mo>…</mo> <mo>,</mo> <msub> <mi>p</mi> <mi>n</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">$p_{1},\ldots ,p_{n}$</EquationSource> </InlineEquation> be a set of points in the unit square and let <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq2.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="74" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mn>1</mn> </msub> <mo>,</mo> <mo>…</mo> <mo>,</mo> <msub> <mi>T</mi> <mi>n</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">$T_{1},\ldots ,T_{n}$</EquationSource> </InlineEquation> be a set of <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="12" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>δ</mi> </math></EquationSource> <EquationSource Format="TEX">$\delta $</EquationSource> </InlineEquation>-tubes such that <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>T</mi> <mi>j</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">$T_{j}$</EquationSource> </InlineEquation> passes through <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq5.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>p</mi> <mi>j</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">$p_{j}$</EquationSource> </InlineEquation>. We prove a lower bound for the number of incidences between the points and tubes under a natural regularity condition (similar to Frostman regularity). As a consequence, we show that in any configuration of points <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq6.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="130" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>p</mi> <mn>1</mn> </msub> <mo>,</mo> <mo>…</mo> <mo>,</mo> <msub> <mi>p</mi> <mi>n</mi> </msub> <mo>∈</mo> <msup> <mrow> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">]</mo> </mrow> <mn>2</mn> </msup> </math></EquationSource> <EquationSource Format="TEX">$p_{1},\ldots , p_{n} \in [0,1]^{2}$</EquationSource> </InlineEquation> along with a line <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="16" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>ℓ</mi> <mi>j</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">$\ell _{j}$</EquationSource> </InlineEquation> through each point <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq8.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>p</mi> <mi>j</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">$p_{j}$</EquationSource> </InlineEquation>, there exist <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq9.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="44" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>j</mi> <mo>≠</mo> <mi>k</mi> </math></EquationSource> <EquationSource Format="TEX">$j\neq k$</EquationSource> </InlineEquation> for which <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq10.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="148" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>d</mi> <mo stretchy="false">(</mo> <msub> <mi>p</mi> <mi>j</mi> </msub> <mo>,</mo> <msub> <mi>ℓ</mi> <mi>k</mi> </msub> <mo stretchy="false">)</mo> <mo>≲</mo> <msup> <mi>n</mi> <mrow> <mo>−</mo> <mn>2</mn> <mo stretchy="false">/</mo> <mn>3</mn> <mo>+</mo> <mi>o</mi> <mo stretchy="false">(</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </msup> </math></EquationSource> <EquationSource Format="TEX">$d(p_{j}, \ell _{k}) \lesssim n^{-2/3+o(1)}$</EquationSource> </InlineEquation>. It follows from the latter result that any set of <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq11.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>n</mi> </math></EquationSource> <EquationSource Format="TEX">$n$</EquationSource> </InlineEquation> points in the unit square contains three points forming a triangle of area at most <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="222_2025_1331_Article_IEq12.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="68" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msup> <mi>n</mi> <mrow> <mo>−</mo> <mn>7</mn> <mo stretchy="false">/</mo> <mn>6</mn> <mo>+</mo> <mi>o</mi> <mo stretchy="false">(</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </msup> </math></EquationSource> <EquationSource Format="TEX">$n^{-7/6+o(1)}$</EquationSource> </InlineEquation>. This new upper bound for Heilbronn’s triangle problem attains the high-low limit established in our previous work arXiv:<a href="http://arxiv.org/abs/2305.18253">2305.18253</a>.</p>

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Lower bounds for incidences

  • Alex Cohen,
  • Cosmin Pohoata,
  • Dmitrii Zakharov

摘要

Let p 1 , , p n $p_{1},\ldots ,p_{n}$ be a set of points in the unit square and let T 1 , , T n $T_{1},\ldots ,T_{n}$ be a set of δ $\delta $ -tubes such that T j $T_{j}$ passes through p j $p_{j}$ . We prove a lower bound for the number of incidences between the points and tubes under a natural regularity condition (similar to Frostman regularity). As a consequence, we show that in any configuration of points p 1 , , p n [ 0 , 1 ] 2 $p_{1},\ldots , p_{n} \in [0,1]^{2}$ along with a line j $\ell _{j}$ through each point p j $p_{j}$ , there exist j k $j\neq k$ for which d ( p j , k ) n 2 / 3 + o ( 1 ) $d(p_{j}, \ell _{k}) \lesssim n^{-2/3+o(1)}$ . It follows from the latter result that any set of n $n$ points in the unit square contains three points forming a triangle of area at most n 7 / 6 + o ( 1 ) $n^{-7/6+o(1)}$ . This new upper bound for Heilbronn’s triangle problem attains the high-low limit established in our previous work arXiv:2305.18253.