<p>Equipartition theory, beginning with the classical ham sandwich theorem, seeks the fair division of finite point sets in <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathbb {R}^d\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>d</mi> </msup> </math></EquationSource> </InlineEquation> by the full-dimensional regions determined by a prescribed geometric dissection of <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\mathbb {R}^d\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>d</mi> </msup> </math></EquationSource> </InlineEquation>. Here we examine <i>equidistributions</i> of finite point sets in <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\mathbb {R}^d\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>d</mi> </msup> </math></EquationSource> </InlineEquation> by prescribed <i>low dimensional</i> subsets of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\mathbb {R}^d\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>d</mi> </msup> </math></EquationSource> </InlineEquation>. Our main result states that if <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(r\ge 3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>r</mi> <mo>≥</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation> is a prime power, then for any <i>m</i>-coloring of a sufficiently small point set <i>X</i> in <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\mathbb {R}^d\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>d</mi> </msup> </math></EquationSource> </InlineEquation>, there exists an <i>r</i>-fan in <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\mathbb {R}^d\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>d</mi> </msup> </math></EquationSource> </InlineEquation> – that is, the union of <i>r</i> “half-flats” of codimension <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(r-2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>r</mi> <mo>-</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation> centered about a common <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\((r-1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>r</mi> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>-codimensional affine subspace – which captures all the points of <i>X</i> in such a way that each half-flat contains at most an <i>r</i>-th of the points from each color class. The number of points in <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\mathbb {R}^d\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>d</mi> </msup> </math></EquationSource> </InlineEquation> we require for this is essentially sharp when <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(m\ge 2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>m</mi> <mo>≥</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation> and in particular is asymptotically tight. Additionally, we extend our equidistribution results to “piercing” distributions in a similar fashion to Dolnikov’s hyperplane transversal generalization of the ham sandwich theorem. By analogy with recent work of Frick et al., our results are obtained by applying Gale duality to linear cases of topological Tverberg-type theorems. Finally, we extend our distribution results to multiple <i>r</i>-fans after establishing a multiple intersection version of a topological Tverberg-type theorem due to Sarkaria.</p>

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Fan Distributions Via Tverberg Partitions and Gale Duality

  • Shuai Huang,
  • Jasper Miller,
  • Daniel Rose-Levine,
  • Steven Simon

摘要

Equipartition theory, beginning with the classical ham sandwich theorem, seeks the fair division of finite point sets in \(\mathbb {R}^d\) R d by the full-dimensional regions determined by a prescribed geometric dissection of \(\mathbb {R}^d\) R d . Here we examine equidistributions of finite point sets in \(\mathbb {R}^d\) R d by prescribed low dimensional subsets of \(\mathbb {R}^d\) R d . Our main result states that if \(r\ge 3\) r 3 is a prime power, then for any m-coloring of a sufficiently small point set X in \(\mathbb {R}^d\) R d , there exists an r-fan in \(\mathbb {R}^d\) R d – that is, the union of r “half-flats” of codimension \(r-2\) r - 2 centered about a common \((r-1)\) ( r - 1 ) -codimensional affine subspace – which captures all the points of X in such a way that each half-flat contains at most an r-th of the points from each color class. The number of points in \(\mathbb {R}^d\) R d we require for this is essentially sharp when \(m\ge 2\) m 2 and in particular is asymptotically tight. Additionally, we extend our equidistribution results to “piercing” distributions in a similar fashion to Dolnikov’s hyperplane transversal generalization of the ham sandwich theorem. By analogy with recent work of Frick et al., our results are obtained by applying Gale duality to linear cases of topological Tverberg-type theorems. Finally, we extend our distribution results to multiple r-fans after establishing a multiple intersection version of a topological Tverberg-type theorem due to Sarkaria.