<p>We say that a <i>cubical 2-knot</i> <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(K^{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>K</mi> <mn>2</mn> </msup> </math></EquationSource> </InlineEquation> is an embedding of the 2-sphere in the 2-skeleton of the canonical cubulation of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\mathbb {R}^4\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mn>4</mn> </msup> </math></EquationSource> </InlineEquation>; in particular, <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(K^{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>K</mi> <mn>2</mn> </msup> </math></EquationSource> </InlineEquation> is the union of <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(m(K^{2})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>m</mi> <mo stretchy="false">(</mo> <msup> <mi>K</mi> <mn>2</mn> </msup> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> unit squares, and hence, <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(m(K^{2})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>m</mi> <mo stretchy="false">(</mo> <msup> <mi>K</mi> <mn>2</mn> </msup> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is its area. We define the minimal area of <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(K^{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>K</mi> <mn>2</mn> </msup> </math></EquationSource> </InlineEquation> as the minimum over all the areas of cubical 2-knots isotopic to the given knot type. The minimal area of a cubical 2-knot is an invariant, and the following natural question arose: Given a knot type, what area is needed for a cubical 2-knot in the canonical cubulation of <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\mathbb {R}^4\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mn>4</mn> </msup> </math></EquationSource> </InlineEquation> to realise that type with minimal area? In this paper, we answer this question for the spun trefoil knot in the weakly minimal case.</p>

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Minimal area of the spun trefoil knot on the canonical cubulation of \(\mathbb {R}^4\)

  • Ana Baray,
  • Juan José Catalán,
  • Gabriela Hinojosa,
  • Rogelio Valdez

摘要

We say that a cubical 2-knot \(K^{2}\) K 2 is an embedding of the 2-sphere in the 2-skeleton of the canonical cubulation of \(\mathbb {R}^4\) R 4 ; in particular, \(K^{2}\) K 2 is the union of \(m(K^{2})\) m ( K 2 ) unit squares, and hence, \(m(K^{2})\) m ( K 2 ) is its area. We define the minimal area of \(K^{2}\) K 2 as the minimum over all the areas of cubical 2-knots isotopic to the given knot type. The minimal area of a cubical 2-knot is an invariant, and the following natural question arose: Given a knot type, what area is needed for a cubical 2-knot in the canonical cubulation of \(\mathbb {R}^4\) R 4 to realise that type with minimal area? In this paper, we answer this question for the spun trefoil knot in the weakly minimal case.