<p>In [<CitationRef CitationID="CR10">10</CitationRef>], Hibi and Mahmood introduced a sequence of simplicial complexes associated with a given simplicial complex <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\Omega \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">Ω</mi> </math></EquationSource> </InlineEquation> on the vertex set <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\([n] = \{1, 2, \ldots , n\}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">[</mo> <mi>n</mi> <mo stretchy="false">]</mo> <mo>=</mo> <mo stretchy="false">{</mo> <mn>1</mn> <mo>,</mo> <mn>2</mn> <mo>,</mo> <mo>…</mo> <mo>,</mo> <mi>n</mi> <mo stretchy="false">}</mo> </mrow> </math></EquationSource> </InlineEquation>, where each term in the sequence is obtained by taking the Stanley–Reisner complex of the facet ideal of the previous term. They proved that this sequence eventually returns to the original complex <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\Omega \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">Ω</mi> </math></EquationSource> </InlineEquation> after a finite number of steps and continues cyclically thereafter. The smallest such number <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(q\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>q</mi> </math></EquationSource> </InlineEquation> for which the <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\mathcal{N}\mathcal{F}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="script">N</mi> <mi mathvariant="script">F</mi> </mrow> </math></EquationSource> </InlineEquation>-complex is isomorphic to simplicial complex <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\Omega \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">Ω</mi> </math></EquationSource> </InlineEquation>, that is, <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\gamma ^{(q)}_{\mathcal{N}\mathcal{F}}(\Omega ) \cong \Omega \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>γ</mi> <mrow> <mi mathvariant="script">N</mi> <mi mathvariant="script">F</mi> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>q</mi> <mo stretchy="false">)</mo> </mrow> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="normal">Ω</mi> <mo stretchy="false">)</mo> </mrow> <mo>≅</mo> <mi mathvariant="normal">Ω</mi> </mrow> </math></EquationSource> </InlineEquation>, is called the <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\mathcal{N}\mathcal{F}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="script">N</mi> <mi mathvariant="script">F</mi> </mrow> </math></EquationSource> </InlineEquation>-number of <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\Omega \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="normal">Ω</mi> </math></EquationSource> </InlineEquation>. In this paper, we show that the <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\mathcal{N}\mathcal{F}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="script">N</mi> <mi mathvariant="script">F</mi> </mrow> </math></EquationSource> </InlineEquation>-number of <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(m\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>m</mi> </math></EquationSource> </InlineEquation> disjoint copies of the complete graph <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\(K_n\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>K</mi> <mi>n</mi> </msub> </math></EquationSource> </InlineEquation> is <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(mn + 2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>m</mi> <mi>n</mi> <mo>+</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation>.</p>

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Expected \(\mathcal {N}\mathcal {F}\)-number of disjoint union of finite copies of complete graph

  • Hafiz Muhammad Bilal,
  • Sarfraz Ahmad,
  • Hasan Mahmood,
  • Muhammad Ahsan Binyamin

摘要

In [10], Hibi and Mahmood introduced a sequence of simplicial complexes associated with a given simplicial complex \(\Omega \) Ω on the vertex set \([n] = \{1, 2, \ldots , n\}\) [ n ] = { 1 , 2 , , n } , where each term in the sequence is obtained by taking the Stanley–Reisner complex of the facet ideal of the previous term. They proved that this sequence eventually returns to the original complex \(\Omega \) Ω after a finite number of steps and continues cyclically thereafter. The smallest such number \(q\) q for which the \(\mathcal{N}\mathcal{F}\) N F -complex is isomorphic to simplicial complex \(\Omega \) Ω , that is, \(\gamma ^{(q)}_{\mathcal{N}\mathcal{F}}(\Omega ) \cong \Omega \) γ N F ( q ) ( Ω ) Ω , is called the \(\mathcal{N}\mathcal{F}\) N F -number of \(\Omega \) Ω . In this paper, we show that the \(\mathcal{N}\mathcal{F}\) N F -number of \(m\) m disjoint copies of the complete graph \(K_n\) K n is \(mn + 2\) m n + 2 .