<p>Let <i>G</i> be a simple graph. We say that a hypergraph <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\cal{H}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">H</mi> </mrow> </math></EquationSource> </InlineEquation> is a Berge-<i>G</i> if there is a bijection <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\psi : E(G)\rightarrow E({\cal{H}}))\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mi>ψ</mi> <mo>:</mo> <mi>E</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> <mo stretchy="false">→</mo> <mi>E</mi> <mo stretchy="false">(</mo> <mrow> <mrow> <mi mathvariant="script">H</mi> </mrow> </mrow> <mo stretchy="false">)</mo> <mo stretchy="false">)</mo> </math></EquationSource> </InlineEquation> such that <i>e</i> ⊆ <i>ψ</i>(<i>e</i>) for all <i>e</i> ∈ <i>E</i>(<i>G</i>). For any <i>r</i>-uniform hypergraph <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\cal{H}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">H</mi> </mrow> </math></EquationSource> </InlineEquation> and a real number <i>p</i> ≥ 1, the <i>p</i>-spectral radius of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\cal{H}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi mathvariant="script">H</mi> </mrow> </math></EquationSource> </InlineEquation> is defined as <Equation ID="Equ1"> <EquationSource Format="TEX">\({\lambda^{(p)}}({\cal{H}}) = \mathop{\max}\limits_{x \in{\mathbb{R}^n},{{\| x \|}_p} = 1} r\mathop{\sum}\limits_{\{{{i_1},{i_2}, \ldots,{i_r}}\} \in E({\cal{H}})}{x_{{i_1}}}{x_{{i_2}}} \cdots{x_{{i_r}}}.\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msup> <mi>λ</mi> <mrow> <mo stretchy="false">(</mo> <mi>p</mi> <mo stretchy="false">)</mo> </mrow> </msup> </mrow> <mo stretchy="false">(</mo> <mrow> <mrow> <mi mathvariant="script">H</mi> </mrow> </mrow> <mo stretchy="false">)</mo> <mo>=</mo> <munder> <mrow> <mo form="prefix">max</mo> </mrow> <mrow> <mi>x</mi> <mo>∈</mo> <mrow> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> </mrow> <mo>,</mo> <mrow> <msub> <mrow> <mo fence="false" stretchy="false">∥</mo> <mi>x</mi> <mo fence="false" stretchy="false">∥</mo> </mrow> <mi>p</mi> </msub> </mrow> <mo>=</mo> <mn>1</mn> </mrow> </munder> <mo /> <mi>r</mi> <munder> <mrow> <mo movablelimits="false">∑</mo> </mrow> <mrow> <mo fence="false" stretchy="false">{</mo> <mrow> <mrow> <msub> <mi>i</mi> <mn>1</mn> </msub> </mrow> <mo>,</mo> <mrow> <msub> <mi>i</mi> <mn>2</mn> </msub> </mrow> <mo>,</mo> <mo>…</mo> <mo>,</mo> <mrow> <msub> <mi>i</mi> <mi>r</mi> </msub> </mrow> </mrow> <mo fence="false" stretchy="false">}</mo> <mo>∈</mo> <mi>E</mi> <mo stretchy="false">(</mo> <mrow> <mrow> <mi mathvariant="script">H</mi> </mrow> </mrow> <mo stretchy="false">)</mo> </mrow> </munder> <mo /> <mrow> <msub> <mi>x</mi> <mrow> <mrow> <msub> <mi>i</mi> <mn>1</mn> </msub> </mrow> </mrow> </msub> </mrow> <mrow> <msub> <mi>x</mi> <mrow> <mrow> <msub> <mi>i</mi> <mn>2</mn> </msub> </mrow> </mrow> </msub> </mrow> <mo>⋯</mo> <mrow> <msub> <mi>x</mi> <mrow> <mrow> <msub> <mi>i</mi> <mi>r</mi> </msub> </mrow> </mrow> </msub> </mrow> <mo>.</mo> </math></EquationSource> </Equation> A keyring <i>C</i><sub><i>n</i></sub>(<i>k</i>) is a graph of order <i>n</i> obtained from a cycle of length <i>n</i> − <i>k</i> by appending <i>k</i> leaves to one of vertices of the cycle. In this paper, we obtain the 3-uniform hypergraphs with maximum <i>p</i>-spectral radius for <i>p</i> ≥ 1 among 3-uniform Berge-<i>G</i> hypergraphs when <i>G</i> is a keyring.</p>

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The p-spectral Radius of Berge-keyring Hypergraphs

  • Xue Ji,
  • Liying Kang

摘要

Let G be a simple graph. We say that a hypergraph \(\cal{H}\) H is a Berge-G if there is a bijection \(\psi : E(G)\rightarrow E({\cal{H}}))\) ψ : E ( G ) E ( H ) ) such that eψ(e) for all eE(G). For any r-uniform hypergraph \(\cal{H}\) H and a real number p ≥ 1, the p-spectral radius of \(\cal{H}\) H is defined as \({\lambda^{(p)}}({\cal{H}}) = \mathop{\max}\limits_{x \in{\mathbb{R}^n},{{\| x \|}_p} = 1} r\mathop{\sum}\limits_{\{{{i_1},{i_2}, \ldots,{i_r}}\} \in E({\cal{H}})}{x_{{i_1}}}{x_{{i_2}}} \cdots{x_{{i_r}}}.\) λ ( p ) ( H ) = max x R n , x p = 1 r { i 1 , i 2 , , i r } E ( H ) x i 1 x i 2 x i r . A keyring Cn(k) is a graph of order n obtained from a cycle of length nk by appending k leaves to one of vertices of the cycle. In this paper, we obtain the 3-uniform hypergraphs with maximum p-spectral radius for p ≥ 1 among 3-uniform Berge-G hypergraphs when G is a keyring.