<p>A graph <i>G</i> is said to be <i>M</i>-integral (resp. <i>A</i>-integral, <i>D</i>-integral, <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq2.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="26" /> </InlineMediaObject> <EquationSource Format="TEX">\(D^L\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>D</mi> <mi>L</mi> </msup> </math></EquationSource> </InlineEquation>-integral or <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq1.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">\(D^Q\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>D</mi> <mi>Q</mi> </msup> </math></EquationSource> </InlineEquation>-integral) if all eigenvalues of its matrix <i>M</i> (resp. adjacency matrix <i>A</i>(<i>G</i>) , distance matrix <i>D</i>(<i>G</i>) , distance Laplacian matrix <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq9.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="50" /> </InlineMediaObject> <EquationSource Format="TEX">\(D^L(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>D</mi> <mi>L</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> or distance signless Laplacian matrix <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq10.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="51" /> </InlineMediaObject> <EquationSource Format="TEX">\(D^Q(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>D</mi> <mi>Q</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>) are integers. Lu et al. [Discrete Math, 346 (2023)] defined the generalized wheel graph <i>GW</i>(<i>a</i>,&#xa0;<i>m</i>,&#xa0;<i>n</i>) as the graph <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq11.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="70" /> </InlineMediaObject> <EquationSource Format="TEX">\(aK_{m}\nabla C_{n}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <msub> <mi>K</mi> <mi>m</mi> </msub> <mi mathvariant="normal">∇</mi> <msub> <mi>C</mi> <mi>n</mi> </msub> </mrow> </math></EquationSource> </InlineEquation>, and obtained all <i>D</i>-integral generalized wheel graphs <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq12.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="70" /> </InlineMediaObject> <EquationSource Format="TEX">\(aK_{m} \nabla C_{n}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <msub> <mi>K</mi> <mi>m</mi> </msub> <mi mathvariant="normal">∇</mi> <msub> <mi>C</mi> <mi>n</mi> </msub> </mrow> </math></EquationSource> </InlineEquation>. Based on the above research, in this paper, we determine all <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq2.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="26" /> </InlineMediaObject> <EquationSource Format="TEX">\(D^L\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>D</mi> <mi>L</mi> </msup> </math></EquationSource> </InlineEquation>-integral and <InlineEquation ID="IEq14"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq1.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="28" /> </InlineMediaObject> <EquationSource Format="TEX">\(D^Q\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>D</mi> <mi>Q</mi> </msup> </math></EquationSource> </InlineEquation>-integral generalized wheel graphs <InlineEquation ID="IEq15"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq15.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="70" /> </InlineMediaObject> <EquationSource Format="TEX">\(aK_{m} \nabla C_{n} \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>a</mi> <msub> <mi>K</mi> <mi>m</mi> </msub> <mi mathvariant="normal">∇</mi> <msub> <mi>C</mi> <mi>n</mi> </msub> </mrow> </math></EquationSource> </InlineEquation> respectively. As byproducts, we give a sufficient and necessary condition for the join <InlineEquation ID="IEq16"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq16.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="55" /> </InlineMediaObject> <EquationSource Format="TEX">\( G_{1} \nabla G_{2} \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>G</mi> <mn>1</mn> </msub> <mi mathvariant="normal">∇</mi> <msub> <mi>G</mi> <mn>2</mn> </msub> </mrow> </math></EquationSource> </InlineEquation> of two regular graphs <InlineEquation ID="IEq17"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq17.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\( G_{1}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>G</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq18"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq18.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\(G_{2} \)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>G</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> to be <InlineEquation ID="IEq19"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq19.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="26" /> </InlineMediaObject> <EquationSource Format="TEX">\( D^{L} \)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>D</mi> <mi>L</mi> </msup> </math></EquationSource> </InlineEquation>-integral, from which we can get infinitely many new classes of <InlineEquation ID="IEq20"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13226_2025_835_Article_IEq19.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="26" /> </InlineMediaObject> <EquationSource Format="TEX">\( D^{L} \)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>D</mi> <mi>L</mi> </msup> </math></EquationSource> </InlineEquation>-integral graphs.</p>

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\(D^Q\)-integral and \(D^L\)-integral generalized wheel graphs

  • Yirui Chai,
  • Ligong Wang,
  • Yuwei Zhou

摘要

A graph G is said to be M-integral (resp. A-integral, D-integral, \(D^L\) D L -integral or \(D^Q\) D Q -integral) if all eigenvalues of its matrix M (resp. adjacency matrix A(G) , distance matrix D(G) , distance Laplacian matrix \(D^L(G)\) D L ( G ) or distance signless Laplacian matrix \(D^Q(G)\) D Q ( G ) ) are integers. Lu et al. [Discrete Math, 346 (2023)] defined the generalized wheel graph GW(amn) as the graph \(aK_{m}\nabla C_{n}\) a K m C n , and obtained all D-integral generalized wheel graphs \(aK_{m} \nabla C_{n}\) a K m C n . Based on the above research, in this paper, we determine all \(D^L\) D L -integral and \(D^Q\) D Q -integral generalized wheel graphs \(aK_{m} \nabla C_{n} \) a K m C n respectively. As byproducts, we give a sufficient and necessary condition for the join \( G_{1} \nabla G_{2} \) G 1 G 2 of two regular graphs \( G_{1}\) G 1 and \(G_{2} \) G 2 to be \( D^{L} \) D L -integral, from which we can get infinitely many new classes of \( D^{L} \) D L -integral graphs.