<p>As a higher analogue of the edge ideal of a graph, we study the <i>t</i>-connected ideal <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10801_2025_1395_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\,\textrm{J}\,}}_{t}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mspace width="0.166667em" /> <mtext>J</mtext> <mspace width="0.166667em" /> </mrow> <mi>t</mi> </msub> </math></EquationSource> </InlineEquation>. This is the monomial ideal generated by the connected subsets of size <i>t</i>. For chordal graphs, we show that <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10801_2025_1395_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\,\textrm{J}\,}}_{t}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mrow> <mspace width="0.166667em" /> <mtext>J</mtext> <mspace width="0.166667em" /> </mrow> <mi>t</mi> </msub> </math></EquationSource> </InlineEquation> has a linear resolution iff the graph is <i>t</i>-gap-free, and that this is equivalent to having linear quotients. We then show that if <i>G</i> is any gap-free and <i>t</i>-claw-free graph, then <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10801_2025_1395_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\,\textrm{J}\,}}_{t}(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mrow> <mspace width="0.166667em" /> <mtext>J</mtext> <mspace width="0.166667em" /> </mrow> <mi>t</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> has linear quotients and, hence, linear resolution.</p>

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Linear quotients of connected ideals of graphs

  • H. Ananthnarayan,
  • Omkar Javadekar,
  • Aryaman Maithani

摘要

As a higher analogue of the edge ideal of a graph, we study the t-connected ideal \({{\,\textrm{J}\,}}_{t}\) J t . This is the monomial ideal generated by the connected subsets of size t. For chordal graphs, we show that \({{\,\textrm{J}\,}}_{t}\) J t has a linear resolution iff the graph is t-gap-free, and that this is equivalent to having linear quotients. We then show that if G is any gap-free and t-claw-free graph, then \({{\,\textrm{J}\,}}_{t}(G)\) J t ( G ) has linear quotients and, hence, linear resolution.