<p>Let <i>G</i> be a connected graph of minimum degree at least two. A set <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(D\subseteq V(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>D</mi> <mo>⊆</mo> <mi>V</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is a double total dominating set of <i>G</i> if <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(|N_G(v)\cap D|\ge 2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>N</mi> <mi>G</mi> </msub> <mrow> <mrow> <mo stretchy="false">(</mo> <mi>v</mi> <mo stretchy="false">)</mo> </mrow> <mo>∩</mo> <mi>D</mi> <mo stretchy="false">|</mo> <mo>≥</mo> <mn>2</mn> </mrow> </mrow> </math></EquationSource> </InlineEquation> for every vertex <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(v\in V(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>v</mi> <mo>∈</mo> <mi>V</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, where <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(N_G(v)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>N</mi> <mi>G</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>v</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> represents the open neighborhood of <i>v</i>. The double total domination number of <i>G</i> is the minimum cardinality among all double total dominating sets of <i>G</i>. In this article we study this parameter in some well-known graph operators defined from a connected graph <i>G</i>. In particular, we obtain the exact value for the double total domination number of the graph operator <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\texttt{R}(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="monospace">R</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and the central graph <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\texttt{C}(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="monospace">C</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>. In addition, we obtain closed formulas for the double total domination number of the middle graph <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\texttt{M}(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="monospace">M</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, the subdivision graph <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\texttt{S}(G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="monospace">S</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and the Mycielskian graph <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\mu (G)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>μ</mi> <mo stretchy="false">(</mo> <mi>G</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>.</p>

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Double Total Domination Number of Some Graph Operators

  • Ismael Rios-Villamar,
  • Abel Cabrera-Martínez,
  • Gerardo Reyna Hernández,
  • José M. Sigarreta

摘要

Let G be a connected graph of minimum degree at least two. A set \(D\subseteq V(G)\) D V ( G ) is a double total dominating set of G if \(|N_G(v)\cap D|\ge 2\) | N G ( v ) D | 2 for every vertex \(v\in V(G)\) v V ( G ) , where \(N_G(v)\) N G ( v ) represents the open neighborhood of v. The double total domination number of G is the minimum cardinality among all double total dominating sets of G. In this article we study this parameter in some well-known graph operators defined from a connected graph G. In particular, we obtain the exact value for the double total domination number of the graph operator \(\texttt{R}(G)\) R ( G ) and the central graph \(\texttt{C}(G)\) C ( G ) . In addition, we obtain closed formulas for the double total domination number of the middle graph \(\texttt{M}(G)\) M ( G ) , the subdivision graph \(\texttt{S}(G)\) S ( G ) and the Mycielskian graph \(\mu (G)\) μ ( G ) .