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 <title>Open Problem Garden - Vertex Coloring of graph fractional powers - Comments</title>
 <link>http://www.openproblemgarden.org/op/vertex_coloring_of_graph_fractional_powers</link>
 <description>Comments for &quot;Vertex Coloring of graph fractional powers&quot;</description>
 <language>en</language>
<item>
 <title>Needs revision  (re: Vertex Coloring of graph fractional powers)</title>
 <link>http://www.openproblemgarden.org/op/vertex_coloring_of_graph_fractional_powers#comment-6991</link>
 <description>&lt;p&gt;Note that if K_t is the complete graph on t vertices with t even, then the 2-power of the 2-subdivision of K_t is isomorphic to the total graph of K_t. That is the graph T(K_t) whose vertex set is V(K_t) union E(K_t) and  two vertices are adjacent in T(K_t) if their either adjacent or incident in K_t.&lt;/p&gt;
&lt;p&gt;clique number of T(K_t) is t + 1 and the chromatic number of T(K_t) is &gt;= t+2.&lt;/p&gt;
</description>
 <pubDate>Wed, 13 Jul 2011 02:47:13 +0200</pubDate>
 <dc:creator>Anonymous</dc:creator>
 <guid isPermaLink="false">comment 6991 at http://www.openproblemgarden.org</guid>
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<item>
 <title>Vertex Coloring of graph fractional powers</title>
 <link>http://www.openproblemgarden.org/op/vertex_coloring_of_graph_fractional_powers</link>
 <description>&lt;table cellspacing=&quot;10&quot;&gt;
&lt;tr&gt;
  &lt;td&gt;
    Author(s):
        &lt;a href=&quot;/category/iradmusa_moharram&quot;&gt;Iradmusa&lt;/a&gt;&amp;nbsp;&amp;nbsp;
  &lt;/td&gt;
  &lt;td align=right&gt;
    Subject:
        &lt;a href=&quot;/category/graph_theory&quot;&gt;Graph Theory&lt;/a&gt;&amp;nbsp;&amp;nbsp;
  &lt;/td&gt;
&lt;/tr&gt;

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    &lt;table border=1 cellspacing=&quot;5&quot;&gt;
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        &lt;div class=&quot;envtheorem&quot;&gt;&lt;b&gt;Conjecture&lt;/b&gt;&amp;nbsp;&amp;nbsp; Let &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b8e7ad0330f925492bf468b5c379baec88cf1b3d.png&quot; alt=&quot;$ G $&quot; /&gt; be a graph and &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/c450c3185f7285cfa0b88d3a903c54f7df601201.png&quot; alt=&quot;$ k $&quot; /&gt; be a positive integer. The &lt;em&gt;&lt;img class=&quot;teximage&quot; src=&quot;/files/tex/43b5fd302d8f5ba143bb34369c40636c5feeb788.png&quot; alt=&quot;$ k- $&quot; /&gt;power of &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b8e7ad0330f925492bf468b5c379baec88cf1b3d.png&quot; alt=&quot;$ G $&quot; /&gt;&lt;/em&gt;, denoted by &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b048ddc696cdd8a621b159501fa5695e3fae99e8.png&quot; alt=&quot;$ G^k $&quot; /&gt;, is defined on the vertex set &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b324b54d8674fa66eb7e616b03c7a601ccdab6b8.png&quot; alt=&quot;$ V(G) $&quot; /&gt;, by connecting any two distinct vertices &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/e7ba5befcaa0d78e43b5176d70ce67425fd0fcdc.png&quot; alt=&quot;$ x $&quot; /&gt; and &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/739107c42bdb8452402d548efae98c3ce282847d.png&quot; alt=&quot;$ y $&quot; /&gt; with distance at most &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/c450c3185f7285cfa0b88d3a903c54f7df601201.png&quot; alt=&quot;$ k $&quot; /&gt;. In other words, &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/cd8a338d99bc211240133418299a99f45d85566d.png&quot; alt=&quot;$ E(G^k)=\{xy:1\leq d_G(x,y)\leq k\} $&quot; /&gt;. Also &lt;em&gt;&lt;img class=&quot;teximage&quot; src=&quot;/files/tex/43b5fd302d8f5ba143bb34369c40636c5feeb788.png&quot; alt=&quot;$ k- $&quot; /&gt;subdivision of &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b8e7ad0330f925492bf468b5c379baec88cf1b3d.png&quot; alt=&quot;$ G $&quot; /&gt;&lt;/em&gt;, denoted by &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/45627e469c3e3143a2f1499679bea01b7013d482.png&quot; alt=&quot;$ G^\frac{1}{k} $&quot; /&gt;, is constructed by replacing each edge &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/9530dc3006b9c8470f5e528b0d01c0cc9b574745.png&quot; alt=&quot;$ ij $&quot; /&gt; of &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b8e7ad0330f925492bf468b5c379baec88cf1b3d.png&quot; alt=&quot;$ G $&quot; /&gt; with a path of length &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/c450c3185f7285cfa0b88d3a903c54f7df601201.png&quot; alt=&quot;$ k $&quot; /&gt;. Note that for &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/ca53a4ec21e82327d0698fdf47e1dcf798650081.png&quot; alt=&quot;$ k=1 $&quot; /&gt;, we have &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/96c53e9d5e60fa2c160cb3b11ebb735aaee99b5b.png&quot; alt=&quot;$ G^\frac{1}{1}=G^1=G $&quot; /&gt;.&lt;br&gt; Now we can define the fractional power of a graph as follows:&lt;br&gt; Let &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b8e7ad0330f925492bf468b5c379baec88cf1b3d.png&quot; alt=&quot;$ G $&quot; /&gt; be a graph and &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/2d562ef5fbde200560d931d849894c9df0513426.png&quot; alt=&quot;$ m,n\in \mathbb{N} $&quot; /&gt;. The graph &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b971ba9ba6139f14f028cf60a78690e72c2c8b40.png&quot; alt=&quot;$ G^{\frac{m}{n}} $&quot; /&gt; is defined by the &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/64a6a47231dad79eba2f24c1f44a8944025c9190.png&quot; alt=&quot;$ m- $&quot; /&gt;power of the &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/9f4c49c23e585a667c6d943f0d97a3d2416385ae.png&quot; alt=&quot;$ n- $&quot; /&gt;subdivision of &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b8e7ad0330f925492bf468b5c379baec88cf1b3d.png&quot; alt=&quot;$ G $&quot; /&gt;. In other words &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/567dfd6e8bf6a80c1713f00fdf102fe2c37cec99.png&quot; alt=&quot;$ G^{\frac{m}{n}}\isdef (G^{\frac{1}{n}})^m $&quot; /&gt;.&lt;br&gt;  &lt;em&gt;Conjecture.&lt;/em&gt; Let &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/b8e7ad0330f925492bf468b5c379baec88cf1b3d.png&quot; alt=&quot;$ G $&quot; /&gt; be a connected graph with &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/c60c049e82d50db3238aff4614e5bd6fc62a2366.png&quot; alt=&quot;$ \Delta(G)\geq3 $&quot; /&gt; and &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/ddaab6dc091926fb1da549195000491cefae85c1.png&quot; alt=&quot;$ m $&quot; /&gt; be a positive integer greater than 1. Then for any positive integer &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/0bcf0bea4bd5d0169dff13d96d15269bb8e8cf09.png&quot; alt=&quot;$ n&amp;gt;m $&quot; /&gt;, we have &lt;img class=&quot;teximage&quot; src=&quot;/files/tex/891a81b310d1a25bb6a83e21c9c48cbe23864d58.png&quot; alt=&quot;$ \chi(G^{\frac{m}{n}})=\omega(G^\frac{m}{n}) $&quot; /&gt;.&lt;br&gt; In [1], it was shown that this conjecture is true in some special cases. &lt;/div&gt;

      &lt;/tr&gt;&lt;/td&gt;
    &lt;/table&gt;
  &lt;/td&gt;
&lt;/tr&gt;
&lt;/table&gt;</description>
 <category domain="http://www.openproblemgarden.org/category/iradmusa_moharram">Iradmusa, Moharram</category>
 <category domain="http://www.openproblemgarden.org/category/chromatic_number_fractional_power_of_graph_clique_number">chromatic number, fractional power of graph, clique number</category>
 <category domain="http://www.openproblemgarden.org/category/graph_theory">Graph Theory</category>
 <comments>http://www.openproblemgarden.org/op/vertex_coloring_of_graph_fractional_powers#comment</comments>
 <pubDate>Sat, 23 Apr 2011 17:11:02 +0200</pubDate>
 <dc:creator>Iradmusa</dc:creator>
 <guid isPermaLink="false">37316 at http://www.openproblemgarden.org</guid>
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