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<div class="ChapSects" ><a href="chap2_mj.html#X78D8803A84DB6CE8" >2 <span class="Heading" >Obtaining Core-Free Subgroups</span ></a>
<div class="ContSect" ><span class="tocline" ><span class="nocss" > </span ><a href="chap2_mj.html#X79EF503F837B7702" >2.1 <span class="Heading" >Core-Free Subgroups</span ></a>
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<div class="ContSSBlock" >
<span class="ContSS" ><br /><span class="nocss" > </span ><a href="chap2_mj.html#X7A9042C27F0BA85B" >2.1-1 IsCoreFree</a></span >
<span class="ContSS" ><br /><span class="nocss" > </span ><a href="chap2_mj.html#X7D0391668782765C" >2.1-2 CoreFreeConjugacyClassesSubgroups</a></span >
<span class="ContSS" ><br /><span class="nocss" > </span ><a href="chap2_mj.html#X821F9BD687383C1F" >2.1-3 AllCoreFreeSubgroups</a></span >
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<div class="ContSect" ><span class="tocline" ><span class="nocss" > </span ><a href="chap2_mj.html#X847B222E84342E88" >2.2 <span class="Heading" >Degrees of Core-Free subgroups</span ></a>
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<div class="ContSSBlock" >
<span class="ContSS" ><br /><span class="nocss" > </span ><a href="chap2_mj.html#X844F04457C6EDC67" >2.2-1 CoreFreeDegrees</a></span >
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<h3>2 <span class="Heading" >Obtaining Core-Free Subgroups</span ></h3>
<p><a id="X79EF503F837B7702" name="X79EF503F837B7702" ></a></p>
<h4>2.1 <span class="Heading" >Core-Free Subgroups</span ></h4>
<p>A core-free subgroup is a subgroup in which its (normal) core is trivial.</p>
<p><a id="X7A9042C27F0BA85B" name="X7A9042C27F0BA85B" ></a></p>
<h5>2.1-1 IsCoreFree</h5>
<div class="func" ><table class="func" width="100%" ><tr ><td class="tdleft" ><code class="func" >‣ IsCoreFree</code >( <var class="Arg" >G</var >, <var class="Arg" >H</var > )</td ><td class="tdright" >( function )</td ></tr ></table ></div >
<p>Returns: a boolean</p>
<p>Given a group <var class="Arg" >G</var > and one of its subgroups <var class="Arg" >H</var >, it returns whether <var class="Arg" >H</var > is core-free in <var class="Arg" >G</var >.</p>
<div class="example" ><pre >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >G := SymmetricGroup(4);; H := Subgroup(G, [(1,3)(2,4)]);;</span >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >Core(G,H);</span >
Group(())
<span class="GAPprompt" >gap></span > <span class="GAPinput" >IsCoreFree(G,H);</span >
true
<span class="GAPprompt" >gap></span > <span class="GAPinput" >H := Subgroup(G, [(1,4)(2,3), (1,3)(2,4)]);;</span >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >IsCoreFree(G,H);</span >
false
<span class="GAPprompt" >gap></span > <span class="GAPinput" >Core(G,H);# H is a normal subgroup of G, hence it does not have a trivial core</span >
Group([ (1,4)(2,3), (1,3)(2,4) ])
</pre ></div >
<p><a id="X7D0391668782765C" name="X7D0391668782765C" ></a></p>
<h5>2.1-2 CoreFreeConjugacyClassesSubgroups</h5>
<div class="func" ><table class="func" width="100%" ><tr ><td class="tdleft" ><code class="func" >‣ CoreFreeConjugacyClassesSubgroups</code >( <var class="Arg" >G</var > )</td ><td class="tdright" >( function )</td ></tr ></table ></div >
<p>Returns: a list</p>
<p>Returns a list of all conjugacy classes of core-free subgroups of <var class="Arg" >G</var ></p>
<div class="example" ><pre >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >G := SymmetricGroup(4);; dh := DihedralGroup(10);;</span >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >cfccs := CoreFreeConjugacyClassesSubgroups(G);; Size(cfccs);</span >
7
<span class="GAPprompt" >gap></span > <span class="GAPinput" >cfccs_dh := CoreFreeConjugacyClassesSubgroups(dh);; Size(cfccs_dh);</span >
2
</pre ></div >
<p><a id="X821F9BD687383C1F" name="X821F9BD687383C1F" ></a></p>
<h5>2.1-3 AllCoreFreeSubgroups</h5>
<div class="func" ><table class="func" width="100%" ><tr ><td class="tdleft" ><code class="func" >‣ AllCoreFreeSubgroups</code >( <var class="Arg" >G</var > )</td ><td class="tdright" >( function )</td ></tr ></table ></div >
<p>Returns: a list</p>
<p>Returns a list of all core-free subgroups of <var class="Arg" >G</var ></p>
<div class="example" ><pre >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >G := SymmetricGroup(4);; dh := DihedralGroup(10);;</span >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >acfs := AllCoreFreeSubgroups(G);; Size(acfs);</span >
24
<span class="GAPprompt" >gap></span > <span class="GAPinput" >acfs_dh := AllCoreFreeSubgroups(dh);; Size(acfs_dh);</span >
6
</pre ></div >
<p><a id="X847B222E84342E88" name="X847B222E84342E88" ></a></p>
<h4>2.2 <span class="Heading" >Degrees of Core-Free subgroups</span ></h4>
<p><a id="X844F04457C6EDC67" name="X844F04457C6EDC67" ></a></p>
<h5>2.2-1 CoreFreeDegrees</h5>
<div class="func" ><table class="func" width="100%" ><tr ><td class="tdleft" ><code class="func" >‣ CoreFreeDegrees</code >( <var class="Arg" >G</var > )</td ><td class="tdright" >( function )</td ></tr ></table ></div >
<p>Returns: a list</p>
<p>Returns a list of all possible degrees of faithful transitive permutation representations of <var class="Arg" >G</var >. The degrees of a faithful transitive permutation representation of <var class="Arg" >G</var > are the index of its core-free subgroups.</p>
<div class="example" ><pre >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >G := SymmetricGroup(4);; dh := DihedralGroup(10);;</span >
<span class="GAPprompt" >gap></span > <span class="GAPinput" >CoreFreeDegrees(G);</span >
[ 4, 6, 8, 12, 24 ]
<span class="GAPprompt" >gap></span > <span class="GAPinput" >CoreFreeDegrees(dh);</span >
[ 5, 10 ]
</pre ></div >
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