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2 The Commuting Graph
 2.1 CommGraph Main Functions

2 The Commuting Graph

2.1 CommGraph Main Functions

2.1-1 CommGraph
‣ CommGraph( group )( function )

This function receives a group as an input then utilizes the Grape package to implement a graph \((V,E)\) applying the following rule:

The vertices of this graph are the elements of the inputted group \(G\) and two vertices are connected if the elements commute

2.1-2 DeepCommGraph
‣ DeepCommGraph( group )( function )

This function receives a group as an input then utilizes the Grape package to implement a graph \((V,E)\) applying the following rule:

Two elements of \(G\) are joined in the deep commuting graph if and only if their preimages in every central extension of \(G\) (that is, every group \(H\) with a central subgroup \(Z\) such that \(H/Z \cong G\)) commute.

2.1-3 CommDegree
‣ CommDegree( group )( function )

The commutativity degree of a group is defined as the probability that two elements of the group commutes.

The CommDegree function receives a group as an input then outputs a number \(\text{CommDegree}(G) \in (\frac{5}{8}, 1)\) that represents this probability. If the group is abelian, then the commutative degree is 1. Otherwise it is always less than \(\frac{5}{8}\) as a consequence of the \(\frac{5}{8}\) lower bound theorem.

2.1-4 MaxAbelianSubgroup
‣ MaxAbelianSubgroup( group )( function )

This function receives a group as an input then utilizes the Grape package function MaximumClique(graph) to return the group generated by a maximum clique of the group's commutative graph.

2.1-5 CommDegreeGroupFind
‣ CommDegreeGroupFind( group )( function )

This function receives an integer number \(n\) and then outputs a group \(G\) with commutativity degree \(\frac{1}{n}\).

2.1-6 PrimeCommDegreeGroupFind
‣ PrimeCommDegreeGroupFind( prime )( function )

The PrimeCommDegreeGroupFind function receives a prime number \(p\) and returns a group \(G\) with commutativity degree \(\frac{1}{p}\), the CommDegreeGroupFind function uses this function taking the prime factorization of the number \(n\) and taking the direct product of the groups with commmutativity degree equal to \(\frac{1}{p_i}\).

2.1-7 NilpotentCommDegreeGroupFind
‣ NilpotentCommDegreeGroupFind( number )( function )

Similar to the PrimeCommDegreeGroupFind, but returning a nilpotent group with commutativity degree less than \(\frac{1}{n}\) given an integer number \(n\).

2.1-8 NilpotentPrimeCommDegreeGroupFind
‣ NilpotentPrimeCommDegreeGroupFind( prime )( function )

Similar to the PrimeCommDegreeGroupFind, but returning a nilpotent group with commutativity degree less than \(\frac{1}{p}\) given a prime number \(p\).

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