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6 Relatively free Algebras
 6.1 Computing Kurosh Algebras
 6.2 A Library of Kurosh Algebras
 6.3 Example of accessing the library of Kurosh algebras

6 Relatively free Algebras

As described in [Eic11], the nilpotent quotient algorithm can also be used to determine certain relatively free algebras; that is, algebras that are free within a variety.

6.1 Computing Kurosh Algebras

6.1-1 KuroshAlgebra
‣ KuroshAlgebra( d, n, F )( function )

determines a nilpotent table for the largest associative algebra on \(d\) generators over the field \(F\) so that every element \(a\) of the algebra satisfies \(a^n = 0\).

6.1-2 ExpandExponentLaw
‣ ExpandExponentLaw( T, n )( function )

suppose that \(T\) is the nilpotent table of a Kurosh algebra of exponent \(n\) defined over a prime field. This function determines polynomials describing the corresponding Kurosh algebras over all fields with the same characteristic as the prime field.

6.2 A Library of Kurosh Algebras

The package contains a library of Kurosh algebras. This can be accessed as follows.

6.2-1 KuroshAlgebraByLib
‣ KuroshAlgebraByLib( d, n, F )( function )

At present, the library contains the Kurosh algebras for \(n=2\), \((d,n) = (2,3)\), \((d,n) = (3,3)\) and \(F = ℚ\) or \(|F| \in \{2,3,4\}\), \((d,n) = (4,3)\) and \(F = ℚ\) or \(|F| \in \{2,3,4\}\), \((d,n) = (2,4)\) and \(F = ℚ\) or \(|F| \in \{2,3,4,9\}\), \((d,n) = (2,5)\) and \(F = ℚ\) or \(|F| \in \{2,3,4,5,8,9\}\).

6.3 Example of accessing the library of Kurosh algebras

gap> KuroshAlgebra(2,2,Rationals);
... some printout ..
rec( bas := [ [ 1, 0, 0, 0 ], [ 0, 1, 1, 0 ], [ 0, 0, 0, 1 ], [ 0, 1, 0, 0 ] ]
    , com := false, dim := 3, fld := Rationals, rnk := 2, 
  tab := [ [ [ 0, 0, 0 ], [ 0, 0, -1 ], [ 0, 0, 0 ] ], 
      [ [ 0, 0, 1 ], [ 0, 0, 0 ], [ 0, 0, 0 ] ] ], wds := [ ,, [ 2, 1 ] ], 
  wgs := [ 1, 1, 2 ] )

 

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