Dear community of GTPack,

First, I’d like to thank the authors of this amazing software.

We are a group of researcher that are using your library for some simulation in representation theory.

While using the library we noted that some instances of the Clebsh-Gordan coefficients computed from your library were actually absent. (i.e. the function returned an empty list)

We understood that this is because a numerical error in floating points operations. The patch is the following.

In the file “RepresentationTheory.m”, in the function “GTClebschGordanCoefficients”, after the line:

Es = Eigensystem[Simplify@A[1, 1]];

It suffices to add the function Round[] in the definition of npq.

npq = Round[Sum[Es[[1, i]], {i, 1, dp}]];

In certain instances, the biggest eigenvalue is slightly smaller than 1, and thus the Table construct

CGK = Table[Table[A[i, 1] . Es[[2, a]], {i, 1, d3}], {a, 1, npq}];

Is never executed, as npq is strictly smaller than 1.

Hope this helps.

Matthias Geilhufe Answered question 30. November 2021