If minmodelLie (or extBasisLie or extTableLie) of a Lie algebra L is computed up to a certain degree, then the representation of ExtUL(k,k), where k is L.field, as linear polynomials may be obtained as L.cache.extRepRing.
i1 : L=lieAlgebra{a,b}/{a b} o1 = L o1 : LieAlgebra |
i2 : extBasisLie 3 o2 = {ext , ext , ext } 0 1 2 o2 : List |
i3 : E=L.cache.extRepRing o3 = E o3 : PolynomialRing |
i4 : (ext_0+2*ext_1) ext_1 o4 = -ext 2 o4 : E |
The object extRepRing is a symbol.