Split Casimir operator for simple Lie algebras in the cube of $\mathsf{a}\mathsf{d}$-representation and Vogel parameters

We constructed characteristic identities for the 3-split (polarized) Casimir operators of simple Lie algebras in the adjoint representations $\mathsf{a}\mathsf{d}$ and deduced a certain class of subrepresentations in ${\mathsf{a}\mathsf{d}}^{\otimes 3}$. The projectors onto invariant subspaces for these subrepresentations were directly constructed from the characteristic identities for the 3-split Casimir operators. For all simple Lie algebras, universal expressions for the traces of higher powers of the 3-split Casimir operators were found and dimensions of the subrepresentations in ${\mathsf{a}\mathsf{d}}^{\otimes 3}$ were calculated. All our formulas are in agreement with the universal description of (irreducible) subrepresentations in ${\mathsf{a}\mathsf{d}}^{\otimes 3}$ for simple Lie algebras in terms of the Vogel parameters.