Multiplicities in the mixed trace cocharacter sequence of two $3\times   3$ matrices
  We find explicitly the multiplicities in the (mixed) trace cocharacter sequence of two $3\times 3$ matrices over a field of characteristic 0 and show that asymptotically they behave as polynomials of seventh degree. As a consequence we obtain also the multiplicities of certain irreducible characters in the cocharacter sequence of the polynomial identities of $3\times 3$ matrices. 
Vesselin Drensky, Georgi K. Genov, and Angela Valenti