Abstract:
for a unitary operator $U=U_a\oplus U_s$ for a $C_0$-contraction $T$, for the unilateral shift $S$ and for the backward shift $S^*$ the multiplicity of its direct sum is calculated:
$$
\mu_{(U\oplus S^n\oplus S^{*m}\oplus T)}=\max\{\mu_{U_s}, n+\max\{\mu_{U_a}, \mu_T, 1-\delta_{m0}\}\},
$$
where $\delta_{m0}=1$ if $m=0$ and $\delta_{m0}=0$ при $m>0$.