Cauchy problems related to integrable matrix hierarchies

We discuss the solvability of two Cauchy problems in matrix pseudodifferential operators. The first is associated with a set of matrix pseudodifferential operators of negative order, a prominent example being the set of strict integral operator parts of products of a solution $(L,\{U_\alpha\})$ of the $\mathbf h[\partial]$-hierarchy, where $\mathbf h$ is a maximal commutative subalgebra of $gl_n(\mathbb{C})$. We show that it can be solved in the case of compatibility completeness of the adopted setting. The second Cauchy problem is slightly more general and relates to a set of matrix pseudodifferential operators of order zero or less. The key example here is the collection of integral operator parts of the different products of a solution $\{V_\alpha\}$ of the strict $\mathbf h[\partial]$-hierarchy. This system is solvable if two properties hold{:} the Cauchy solvability in dimension $n$ and the compatibility completeness. Both conditions are shown to hold in the formal power series setting.